TY - JOUR
A1 - Rothe, Martin
A1 - Zhao, Yuhang
A1 - Müller, Johannes
A1 - Kewes, Günter
A1 - Koch, Christoph T.
A1 - Lu, Yan
A1 - Benson, Oliver
T1 - Self-assembly of plasmonic nanoantenna-waveguide structures for subdiffractional chiral sensing
JF - ACS nano
N2 - Spin-momentum locking is a peculiar effect in the near-field of guided optical or plasmonic modes. It can be utilized to map the spinning or handedness of electromagnetic fields onto the propagation direction. This motivates a method to probe the circular dichroism of an illuminated chiral object. In this work, we demonstrate local, subdiffraction limited chiral coupling of light and propagating surface plasmon polaritons in a self-assembled system of a gold nanoantenna and a silver nanowire. A thin silica shell around the nanowire provides precise distance control and also serves as a host for fluorescent molecules, which indicate the direction of plasmon propagation. We characterize our nanoantenna-nanowire systems comprehensively through correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging. Three-dimensional numerical simulations support the experimental findings. Besides our measurement of far-field polarization, we estimate sensing capabilities and derive not only a sensitivity of 1 mdeg for the ellipticity of the light field, but also find 10(3) deg cm(2)/dmol for the circular dichroism of an analyte locally introduced in the hot spot of the antenna-wire system. Thorough modeling of a prototypical design predicts on-chip sensing of chiral analytes. This introduces our system as an ultracompact sensor for chiral response far below the diffraction limit.
KW - plasmonics
KW - nanoparticle assemblies
KW - core-shell
KW - spin-orbit coupling
KW - chirality
KW - circular dichroism
KW - nano-optics
Y1 - 2021
U6 - https://doi.org/10.1021/acsnano.0c05240
SN - 1936-0851
SN - 1936-086X
VL - 15
IS - 1
SP - 351
EP - 361
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Lau, Skadi
A1 - Liu, Yue
A1 - Maier, Anna
A1 - Braune, Steffen
A1 - Gossen, Manfred
A1 - Neffe, Axel T.
A1 - Lendlein, Andreas
T1 - Establishment of an in vitro thrombogenicity test system with cyclic olefin copolymer substrate for endothelial layer formation
JF - MRS communications / a publication of the Materials Research Society
N2 - In vitro thrombogenicity test systems require co-cultivation of endothelial cells and platelets under blood flow-like conditions. Here, a commercially available perfusion system is explored using plasma-treated cyclic olefin copolymer (COC) as a substrate for the endothelial cell layer. COC was characterized prior to endothelialization and co-cultivation with platelets under static or flow conditions. COC exhibits a low roughness and a moderate hydrophilicity. Flow promoted endothelial cell growth and prevented platelet adherence. These findings show the suitability of COC as substrate and the importance of blood flow-like conditions for the assessment of the thrombogenic risk of drugs or cardiovascular implant materials.
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00072-6
SN - 2159-6867
VL - 11
IS - 5
SP - 559
EP - 567
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Tung, Wing Tai
A1 - Sun, Xianlei
A1 - Wang, Weiwei
A1 - Xu, Xun
A1 - Ma, Nan
A1 - Lendlein, Andreas
T1 - Structure, mechanical properties and degradation behavior of electrospun PEEU fiber meshes and films
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - The capability of a degradable implant to provide mechanical support depends on its degradation behavior. Hydrolytic degradation was studied for a polyesteretherurethane (PEEU70), which consists of poly(p-dioxanone) (PPDO) and poly(epsilon-caprolactone) (PCL) segments with a weight ratio of 70:30 linked by diurethane junction units. PEEU70 samples prepared in the form of meshes with average fiber diameters of 1.5 mu m (mesh1.5) and 1.2 mu m (mesh1.2), and films were sterilized and incubated in PBS at 37 degrees C with 5 vol% CO2 supply for 1 to 6 weeks. Degradation features, such as cracks or wrinkles, became apparent from week 4 for all samples. Mass loss was found to be 11 wt%, 6 wt%, and 4 wt% for mesh1.2, mesh1.5, and films at week 6. The elongation at break decreased to under 20% in two weeks for mesh1.2. In case of the other two samples, this level of degradation was achieved after 4 weeks. The weight average molecular weight of both PEEU70 mesh and film samples decreased to below 30 kg/mol when elongation at break dropped below 20%. The time period of sustained mechanical stability of PEEU70-based meshes depends on the fiber diameter and molecular weight.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-020-00001-0
SN - 2059-8521
VL - 6
IS - 10
SP - 276
EP - 282
PB - Springer Nature Switzerland AG
CY - Cham
ER -
TY - JOUR
A1 - Zhao, Yuhang
A1 - Opitz, Andreas
A1 - Eljarrat, Alberto
A1 - Kochovski, Zdravko
A1 - Koch, Christoph
A1 - Koch, Norbert
A1 - Lu, Yan
T1 - Kinetic study on the adsorption of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane on Ag nanoparticles in chloroform
BT - implications for the charge transfer complex of Ag-F(4)TCNQ
JF - ACS applied nano materials
N2 - In this study, the kinetics of the adsorption of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) on the surface of Ag nanoparticles (Ag NPs) in chloroform has been intensively investigated, as molecular doping is known to play a crucial role in organic electronic devices. Based on the results obtained from UV-visible (vis)-near-infrared (NIR) absorption spectroscopy, cryogenic transmission electron microscopy, scanning nanobeam electron diffraction, and electron energy loss spectroscopy, a two-step interaction kinetics has been proposed for the Ag NPs and F(4)TCNQ molecules, which includes the first step of electron transfer from Ag NPs to F(4)TCNQ indicated by the ionization of F(4)TCNQ and the second step of the formation of a Ag-F(4)TCNQ complex. The whole process has been followed via UV-vis-NIR absorption spectroscopy, which reveals distinct kinetics at two stages: the instantaneous ionization and the long-term complex formation. The kinetics and the influence of the molar ratio of Ag NPs/F(4)TCNQ molecules on the interaction between Ag NPs and F(4)TCNQ molecules in an organic solution are reported herein for the first time. Furthermore, the control experiment with silica-coated Ag NPs manifests that the charge transfer at the surface between Ag NPs and F(4)TCNQ molecules is prohibited by a silica layer of 18 nm.
KW - Ag nanoparticles
KW - F(4)TCNQ
KW - phase transfer
KW - kinetics
KW - electron transfer
KW - surface interaction
Y1 - 2021
U6 - https://doi.org/10.1021/acsanm.1c02153
SN - 2574-0970
VL - 4
IS - 11
SP - 11625
EP - 11635
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Zhou, Shuo
A1 - Xu, Xun
A1 - Ma, Nan
A1 - Jung, Friedrich
A1 - Lendlein, Andreas
T1 - Influence of sterilization conditions on sulfate-functionalized polyGGE
JF - Clinical hemorheology and microcirculation : blood flow and vessels
N2 - Sulfated biomolecules are known to influence numerous biological processes in all living organisms. Particularly, they contribute to prevent and inhibit the hypercoagulation condition. The failure of polymeric implants and blood contacting devices is often related to hypercoagulation and microbial contamination. Here, bioactive sulfated biomacromolecules are mimicked by sulfation of poly(glycerol glycidyl ether) (polyGGE) films. Autoclaving, gamma-ray irradiation and ethylene oxide (EtO) gas sterilization techniques were applied to functionalized materials. The sulfate group density and hydrophilicity of sulfated polymers were decreased while chain mobility and thermal degradation were enhanced post autoclaving when compared to those after EtO sterilization. These results suggest that a quality control after sterilization is mandatory to ensure the amount and functionality of functionalized groups are retained.
KW - Sulfated polymer
KW - sulfation
KW - sterilization
KW - ethylene oxide
Y1 - 2021
U6 - https://doi.org/10.3233/CH-211241
SN - 1386-0291
SN - 1875-8622
VL - 79
IS - 4
SP - 597
EP - 608
PB - IOS Press
CY - Amsterdam
ER -
TY - JOUR
A1 - Breternitz, Joachim
A1 - Schorr, Susan
T1 - Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc2(1)
JF - Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances
N2 - Binary III-V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on this matter. The non-existence of compounds crystallizing in Pmc2(1), formally the highest subgroup of the wurtzite type fulfilling Pauling's rules for 1:1:2 stoichiometries, has been puzzling scientists for a while; a rationalization is given, from a crystallographic basis, of why this space group is unlikely to be adopted.
KW - group-subgroup relationships
KW - nitride materials
KW - wurtzite type
Y1 - 2021
U6 - https://doi.org/10.1107/S2053273320015971
SN - 2053-2733
VL - 77
IS - 3
SP - 208
EP - 216
PB - Blackwell
CY - Oxford [u.a.]
ER -
TY - JOUR
A1 - Haubitz, Toni
A1 - Drobot, Björn
A1 - Tsushima, Satoru
A1 - Steudtner, Robin
A1 - Stumpf, Thorsten
A1 - Kumke, Michael Uwe
T1 - Quenching mechanism of uranyl(VI) by chloride and bromide in aqueous and non-aqueous solutions
JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2 - A major hindrance in utilizing uranyl(VI) luminescence as a standard analytical tool, for example, in environmental monitoring or nuclear industries, is quenching by other ions such as halide ions, which are present in many relevant matrices of uranyl(VI) speciation. Here, we demonstrate through a combination of time-resolved laser-induced fluorescence spectroscopy, transient absorption spectroscopy, and quantum chemistry that coordinating solvent molecules play a crucial role in U(VI) halide luminescence quenching. We show that our previously suggested quenching mechanism based on an internal redox reaction of the 1:2-uranyl-halide-complex holds also true for bromide-induced quenching of uranyl(VI). By adopting specific organic solvents, we were able to suppress the separation of the oxidized halide ligand X-2(center dot-) and the formed uranyl(V) into fully solvated ions, thereby "reigniting" U(VI) luminescence. Time-dependent density functional theory calculations show that quenching occurs through the outer-sphere complex of U(VI) and halide in water, while the ligand-to-metal charge transfer is strongly reduced in acetonitrile.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jpca.1c02487
SN - 1089-5639
SN - 1520-5215
VL - 125
IS - 20
SP - 4380
EP - 4389
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Geiger, Christina
A1 - Reitenbach, Julija
A1 - Henschel, Cristiane
A1 - Kreuzer, Lucas
A1 - Widmann, Tobias
A1 - Wang, Peixi
A1 - Mangiapia, Gaetano
A1 - Moulin, Jean-François
A1 - Papadakis, Christine M.
A1 - Laschewsky, André
A1 - Müller-Buschbaum, Peter
T1 - Ternary nanoswitches realized with multiresponsive PMMA-b-PNIPMAM films in mixed water/acetone vapor atmospheres
JF - Advanced engineering materials
N2 - To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character.
KW - co-nonsolvency
KW - diblock copolymers
KW - nanoswitches
KW - neutron reflectometry
KW - thin films
Y1 - 2021
U6 - https://doi.org/10.1002/adem.202100191
SN - 1438-1656
SN - 1527-2648
VL - 23
IS - 11
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Melani, Giacomo
A1 - Nagata, Yuki
A1 - Saalfrank, Peter
T1 - Vibrational energy relaxation of interfacial OH on a water-covered alpha-Al2O3(0001) surface
BT - a non-equilibrium ab initio molecular dynamics study
JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2 - Vibrational relaxation of adsorbates is a sensitive tool to probe energy transfer at gas/solid and liquid/solid interfaces. The most direct way to study relaxation dynamics uses time-resolved spectroscopy. Here we report on a non-equilibrium ab initio molecular dynamics (NE-AIMD) methodology to model vibrational relaxation of OH vibrations on a hydroxylated, water-covered alpha-Al2O3(0001) surface. In our NE-AIMD approach, after exciting selected O-H bonds their coupling to surface phonons and to the water adlayer is analyzed in detail, by following both the energy flow in time, as well as the time-evolution of Vibrational Density of States (VDOS) curves. The latter are obtained from Time-dependent Correlation Functions (TCFs) and serve as prototypical, generic representatives of time-resolved vibrational spectra. As most important results, (i) we find a few-picosecond lifetime of the excited modes and (ii) identify both hydrogen-bonded aluminols and water molecules in the adsorbed water layer as main dissipative channels, while the direct coupling to Al2O3 surface phonons is of minor importance on the timescales of interest. Our NE-AIMD/TCF methodology is powerful for complex adsorbate systems, in principle even reacting ones, and opens a way towards time-resolved vibrational spectroscopy.
Y1 - 2021
U6 - https://doi.org/10.1039/d0cp03777j
SN - 1463-9076
SN - 1463-9084
VL - 23
IS - 13
SP - 7714
EP - 7723
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Wang, Zhenyu
A1 - Fritsch, Daniel
A1 - Berendts, Stefan
A1 - Lerch, Martin
A1 - Breternitz, Joachim
A1 - Schorr, Susan
T1 - Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis
JF - Chemical science / RSC, Royal Society of Chemistry
N2 - Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials.
Y1 - 2021
U6 - https://doi.org/10.1039/d1sc00328c
SN - 2041-6539
VL - 12
IS - 24
SP - 8493
EP - 8500
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Saeedi Garakani, Sadaf
A1 - Xie, Dongjiu
A1 - Khorsand Kheirabad, Atefeh
A1 - Lu, Yan
A1 - Yuan, Jiayin
T1 - Template-synthesis of a poly(ionic liquid)-derived Fe1-xS/nitrogen-doped porous carbon membrane and its electrode application in lithium-sulfur batteries
JF - Materials advances
N2 - This study deals with the facile synthesis of Fe1-xS nanoparticle-containing nitrogen-doped porous carbon membranes (denoted as Fe1-xS/N-PCMs) via vacuum carbonization of hybrid porous poly(ionic liquid) (PIL) membranes, and their successful use as a sulfur host material to mitigate the shuttle effect in lithium-sulfur (Li-S) batteries. The hybrid porous PIL membranes as the sacrificial template were prepared via ionic crosslinking of a cationic PIL with base-neutralized 1,1 '-ferrocenedicarboxylic acid, so that the iron source was molecularly incorporated into the template. The carbonization process was investigated in detail at different temperatures, and the chemical and porous structures of the carbon products were comprehensively analyzed. The Fe1-xS/N-PCMs prepared at 900 degrees C have a multimodal pore size distribution with a satisfactorily high surface area and well-dispersed iron sulfide nanoparticles to physically and chemically confine the LiPSs. The sulfur/Fe1-xS/N-PCM composites were then tested as electrodes in Li-S batteries, showing much improved capacity, rate performance and cycle stability, in comparison to iron sulfide-free, nitrogen-doped porous carbon membranes.
Y1 - 2021
U6 - https://doi.org/10.1039/d1ma00441g
SN - 2633-5409
VL - 2
IS - 15
SP - 5203
EP - 5212
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Xu, Xun
A1 - Nie, Yan
A1 - Wang, Weiwei
A1 - Ma, Nan
A1 - Lendlein, Andreas
T1 - Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells
JF - MRS communications / a publication of the Materials Research Society
N2 - Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs.
KW - Actuation
KW - Antiviral
KW - Biomaterial
KW - COVID-19
KW - Shape memory
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00049-5
SN - 2159-6867
VL - 11
IS - 4
SP - 425
EP - 431
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Deng, Zijun
A1 - Wang, Weiwei
A1 - Xu, Xun
A1 - Ma, Nan
A1 - Lendlein, Andreas
T1 - Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin beta 1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00091-4
SN - 2059-8521
VL - 6
IS - 31
SP - 739
EP - 744
PB - Springer Nature Switzerland AG
CY - Cham
ER -
TY - JOUR
A1 - Machatschek, Rainhard Gabriel
A1 - Saretia, Shivam
A1 - Lendlein, Andreas
T1 - Assessing the influence of temperature-memory creation on the degradation of copolyesterurethanes in ultrathin films
JF - Advanced materials interfaces
N2 - Copolyesterurethanes (PDLCLs) based on oligo(epsilon-caprolactone) (OCL) and oligo(omega-pentadecalactone) (OPDL) segments are biodegradable thermoplastic temperature-memory polymers. The temperature-memory capability in these polymers with crystallizable control units is implemented by a thermomechanical programming process causing alterations in the crystallite arrangement and chain organization. These morphological changes can potentially affect degradation. Initial observations on the macroscopic level inspire the hypothesis that switching of the controlling units causes an accelerated degradation of the material, resulting in programmable degradation by sequential coupling of functions. Hence, detailed degradation studies on Langmuir films of a PDLCL with 40 wt% OPDL content are carried out under enzymatic catalysis. The temperature-memory creation procedure is mimicked by compression at different temperatures. The evolution of the chain organization and mechanical properties during the degradation process is investigated by means of polarization-modulated infrared reflection absorption spectroscopy, interfacial rheology and to some extend by X-ray reflectivity. The experiments on PDLCL Langmuir films imply that degradability is not enhanced by thermal switching, as the former depends on the temperature during cold programming. Nevertheless, the thin film experiments show that the leaching of OCL segments does not induce further crystallization of the OPDL segments, which is beneficial for a controlled and predictable degradation.
KW - block copolymers
KW - degradation
KW - Langmuir monolayers
KW - rheology
KW - temperature-memory polymers
Y1 - 2021
U6 - https://doi.org/10.1002/admi.202001926
SN - 2196-7350
VL - 8
IS - 6
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Kreuzer, Lucas
A1 - Widmann, Tobias
A1 - Geiger, Christina
A1 - Wang, Peixi
A1 - Vagias, Apostolos N.
A1 - Heger, Julian Eliah
A1 - Haese, Martin
A1 - Hildebrand, Viet
A1 - Laschewsky, André
A1 - Papadakis, Christine M.
A1 - Müller-Buschbaum, Peter
T1 - Salt-dependent phase transition behavior of doubly thermoresponsive poly(sulfobetaine)-based diblock copolymer thin films
JF - Langmuir : the ACS journal of surfaces and colloids / American Chemical Society
N2 - The water vapor-induced swelling, as well as subsequent phase-transition kinetics, of thin films of a diblock copolymer (DBC) loaded with different amounts of the salt NaBr, is investigated in situ. In dilute aqueous solution, the DBC features an orthogonally thermoresponsive behavior. It consists of a zwitterionic poly(sulfobetaine) block, namely, poly(4-(N-(3'-methacrylamidopropyl)-N, N-dimethylammonio) butane-1-sulfonate) (PSBP), showing an upper critical solution temperature, and a nonionic block, namely, poly(N-isopropylmethacrylamide) (PNIPMAM), exhibiting a lower critical solution temperature. The swelling kinetics in D2O vapor at 15 degrees C and the phase transition kinetics upon heating the swollen film to 60 degrees C and cooling back to 15 degrees C are followed with simultaneous time-of-flight neutron reflectometry and spectral reflectance measurements. These are complemented by Fourier transform infrared spectroscopy. The collapse temperature of PNIPMAM and the swelling temperature of PSBP are found at lower temperatures than in aqueous solution, which is attributed to the high polymer concentration in the thin-film geometry. Upon inclusion of sub-stoichiometric amounts (relative to the monomer units) of NaBr in the films, the water incorporation is significantly increased. This increase is mainly attributed to a salting-in effect on the zwitterionic PSBP block. Whereas the addition of NaBr notably shifts the swelling temperature of PSBP to lower temperatures, the collapse temperature of PNIPMAM remains unaffected by the presence of salt in the films.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.langmuir.1c01342
SN - 0743-7463
SN - 1520-5827
VL - 37
IS - 30
SP - 9179
EP - 9191
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Neffe, Axel T.
A1 - Löwenberg, Candy
A1 - Julich-Gruner, Konstanze K.
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Thermally-induced shape-memory behavior of degradable gelatin-based networks
JF - International journal of molecular sciences
N2 - Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) alpha,omega-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27-23 kPa and Young's moduli of 215-360 kPa at 4 degrees C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 degrees C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates R-r close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.
KW - shape-memory hydrogel
KW - active polymer
KW - biopolymer
KW - mechanical
KW - properties
KW - degradation
Y1 - 2021
U6 - https://doi.org/10.3390/ijms22115892
SN - 1422-0067
SN - 1661-6596
VL - 22
IS - 11
PB - Molecular Diversity Preservation International
CY - Basel
ER -
TY - JOUR
A1 - Bochove, Bas van
A1 - Grijpma, Dirk W.
A1 - Lendlein, Andreas
A1 - Seppälä, Jukka
T1 - Designing advanced functional polymers for medicine
JF - European polymer journal : EPJ
Y1 - 2021
U6 - https://doi.org/10.1016/j.eurpolymj.2021.110573
SN - 0014-3057
VL - 155
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Hwang, Jinyeon
A1 - Zhang, Wuyong
A1 - Youk, Sol
A1 - Schutjajew, Konstantin
A1 - Oschatz, Martin
T1 - Understanding structure-property relationships under experimental conditions for the optimization of lithium-ion capacitor anodes based on all-carbon-composite materials
JF - Energy technology : generation, conversion, storage, distribution
N2 - The nanoscale combination of a conductive carbon and a carbon-based material with abundant heteroatoms for battery electrodes is a method to overcome the limitation that the latter has high affinity to alkali metal ions but low electronic conductivity. The synthetic protocol and the individual ratios and structures are important aspects influencing the properties of such multifunctional compounds. Their interplay is, herein, investigated by infiltration of a porous ZnO-templated carbon (ZTC) with nitrogen-rich carbon obtained by condensation of hexaazatriphenylene-hexacarbonitrile (HAT-CN) at 550-1000 degrees C. The density of lithiophilic sites can be controlled by HAT-CN content and condensation temperature. Lithium storage properties are significantly improved in comparison with those of the individual compounds and their physical mixtures. Depending on the uniformity of the formed composite, loading ratio and condensation temperature have different influence. Most stable operation at high capacity per used monomer is achieved with a slowly dried composite with an HAT-CN:ZTC mass ratio of 4:1, condensed at 550 degrees C, providing more than 400 mAh g(-1) discharge capacity at 0.1 A g(-1) and a capacity retention of 72% after 100 cycles of operation at 0.5 A g(-1) due to the homogeneity of the composite and high content of lithiophilic sites.
KW - anodes
KW - hybrid materials
KW - nitrogen-doped carbon
KW - porous carbon
KW - lithium-ion capacitors
Y1 - 2021
U6 - https://doi.org/10.1002/ente.202001054
SN - 2194-4296
VL - 9
IS - 3
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Kreuzer, Lucas
A1 - Lindenmeir, Christoph
A1 - Geiger, Christina
A1 - Widmann, Tobias
A1 - Hildebrand, Viet
A1 - Laschewsky, André
A1 - Papadakis, Christine M.
A1 - Müller-Buschbaum, Peter
T1 - Poly(sulfobetaine) versus poly(N-isopropylmethacrylamide)
BT - co-nonsolvency-type behavior of thin films in a water/methanol atmosphere
JF - Macromolecules : a publication of the American Chemical Society
N2 - The swelling and co-nonsolvency behaviors in pure H2O and in a mixed H2O/CH3OH vapor atmosphere of two different polar, water-soluble polymers in thin film geometry are studied in situ. Films of a zwitterionic poly(sulfobetaine), namely, poly[3-((2-(methacryloyloxy)ethyl)dimethylammonio) propane-1-sulfonate] (PSPE), and a polar nonionic polymer, namely, poly(N-isopropylmethacrylamide) (PNIPMAM), are investigated in real time by spectral reflectance (SR) measurements and Fourier transform infrared (FTIR) spectroscopy. Whereas PSPE is insoluble in methanol, PNIPMAM is soluble but exhibits cononsolvency behavior in water/methanol mixtures. First, the swelling of PSPE and PNIPMAM thin films in H2O vapor is followed. Subsequently, CH3OH is added to the vapor atmosphere, and its contracting effect on the water-swollen films is monitored, revealing a co-nonsolvency-type behavior for PNIPMAM and PSPE. SR measurements indicate that PSPE and PNIPMAM behave significantly different during the H2O swelling and subsequent exposure to CH3OH, not only with respect to the amounts of absorbed water and CH3OH, but also to the cosolvent-induced contraction mechanisms. While PSPE thin films exhibit an abrupt one-step contraction, the contraction of PNIPMAM thin films occurs in two steps. FTIR studies corroborate these findings on a molecular scale and reveal the role of the specific functional groups, both during the swelling and the cosolvent-induced switching of the solvation state.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.macromol.0c02281
SN - 0024-9297
SN - 1520-5835
VL - 54
IS - 3
SP - 1548
EP - 1556
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Saretia, Shivam
A1 - Machatschek, Rainhard Gabriel
A1 - Lendlein, Andreas
T1 - Degradation kinetics of oligo(ε-caprolactone) ultrathin films
BT - Influence of crystallinity
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - The potential of using crystallinity as morphological parameter to control polyester degradation in acidic environments is explored in ultrathin films by Langmuir technique. Films of hydroxy or methacrylate end-capped oligo(epsilon-caprolactone) (OCL) are prepared at the air-water interface as a function of mean molecular area (MMA). The obtained amorphous, partially crystalline or highly crystalline ultrathin films of OCL are hydrolytically degraded at pH similar to 1.2 on water surface or on silicon surface as-transferred films. A high crystallinity reduces the hydrolytic degradation rate of the films on both water and solid surfaces. Different acceleration rates of hydrolytic degradation of semi-crystalline films are achieved either by crystals complete melting, partially melting, or by heating them below their melting temperatures. Semi-crystalline OCL films transferred via water onto a solid surface retain their crystalline morphology, degrade in a controlled manner, and are of interest as thermoswitchable coatings for cell substrates and medical devices.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00067-4
SN - 2059-8521
VL - 6
IS - 33
SP - 790
EP - 795
PB - Springer Nature Switzerland AG
CY - Cham
ER -
TY - JOUR
A1 - Folikumah, Makafui Y.
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Reaction behaviour of peptide-based single thiol-thioesters exchange reaction substrate in the presence of externally added thiols
JF - MRS communications / a publication of the Materials Research Society
N2 - Identification of patterns in chemical reaction pathways aids in the effective design of molecules for specific applications. Here, we report on model reactions with a water-soluble single thiol-thioester exchange (TTE) reaction substrate, which was designed taking in view biological and medical applications. This substrate consists of the thio-depsipeptide, Ac-Pro-Leu-Gly-SLeu-Leu-Gly-NEtSH (TDP) and does not yield foul-smelling thiol exchange products when compared with aromatic thiol containing single TTE substrates. TDP generates an alpha,omega-dithiol crosslinker in situ in a 'pseudo intramolecular' TTE. Competitive intermolecular TTE of TDP with externally added "basic" thiols increased the crosslinker concentration whilst "acidic" thiols decreased its concentration. TDP could potentially enable in situ bioconjugation and crosslinking applications.
KW - Biomaterials
KW - Biomimetic
KW - Mass spectrometry
KW - Nuclear magnetic resonance
KW - (NMR)
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00041-z
SN - 2159-6859
SN - 2159-6867
VL - 11
IS - 4
SP - 402
EP - 410
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Kleinpeter, Erich
A1 - Heydenreich, Matthias
A1 - Shainyan, Bagrat A.
T1 - At the experimental limit of the NMR conformational analysis
BT - Si-29 and C-13 NMR study of the conformational equilibrium of 1-phenyl-1-tert-butylsilacyclohexane
JF - Organic letters
N2 - The low temperature (95 K) NMR study of 1-Ph-1-t-Bu-silacyclohexane (1) showed the conformational equilibrium to be extremely one-sided toward thePh(ax),t-Bueq conformer. The barrier to interconversion has been measured (4.2-4.6 kcal/mol) and the conformational equilibrium [Delta nu = 1990.64 ppm (Si-29), 618.9 ppm (C-13), 1-Ph-ax:1-Pheq = (95.6-96.6%):(3.4-4.4%), K = 25 +/- 3, Delta G degrees = -RT ln K = 0.58-0.63 kcal/mol] analyzed. The assignment and quantification of the NMR signals is supported by MP2 and DFT calculations.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.orglett.0c03878
SN - 1523-7060
SN - 1523-7052
VL - 23
IS - 2
SP - 405
EP - 409
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Mawire, Phillip
A1 - Mozirandi, Winnie
A1 - Heydenreich, Matthias
A1 - Chi, Godloves Fru
A1 - Mukanganyama, Stanley
T1 - Isolation and antimicrobial activities of phytochemicals from Parinari curatellifolia (Chrysobalanaceae)
JF - Advances in pharmacological and pharmaceutical sciences
N2 - The widespread use of antimicrobial agents to treat infectious diseases has led to the emergence of antibiotic resistant pathogens. Plants have played a central role in combating many ailments in humans, and Parinari curatellifolia has been used for medicinal purposes. Seven extracts from P. curatellifolia leaves were prepared using serial exhaustive extraction of nonpolar to polar solvents. The microbroth dilution method was used to evaluate antimicrobial bioactivities of extracts. Five of the extracts were significantly active against at least one test microbe. Mycobacterium smegmatis was the most susceptible to most extracts. The methanol and ethanol extracts were the most active against M. smegmatis with an MIC of 25 mu g/mL. The hexane extract was the most active against Candida krusei with an MIC of 25 mu g/mL. None of the extracts significantly inhibited growth of Klebsiella pneumoniae and Staphylococcus aureus. Active extracts were selected for fractionation and isolation of pure compounds using gradient elution column chromatography. TLC analyses was carried out for pooling fractions of similar profiles. A total of 43 pools were obtained from 428 fractions. Pools 7 and 10 were selected for further isolation of single compounds. Four compounds, Pc4963r, Pc4962w, Pc6978p, and Pc6978o, were isolated. Evaluation of antimicrobial activities of Pc4963r, Pc4962w, and Pc6978p showed that the compounds were most active against C. krusei with MFC values ranging from 50 to 100 mu g/mL. Only Pc6978p was shown to be pure. Using spectroscopic analyses, the structure of Pc6978p was determined to be beta-sitosterol. The antifungal effects of beta-sitosterol were evaluated against C. krusei in vitro and on fabrics. Results showed that beta-sitosterol reduced the growth of C. krusei attached to Mendy fabric by 83%. Therefore, P. curatellifolia can be a source of lead compounds for prospective development of novel antimicrobial agents. Further work needs to be done to improve the antifungal activity of the isolated compound using quantitative structure-activity relationships.
Y1 - 2021
U6 - https://doi.org/10.1155/2021/8842629
SN - 2633-4682
SN - 2633-4690
PB - Hindawi
CY - London
ER -
TY - JOUR
A1 - Bekir, Marek
A1 - Jelken, Joachim
A1 - Jung, Se-Hyeong
A1 - Pich, Andrij
A1 - Pacholski, Claudia
A1 - Kopyshev, Alexey
A1 - Santer, Svetlana
T1 - Dual responsiveness of microgels induced by single light stimulus
JF - Applied physics letters
N2 - We report on the multiple response of microgels triggered by a single optical stimulus. Under irradiation, the volume of the microgels is reversibly switched by more than 20 times. The irradiation initiates two different processes: photo-isomerization of the photo-sensitive surfactant, which forms a complex with the anionic microgel, rendering it photo-responsive; and local heating due to a thermo-plasmonic effect within the structured gold layer on which the microgel is deposited. The photo-responsivity is related to the reversible accommodation/release of the photo-sensitive surfactant depending on its photo-isomerization state, while the thermo-sensitivity is intrinsically built in. We show that under exposure to green light, the thermo-plasmonic effect generates a local hot spot in the gold layer, resulting in the shrinkage of the microgel. This process competes with the simultaneous photo-induced swelling. Depending on the position of the laser spot, the spatiotemporal control of reversible particle shrinking/swelling with a predefined extent on a per-second base can be implemented.
Y1 - 2021
U6 - https://doi.org/10.1063/5.0036376
SN - 0003-6951
SN - 1077-3118
VL - 118
IS - 9
PB - American Institute of Physics
CY - Melville
ER -
TY - JOUR
A1 - Neffe, Axel T.
A1 - Löwenberg, Candy
A1 - Lendlein, Andreas
T1 - Hydrogel networks by aliphatic dithiol Michael addition to glycidylmethacrylated gelatin
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - Functionalization of gelatin with glycidylmethacrylate (GMA-gelatin) enables network formation employing the double bond, so that the reaction is orthogonal to the inherent functional groups in the biomacromolecule. Here, network formation by crosslinking of GMA-gelatin with hexane 1,6-dithiol or nonane 1,9-dithiol to tailor properties and enable a shape-memory effect is shown by H-1 NMR and FT-IR spectroscopy. Hydrogel swelling (460-1900 vol%) and mechanical properties (Young's modulus E = 59-512 kPa, elongation at break epsilon(b) = 44-127%) depended on the molecular composition of the networks and temperature. Increased crosslinker length, thiol:methacrylate molar ratio, and precursor concentrations led to denser networks. Change of properties with temperature suggested adoption of triple helices by gelatin chains, forming physical netpoints at lower temperatures (< 20 degrees C). However, the limited freedom of the gelatin chains to move allowed only a minimal extent of triple helices formation, as it became apparent from the related signal in wide-angle X-ray scattering and the thermal transition associated to triple helices in some networks by DSC. The presented strategy is likely transferable to other biomacromolecules, and the results suggest that too short crosslinkers may result in a significant amount of grafting rather than network formation.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00136-8
SN - 2059-8521
VL - 6
IS - 33
SP - 796
EP - 800
PB - Springer Nature Switzerland AG
CY - Cham
ER -
TY - JOUR
A1 - Lau, Skadi
A1 - Maier, Anna
A1 - Braune, Steffen
A1 - Gossen, Manfred
A1 - Lendlein, Andreas
T1 - Effect of endothelial culture medium composition on platelet responses to polymeric biomaterials
JF - International journal of molecular sciences
N2 - Near-physiological in vitro thrombogenicity test systems for the evaluation of blood-contacting endothelialized biomaterials requires co-cultivation with platelets (PLT). However, the addition of PLT has led to unphysiological endothelial cell (EC) detachment in such in vitro systems. A possible cause for this phenomenon may be PLT activation triggered by the applied endothelial cell medium, which typically consists of basal medium (BM) and nine different supplements. To verify this hypothesis, the influence of BM and its supplements was systematically analyzed regarding PLT responses. For this, human platelet rich plasma (PRP) was mixed with BM, BM containing one of nine supplements, or with BM containing all supplements together. PLT adherence analysis was carried out in six-channel slides with plasma-treated cyclic olefin copolymer (COC) and poly(tetrafluoro ethylene) (PTFE, as a positive control) substrates as part of the six-channel slides in the absence of EC and under static conditions. PLT activation and aggregation were analyzed using light transmission aggregometry and flow cytometry (CD62P). Medium supplements had no effect on PLT activation and aggregation. In contrast, supplements differentially affected PLT adherence, however, in a polymer- and donor-dependent manner. Thus, the use of standard endothelial growth medium (BM + all supplements) maintains functionality of PLT under EC compatible conditions without masking the differences of PLT adherence on different polymeric substrates. These findings are important prerequisites for the establishment of a near-physiological in vitro thrombogenicity test system assessing polymer-based cardiovascular implant materials in contact with EC and PLT.
KW - cyclic olefin copolymer
KW - poly(tetrafluoroethylene)
KW - endothelial cells
KW - platelets
KW - in vitro thrombogenicity testing
Y1 - 2021
U6 - https://doi.org/10.3390/ijms22137006
SN - 1422-0067
SN - 1661-6596
VL - 22
IS - 13
PB - Molecular Diversity Preservation International
CY - Basel
ER -
TY - JOUR
A1 - Schönemann, Eric
A1 - Koc, Julian
A1 - Karthäuser, Jana
A1 - Özcan, Onur
A1 - Schanzenbach, Dirk
A1 - Schardt, Lisa
A1 - Rosenhahn, Axel
A1 - Laschewsky, André
T1 - Sulfobetaine methacrylate polymers of unconventional polyzwitterion architecture and their antifouling properties
JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences
N2 - Combining high hydrophilicity with charge neutrality, polyzwitterions are intensely explored for their high biocompatibility and low-fouling properties. Recent reports indicated that in addition to charge neutrality, the zwitterion's segmental dipole orientation is an important factor for interacting with the environment. Accordingly, a series of polysulfobetaines with a novel architecture was designed, in which the cationic and anionic groups of the zwitterionic moiety are placed at equal distances from the backbone. They were investigated by in vitro biofouling assays, covering proteins of different charges and model marine organisms. All polyzwitterion coatings reduced the fouling effectively compared to model polymer surfaces of poly(butyl methacrylate), with a nearly equally good performance as the reference polybetaine poly(3-(N-(2-(methacryloyloxy)ethyl)-N,N-dimethylammonio)propanesulfonate). The specific fouling resistance depended on the detailed chemical structure of the polyzwitterions. Still, while clearly affecting the performance, the precise dipole orientation of the sulfobetaine group in the polyzwitterions seems overall to be only of secondary importance for their antifouling behavior.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.biomac.0c01705
SN - 1525-7797
SN - 1526-4602
VL - 22
IS - 4
SP - 1494
EP - 1508
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Ihlenburg, Ramona
A1 - Mai, Tobias
A1 - Thünemann, Andreas F.
A1 - Baerenwald, Ruth
A1 - Saalwächter, Kay
A1 - Koetz, Joachim
A1 - Taubert, Andreas
T1 - Sulfobetaine hydrogels with a complex multilength-scale hierarchical structure
JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2 - Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker N,N,N',N'-tetramethyl-N,N'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers.
KW - Defects
KW - Hydrogels
KW - Nuclear magnetic resonance spectroscopy
KW - Scattering
KW - X-ray scattering
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jpcb.0c10601
SN - 1520-6106
SN - 1520-5207
VL - 125
IS - 13
SP - 3398
EP - 3408
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Zhang, Pengfei
A1 - Rešetič, Andraž
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Multifunctionality in polymer networks by dynamic of coordination bonds
JF - Macromolecular chemistry and physics
N2 - The need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self-healing capability, fluorescence stimuli-responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)-phosphine coordination bonds, which in a polymer network act with their dynamic and non-covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium-phosphine ions across and through contacting areas of the material provide for reshaping and self-healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material-sensing capabilities.
KW - assembly capabilities
KW - fluorescence stimuli‐ responsivity
KW - multiple functions
KW - reshaping abilities
KW - rhodium(I)– phosphine
KW - coordination bonds
KW - solvent resistance
Y1 - 2021
U6 - https://doi.org/10.1002/macp.202000394
SN - 1521-3935
VL - 222
IS - 3
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Machatschek, Rainhard Gabriel
A1 - Heuchel, Matthias
A1 - Lendlein, Andreas
T1 - Hydrolytic stability of polyetherimide investigated in ultrathin films
JF - Journal of materials research : JMR / Materials Research Society
N2 - Increasing the surface hydrophilicity of polyetherimide (PEI) through partial hydrolysis of the imide groups while maintaining the length of the main-chain was explored for adjusting its function in biomedical and membrane applications. The outcome of the polymer analogous reaction, i.e., the degree of ring opening and chain cleavage, is difficult to address in bulk and microstructured systems, as these changes only occur at the interface. Here, the reaction was studied at the air-water interface using the Langmuir technique, assisted by atomic force microscopy and vibrational spectroscopy. Slow PEI hydrolysis sets in at pH > 12. At pH = 14, the ring opening is nearly instantaneous. Reduction of the layer viscosity with time at pH = 14 suggested moderate chain cleavage. No hydrolysis was observed at pH = 1. Hydrolyzed PEI films had a much more cohesive structure, suggesting that the nanoporous morphology of PEI can be tuned via hydrolysis.
KW - 2D materials
KW - Membrane
KW - Polymer
KW - Water
KW - Nanostructure
Y1 - 2021
U6 - https://doi.org/10.1557/s43578-021-00267-6
SN - 0884-2914
SN - 2044-5326
VL - 36
IS - 14
SP - 2987
EP - 2994
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Machatschek, Rainhard Gabriel
A1 - Heuchel, Matthias
A1 - Lendlein, Andreas
T1 - Thin-layer studies on surface functionalization of polyetherimide
BT - hydrolysis versus amidation
JF - Journal of materials research : JMR / Materials Research Society
N2 - Among the high-performance and engineering polymers, polyimides and the closely related polyetherimide (PEI) stand out by their capability to react with nucleophiles under relatively mild conditions. By targeting the phthalimide groups in the chain backbone, post-functionalization offers a pathway to adjust surface properties such as hydrophilicity, solvent resistance, and porosity. Here, we use ultrathin PEI films on a Langmuir trough as a model system to investigate the surface functionalization with ethylene diamine and tetrakis(4-aminophenyl)porphyrin as multivalent nucleophiles. By means of AFM, Raman spectroscopy, and interfacial rheology, we show that hydrolysis enhances the chemical and mechanical stability of ultrathin films and allows for the formation of EDC/NHS-activated esters. Direct amidation of PEI was achieved in the presence of a Lewis acid catalyst, resulting in free amine groups rather than cross-linking. When comparing amidation with hydrolysis, we find a greater influence of the latter on material properties.
KW - Membrane
KW - Nanostructure
KW - Polymer
KW - Raman spectroscopy
KW - Scanning probe microscopy (SPM)
KW - Surface reaction
KW - Thin film
Y1 - 2021
U6 - https://doi.org/10.1557/s43578-021-00339-7
SN - 0884-2914
SN - 2044-5326
VL - 37
IS - 1
SP - 67
EP - 76
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Buyinza, Daniel
A1 - Derese, Solomon
A1 - Ndakala, Albert
A1 - Heydenreich, Matthias
A1 - Yenesew, Abiy
A1 - Koch, Andreas
A1 - Oriko, Richard
T1 - A coumestan and a coumaronochromone from Millettia lasiantha
JF - Biochemical systematics and ecology
N2 - The manuscript describes the phytochemical investigation of the roots, leaves and stem bark of Millettia lasiantha resulting in the isolation of twelve compounds including two new isomeric isoflavones lascoumestan and las-coumaronochromone. The structures of the new compounds were determined using different spectroscopic techniques.
KW - Millettia lasiantha
KW - Leguminosae
KW - Coumestan
KW - Coumaronochromone
Y1 - 2021
U6 - https://doi.org/10.1016/j.bse.2021.104277
SN - 0305-1978
SN - 1873-2925
VL - 97
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Gharabekyan, Hrant H.
A1 - Koetz, Joachim
A1 - Poghosyan, Armen H.
T1 - A protonated L-cysteine adsorption on gold surface
BT - a molecular dynamics study
JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2 - The adsorption of protonated L-cysteine onto Au(111) surface was studied via molecular dynamics method. The detailed examination of trajectories reveals that a couple of picoseconds need to be strongly adsorbed at the gold surface via L-cysteine's sulfur and oxygen atoms. The average distances of L-cysteine's adsorbed sulfur and oxygen from gold plane are-2.7 angstrom and-3.2 angstrom, correspondingly. We found that the adsorption of L-cysteine takes place preferentially at bridge site with possibility of-82%. Discussing the conformation features of protonated L-cysteine, we consider that the most stable conformation of protonated L-cysteine is "reverse boat" position, where sulfur and oxygen pointed down to the gold surface, while the amino group is far from the gold surface.
KW - MD simulations
KW - gold surface
KW - GOIP
KW - l-cysteine
KW - adsorption
KW - protonation
Y1 - 2021
U6 - https://doi.org/10.1016/j.colsurfa.2021.127452
SN - 0927-7757
SN - 1873-4359
VL - 629
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Bouakline, Foudhil
A1 - Saalfrank, Peter
T1 - Seemingly asymmetric atom-localized electronic densities following laser-dissociation of homonuclear diatomics
JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2 - Recent experiments on laser-dissociation of aligned homonuclear diatomic molecules show an asymmetric forward-backward (spatial) electron-localization along the laser polarization axis. Most theoretical models attribute this asymmetry to interference effects between gerade and ungerade vibronic states. Presumably due to alignment, these models neglect molecular rotations and hence infer an asymmetric (post-dissociation) charge distribution over the two identical nuclei. In this paper, we question the equivalence that is made between spatial electron-localization, observed in experiments, and atomic electron-localization, alluded by these theoretical models. We show that (seeming) agreement between these models and experiments is due to an unfortunate omission of nuclear permutation symmetry, i.e., quantum statistics. Enforcement of the latter requires mandatory inclusion of the molecular rotational degree of freedom, even for perfectly aligned molecules. Unlike previous interpretations, we ascribe spatial electron-localization to the laser creation of a rovibronic wavepacket that involves field-free molecular eigenstates with opposite space-inversion symmetry i.e., even and odd parity. Space-inversion symmetry breaking would then lead to an asymmetric distribution of the (space-fixed) electronic density over the forward and backward hemisphere. However, owing to the simultaneous coexistence of two indistinguishable molecular orientational isomers, our analytical and computational results show that the post-dissociation electronic density along a specified space-fixed axis is equally shared between the two identical nuclei-a result that is in perfect accordance with the principle of the indistinguishability of identical particles. Published under an exclusive license by AIP Publishing.
Y1 - 2021
U6 - https://doi.org/10.1063/5.0049710
SN - 0021-9606
SN - 1089-7690
VL - 154
IS - 23
PB - American Institute of Physics
CY - Melville
ER -
TY - JOUR
A1 - Qiu, Liang
A1 - Zhang, Haoran
A1 - Bick, Thomas
A1 - Martin, Johannes
A1 - Wendler, Petra
A1 - Böker, Alexander
A1 - Glebe, Ulrich
A1 - Xing, Chengfen
T1 - Construction of highly ordered glyco-inside nano-assemblies through RAFT dispersion polymerization of galactose-decorated monomer
JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2 - Glyco-assemblies derived from amphiphilic sugar-decorated block copolymers (ASBCs) have emerged prominently due to their wide application, for example, in biomedicine and as drug carriers. However, to efficiently construct these glyco-assemblies is still a challenge. Herein, we report an efficient technology for the synthesis of glyco-inside nano-assemblies by utilizing RAFT polymerization of a galactose-decorated methacrylate for polymerization-induced self-assembly (PISA). Using this approach, a series of highly ordered glyco-inside nano-assemblies containing intermediate morphologies were fabricated by adjusting the length of the hydrophobic glycoblock and the polymerization solids content. A specific morphology of complex vesicles was captured during the PISA process and the formation mechanism is explained by the morphology of its precursor and intermediate. Thus, this method establishes a powerful route to fabricate glyco-assemblies with tunable morphologies and variable sizes, which is significant to enable the large-scale fabrication and wide application of glyco-assemblies.
KW - galactose-decorated monomer
KW - glyco-inside nano-assemblies
KW - morphology
KW - evolution
KW - PISA
KW - RAFT dispersion polymerization
Y1 - 2021
U6 - https://doi.org/10.1002/anie.202015692
SN - 1433-7851
SN - 1521-3773
VL - 60
IS - 20
SP - 11098
EP - 11103
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Sperlich, Eric
A1 - Köckerling, Martin
T1 - Cluster salts [Nb6Cl12(HIm)(6)]A(n) (with HIm=1H-imidazole and A=Mineral Acid Anion, n=1 or 2) made in and with Bronsted-basic ionic liquids and liquid mixtures
JF - ChemistryOpen
N2 - Four new hexanuclear niobium cluster compounds of the general formula [Nb6Cl12(HIm)(6)](A)(n) . x(solvent molecule) (HIm=1H-imidazole, A=mineral acid anion, Cl- (n=2) (1), (SO4)(2-) (n=1) (2), (CrO4)(2-) (n=1) (3), and (HAsO4)(2-) (n=1) (4)) were prepared. Their synthesis can be done in basic ionic liquids, which form on the addition of a mineral acid, which also delivers the counter anion for the final cluster compound, to an excess of the 1H-imidazole. Some addition of an auxiliary solvent, like methanol, improves the speed of crystallisation. The cluster unit comprises a hexanuclear Nb-6 unit of octahedral shape with the edges bridged by Cl atoms and the exo sites being occupied by N-bonded 1H-imidazole ligands. The cluster cation carries sixteen cluster-based electrons. Between the NH groups of the ligands of the cluster unit, the anions and the co-crystallised water (1), or 1H-imidazole and methanol molecules (2, 3, and 4) a network of hydrogen bonds exists.
KW - cluster
KW - ionic liquid
KW - structure elucidation
KW - heterocyclic ligand
KW - Niobium
Y1 - 2021
U6 - https://doi.org/10.1002/open.202000266
SN - 2191-1363
VL - 10
IS - 2
SP - 248
EP - 254
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Akarsu, Pinar
A1 - Grobe, Richard
A1 - Nowaczyk, Julius
A1 - Hartlieb, Matthias
A1 - Reinicke, Stefan
A1 - Böker, Alexander
A1 - Sperling, Marcel
A1 - Reifarth, Martin
T1 - Solid-phase microcontact printing for precise patterning of rough surfaces
BT - using polymer-tethered elastomeric stamps for the transfer of reactive silanes
JF - ACS applied polymer materials
N2 - We present a microcontact printing (mu CP) routine suitable to introduce defined (sub-) microscale patterns on surface substrates exhibiting a high capillary activity and receptive to a silane-based chemistry. This is achieved by transferring functional trivalent alkoxysilanes, such as (3-aminopropyl)-triethoxysilane (APTES) as a low-molecular weight ink via reversible covalent attachment to polymer brushes grafted from elastomeric polydimethylsiloxane (PDMS) stamps. The brushes consist of poly{N-[tris(hydroxymethyl)-methyl]acrylamide} (PTrisAAm) synthesized by reversible addition-fragmentation chain-transfer (RAFT)-polymerization and used for immobilization of the alkoxysilane-based ink by substituting the alkoxy moieties with polymer-bound hydroxyl groups. Upon physical contact of the silane-carrying polymers with surfaces, the conjugated silane transfers to the substrate, thus completely suppressing ink-flow and, in turn, maximizing printing accuracy even for otherwise not addressable substrate topographies. We provide a concisely conducted investigation on polymer brush formation using atomic force microscopy (AFM) and ellipsometry as well as ink immobilization utilizing two-dimensional proton nuclear Overhauser enhancement spectroscopy (H-1-H-1-NOESY-NMR). We analyze the mu CP process by printing onto Si-wafers and show how even distinctively rough surfaces can be addressed, which otherwise represent particularly challenging substrates.
KW - microcontact printing
KW - capillary-active substrates
KW - silane chemistry
KW - PDMS surface grafting
KW - surface patterning
KW - shuttled RAFT-polymerization
Y1 - 2021
U6 - https://doi.org/10.1021/acsapm.1c00024
SN - 2637-6105
VL - 3
IS - 5
SP - 2420
EP - 2431
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Riemer, Nastja
A1 - Riemer, Martin
A1 - Krüger, Mandy
A1 - Clarkson, Guy J.
A1 - Shipman, Michael
A1 - Schmidt, Bernd
T1 - Synthesis of arylidene-beta-lactams via exo-selective Matsuda-Heck arylation of methylene-beta-lactams
JF - The journal of organic chemistry : JOC
N2 - exo-Methylene-beta-lactams were synthesized in two steps from commercially available 3-bromo-2-(bromomethyl)-propionic acid and reacted with arene diazonium salts in a Heck-type arylation in the presence of catalytic amounts of Pd(OAc)(2) under ligand-free conditions. The products, arylidene-beta-lactams, were obtained in high yields as single isomers. The beta-hydride elimination step of the Pd-catalyzed coupling reaction proceeds with high exo-regioselectivity and E-stereoselectivity. With aryl iodides, triflates, or bromides, the coupling products were isolated only in low yields, due to extensive decomposition of the starting material at elevated temperatures. This underlines that arene diazonium salts can be superior arylating reagents in Heck-type reactions and yield coupling products in synthetically useful yields and selectivities when conventional conditions fail.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.joc.1c00638
SN - 0022-3263
SN - 1520-6904
VL - 86
IS - 13
SP - 8786
EP - 8796
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Balischewski, Christian
A1 - Choi, Hyung-Seok
A1 - Behrens, Karsten
A1 - Beqiraj, Alkit
A1 - Körzdörfer, Thomas
A1 - Gessner, Andre
A1 - Wedel, Armin
A1 - Taubert, Andreas
T1 - Metal sulfide nanoparticle synthesis with ionic liquids state of the art and future perspectives
JF - ChemistryOpen
N2 - Metal sulfides are among the most promising materials for a wide variety of technologically relevant applications ranging from energy to environment and beyond. Incidentally, ionic liquids (ILs) have been among the top research subjects for the same applications and also for inorganic materials synthesis. As a result, the exploitation of the peculiar properties of ILs for metal sulfide synthesis could provide attractive new avenues for the generation of new, highly specific metal sulfides for numerous applications. This article therefore describes current developments in metal sulfide nano-particle synthesis as exemplified by a number of highlight examples. Moreover, the article demonstrates how ILs have been used in metal sulfide synthesis and discusses the benefits of using ILs over more traditional approaches. Finally, the article demonstrates some technological challenges and how ILs could be used to further advance the production and specific property engineering of metal sulfide nanomaterials, again based on a number of selected examples.
KW - Ionic liquids
KW - ionic liquid crystals
KW - ionic liquid precursors
KW - metal
KW - sulfides
KW - catalysis
KW - electrochemistry
KW - energy materials
KW - LED
KW - solar
KW - cells
Y1 - 2021
U6 - https://doi.org/10.1002/open.202000357
SN - 2191-1363
VL - 10
IS - 2
SP - 272
EP - 295
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Quan, Ting
A1 - Haerk, Eneli
A1 - Xu, Yaolin
A1 - Ahmet, Ibbi
A1 - Höhn, Christian
A1 - Mei, Shilin
A1 - Lu, Yan
T1 - Unveiling the formation of solid electrolyte interphase and its temperature dependence in "Water-in-Salt" supercapacitors
JF - ACS applied materials & interfaces
N2 - "Water-in-salt" (WIS) electrolytes have emerged as an excellent superconcentrated ionic medium for high-power energy storage systems such as supercapacitors due to their extended working potential compared to the conventional dilute aqueous electrolyte. In this work, we have investigated the performance of WIS supercapacitors using hollow carbon nanoplates as electrodes and compared it to that based on the conventional "salt-in-water" electrolytes. Moreover, the potentiostatic electrochemical impedance spectroscopy has been employed to provide an insightful look into the charge transport properties, which also, for the first time, reveals the formation of a solid-electrolyte interphase (SEI and their temperature-dependent impedance for charge transfer and adsorption. Furthermore, the effect of temperature on the electrochemical performance of the WIS supercapacitors in the temperature range from 15 to 60 degrees C has been studied, which presents a gravimetric capacitance of 128 F g(-1) and a volumetric capacitance of 197.12 F cm(-3) at 55 degrees C compared to 87.5 F g(-1) and 134.75 F cm(-3) at 15 degrees C. The in-depth understanding about the formation of SEI layer and the electrochemical performance at different temperatures for WIS supercapacitors will assist the efforts toward designing better aqueous electrolytes for supercapacitors.
KW - "water-in-salt"
KW - supercapacitor
KW - solid electrolyte interphase
KW - electrochemical impedance spectroscopy
KW - temperature effect
Y1 - 2021
U6 - https://doi.org/10.1021/acsami.0c19506
SN - 1944-8244
SN - 1944-8252
VL - 13
IS - 3
SP - 3979
EP - 3990
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Behl, Marc
A1 - Balk, Maria
A1 - Lützow, Karola
A1 - Lendlein, Andreas
T1 - Impact of block sequence on the phase morphology of multiblock copolymers obtained by high-throughput robotic synthesis
JF - European polymer journal : EPJ
N2 - The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. We hypothesized that a strictly alternating sequence should favour phase segregation and in this way the elastic properties. A library of well-defined MBCs composed of two different hydrophobic, semi-crystalline blocks providing domains with well-separated melting temperatures (T(m)s) were synthesized from the same type of precursor building blocks as strictly alternating (MBCsalt) or random (MBCsran) MBCs and compared. Three different series of MBCsalt or MBCsran were synthesized by high-throughput synthesis by coupling oligo(e-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification in which the molar ratio of the reaction partners was slightly adjusted. Maximum of weight average molecular weight (M-w) were 65,000 g center dot mol(-1), 165,000 g center dot mol(-1), and 168,000 g center dot mol(-1) for MBCsalt and 80,500 g center dot mol(-1), 100,000 g center dot mol(-1), and 147,600 g center dot mol(-1) for MBCsran. When Mw increased, a decrease of both Tms associated to the melting of the OCL and OTHF domains was observed for all MBCs. T-m (OTHF) of MBCsran was always higher than Tm (OTHF) of MBCsalt, which was attributed to a better phase segregation. In addition, the elongation at break of MBCsalt was almost half as high when compared to MBCsran. In this way this study elucidates role of the block length and sequence structure in MBCs and enables a quantitative discussion of the structure-function relationship when two semi-crystalline block segments are utilized for the design of block copolymers.
KW - Multiblock copolymers
KW - Sequence structure
KW - Phase morphology
KW - Polymer
KW - library
KW - Robotic synthesis
KW - High-throughput
Y1 - 2021
U6 - https://doi.org/10.1016/j.eurpolymj.2020.110207
SN - 0014-3057
SN - 1873-1945
VL - 143
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Schlappa, Stephanie
A1 - Brenker, Lee Josephine
A1 - Bressel, Lena
A1 - Hass, Roland
A1 - Münzberg, Marvin
T1 - Process characterization of polyvinyl acetate emulsions applying inline photon density wave spectroscopy at high solid contents
JF - Polymers / Molecular Diversity Preservation International
N2 - The high solids semicontinuous emulsion polymerization of polyvinyl acetate using poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated by optical spectroscopy. The suitability of Photon Density Wave (PDW) spectroscopy as inline Process Analytical Technology (PAT) for emulsion polymerization processes at high solid contents (>40% (w/w)) is studied and evaluated. Inline data on absorption and scattering in the dispersion is obtained in real-time. The radical polymerization of vinyl acetate to polyvinyl acetate using ascorbic acid and sodium persulfate as redox initiator system and poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated. Starved-feed radical emulsion polymerization yielded particle sizes in the nanometer size regime. PDW spectroscopy is used to monitor the progress of polymerization by studying the absorption and scattering properties during the synthesis of dispersions with increasing monomer amount and correspondingly decreasing feed rate of protective colloid. Results are compared to particle sizes determined with offline dynamic light scattering (DLS) and static light scattering (SLS) during the synthesis.
KW - photon density wave spectroscopy
KW - multiple light scattering
KW - emulsion
KW - polymerization
KW - process analytical technology
KW - polyvinyl acetate
Y1 - 2021
U6 - https://doi.org/10.3390/polym13040669
SN - 2073-4360
VL - 13
IS - 4
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Harmanli, İpek
A1 - Tarakina, Nadezda
A1 - Antonietti, Markus
A1 - Oschatz, Martin
T1 - "Giant" nitrogen uptake in ionic liquids confined in carbon pores
JF - Journal of the American Chemical Society
N2 - Ionic liquids are well known for their high gas absorption capacity. It is shown that this is not a solvent constant, but can be enhanced by another factor of 10 by pore confinement, here of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EmimOAc) in the pores of carbon materials. A matrix of four different carbon compounds with micro- and mesopores as well as with and without nitrogen doping is utilized to investigate the influence of the carbons structure on the nitrogen uptake in the pore-confined EmimOAc. In general, the absorption is most improved for IL in micropores and in nitrogen-doped carbon. This effect is so large that it is already seen in TGA and DSC experiments. Due to the low vapor pressure of the IL, standard volumetric sorption experiments can be used to quantify details of this effect. It is reasoned that it is the change of the molecular arrangement of the ions in the restricted space of the pores that creates additional free volume to host molecular nitrogen.
Y1 - 2021
U6 - https://doi.org/10.1021/jacs.1c00783
SN - 0002-7863
SN - 1520-5126
VL - 143
IS - 25
SP - 9377
EP - 9384
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Frieß, Fabian
A1 - Lendlein, Andreas
A1 - Wischke, Christian
T1 - Switching microobjects from low to high aspect ratios using a shape-memory effect
JF - Soft matter
N2 - Spherical particles from shape-memory polymers (SMP) can be stretched to ellipsoids with high aspect ratio (AR) and temporarily stabilized. They can switch back to low AR upon thermal stimulation. Here, the creation of an alternative shape-switching capability of particles from low to high AR is introduced, where a SMP matrix from polyvinyl alcohol (PVA) is used to create crosslinked high AR particles and to program the embedded micrometer-sized particles from a second SMP (oligo(epsilon-caprolactone) micronetworks, MN) with a low switching temperature T-sw. This programming proceeds through shape-recovery of the PVA matrix, from which the MN are harvested by PVA matrix dissolution. The use of a dissolvable SMP matrix may be a general strategy to efficiently create systems with complex moving capabilities.
Y1 - 2021
U6 - https://doi.org/10.1039/d1sm00947h
SN - 1744-6848
VL - 17
IS - 41
SP - 9326
EP - 9331
PB - Royal Society of Chemistry
CY - London
ER -
TY - JOUR
A1 - Lau, Skadi
A1 - Gossen, Manfred
A1 - Lendlein, Andreas
T1 - Designing cardiovascular implants taking in view the endothelial basement membrane
JF - International journal of molecular sciences
N2 - Insufficient endothelialization of cardiovascular grafts is a major hurdle in vascular surgery and regenerative medicine, bearing a risk for early graft thrombosis. Neither of the numerous strategies pursued to solve these problems were conclusive. Endothelialization is regulated by the endothelial basement membrane (EBM), a highly specialized part of the vascular extracellular matrix. Thus, a detailed understanding of the structure-function interrelations of the EBM components is fundamental for designing biomimetic materials aiming to mimic EBM functions. In this review, a detailed description of the structure and functions of the EBM are provided, including the luminal and abluminal interactions with adjacent cell types, such as vascular smooth muscle cells. Moreover, in vivo as well as in vitro strategies to build or renew EBM are summarized and critically discussed. The spectrum of methods includes vessel decellularization and implant biofunctionalization strategies as well as tissue engineering-based approaches and bioprinting. Finally, the limitations of these methods are highlighted, and future directions are suggested to help improve future design strategies for EBM-inspired materials in the cardiovascular field.
KW - endothelial cells
KW - bioinstructive implants
KW - vascular grafts
KW - tissue
KW - engineering
KW - bioprinting
KW - bioinspired materials
KW - biological membrane
KW - endothelial basement membrane
KW - biomaterial
Y1 - 2021
U6 - https://doi.org/10.3390/ijms222313120
SN - 1422-0067
VL - 22
IS - 23
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Kogikoski Junior, Sergio
A1 - Dutta, Anushree
A1 - Bald, Ilko
T1 - Spatial separation of plasmonic hot-electron generation and a hydrodehalogenation reaction center using a DNA wire
JF - ACS nano
N2 - Using hot charge carriers far from a plasmonic nanoparticle surface is very attractive for many applications in catalysis and nanomedicine and will lead to a better understanding of plasmon-induced processes, such as hot-charge-carrier- or heat-driven chemical reactions. Herein we show that DNA is able to transfer hot electrons generated by a silver nanoparticle over several nanometers to drive a chemical reaction in a molecule nonadsorbed on the surface. For this we use 8-bromo-adenosine introduced in different positions within a double-stranded DNA oligonucleotide. The DNA is also used to assemble the nanoparticles into nanoparticles ensembles enabling the use of surface-enhanced Raman scattering to track the decomposition reaction. To prove the DNA-mediated transfer, the probe molecule was insulated from the source of charge carriers, which hindered the reaction. The results indicate that DNA can be used to study the transfer of hot electrons and the mechanisms of advanced plasmonic catalysts.
KW - plasmonics
KW - DNA nanotechnology
KW - hot electrons
KW - charge transfer
KW - SERS
KW - superlattices
Y1 - 2021
U6 - https://doi.org/10.1021/acsnano.1c09176
SN - 1936-0851
SN - 1936-086X
VL - 15
IS - 12
SP - 20562
EP - 20573
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Fudickar, Werner
A1 - Bauch, Marcel
A1 - Ihmels, Heiko
A1 - Linker, Torsten
T1 - DNA-triggered enhancement of singlet oxygen production by pyridinium alkynylanthracenes
JF - Chemistry - a European journal
N2 - There is an ongoing interest in O-1(2) sensitizers, whose activity is selectively controlled by their interaction with DNA. To this end, we synthesized three isomeric pyridinium alkynylanthracenes 2 o-p and a water-soluble trapping reagent for O-1(2). In water and in the absence of DNA, these dyes show a poor efficiency to sensitize the photooxygenation of the trapping reagent as they decompose due to electron transfer processes. In contrast, in the presence of DNA O-1(2) is generated from the excited DNA-bound ligand. The interactions of 2 o-p with DNA were investigated by thermal DNA melting studies, UV/vis and fluorescence spectroscopy, and linear and circular dichroism spectroscopy. Our studies revealed an intercalative binding with an orientation of the long pyridyl-alkynyl axis parallel to the main axis of the DNA base pairs. In the presence of poly(dA : dT), all three isomers show an enhanced formation of singlet oxygen, as indicated by the reaction of the latter with the trapping reagent. With green light irradiation of isomer 2 o in poly(dA : dT), the conversion rate of the trapping reagent is enhanced by a factor >10. The formation of O-1(2) was confirmed by control experiments under anaerobic conditions, in deuterated solvents, or by addition of O-1(2) quenchers. When bound to poly(dG : dC), the opposite effect was observed only for isomers 2 o and 2 m, namely the trapping reagent reacted significantly slower. Overall, we showed that pyridinium alkynylanthracenes are very useful intercalators, that exhibit an enhanced photochemical O-1(2) generation in the DNA-bound state.
KW - Anthracene
KW - DNA
KW - intercalations
KW - photochemistry
KW - singlet oxygen
Y1 - 2021
U6 - https://doi.org/10.1002/chem.202101918
SN - 1521-3765
VL - 27
IS - 54
SP - 13591
EP - 13604
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Balk, Maria
A1 - Behl, Marc
A1 - Nöchel, Ulrich
A1 - Lendlein, Andreas
T1 - Enzymatically triggered Jack-in-the-box-like hydrogels
JF - ACS applied materials & interfaces / American Chemical Society
N2 - Enzymes can support the synthesis or degradation of biomacromolecules in natural processes. Here, we demonstrate that enzymes can induce a macroscopic-directed movement of microstructured hydrogels following a mechanism that we call a "Jack-in-the-box" effect. The material's design is based on the formation of internal stresses induced by a deformation load on an architectured microscale, which are kinetically frozen by the generation of polyester locking domains, similar to a Jack-in-thebox toy (i.e., a compressed spring stabilized by a closed box lid). To induce the controlled macroscopic movement, the locking domains are equipped with enzyme-specific cleavable bonds (i.e., a box with a lock and key system). As a result of enzymatic reaction, a transformed shape is achieved by the release of internal stresses. There is an increase in entropy in combination with a swelling-supported stretching of polymer chains within the microarchitectured hydrogel (i.e., the encased clown pops-up with a pre-stressed movement when the box is unlocked). This utilization of an enzyme as a physiological stimulus may offer new approaches to create interactive and enzyme-specific materials for different applications such as an optical indicator of the enzyme's presence or actuators and sensors in biotechnology and in fermentation processes.
KW - enzyme
KW - hydrogels
KW - stimuli-sensitive materials
KW - shape change
KW - poly(e-caprolactone)
KW - switch
KW - microporous
Y1 - 2021
U6 - https://doi.org/10.1021/acsami.1c00466
SN - 1944-8244
SN - 1944-8252
VL - 13
IS - 7
SP - 8095
EP - 8101
PB - American Chemical Society
CY - Washington, DC
ER -
TY - JOUR
A1 - Oloya, Benson
A1 - Namukobe, Jane
A1 - Heydenreich, Matthias
A1 - Ssengooba, Willy
A1 - Schmidt, Bernd
A1 - Byamukama, Robert
T1 - Antimycobacterial activity of the extract and isolated compounds from the stem bark of Zanthoxylum leprieurii Guill. and Perr.
JF - Natural product communications : an international journal for communications and reviews
N2 - Zanthoxylum leprieurii Guill. and Perr. (Rutaceae) stem bark is used locally in Uganda for treating tuberculosis (TB) and cough-related infections. Lupeol (1), sesamin (2), trans-fagaramide (3), arnottianamide (4), (S)-marmesinin (5), and hesperidin (6) were isolated from the chloroform/methanol (1:1) extract of Z. leprieurii stem bark. Their structures were elucidated using spectroscopic techniques and by comparison with literature data. Furthermore, the extract and isolated compounds were subjected to antimycobacterial activity. The extract exhibited moderate activity against the susceptible (H(37)Rv) TB strain, but weak activity against the multidrug resistant (MDR)-TB strain with minimum inhibitory concentrations (MICs) of 586.0 and 1172.0 mu g/mL, respectively. Compound 3 (trans-fagaramide) showed significant antimycobacterial activity against the susceptible (H(37)Rv) TB strain (MIC 6 mu g/mL), but moderate activity against the MDR-TB strain (MIC 12.2 mu g/mL). Compounds 2, 5, 6, and 1 showed moderate activities against the susceptible (H(37)Rv) strain (MIC 12.2-98.0 mu g/mL) and moderate to weak activities against the MDR-TB strain (MIC 24.4-195.0 mu g/mL). This study reports for the first time the isolation of compounds 1 to 6 from the stem bark of Z leprieurii. trans-Fagaramide (3) may present a vital template in pursuit of novel and highly effective TB drugs.
KW - tuberculosis
KW - Zanthoxylum leprieurii
KW - antimycobacterial activity
KW - trans-fagaramide
KW - alkaloid
Y1 - 2021
U6 - https://doi.org/10.1177/1934578X211035851
SN - 1934-578X
SN - 1555-9475
VL - 16
IS - 8
PB - Sage Publ.
CY - Thousand Oaks
ER -
TY - JOUR
A1 - Folikumah, Makafui Yao
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Thiol-Thioester exchange reactions in precursors enable pH-triggered hydrogel formation
JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences
N2 - Bio-interactive hydrogel formation in situ requires sensory capabilities toward physiologically relevant stimuli. Here, we report on pH-controlled in situ hydrogel formation relying on latent cross-linkers, which transform from pH sensors to reactive molecules. In particular, thiopeptolide/thio-depsipeptides were capable of pH-sensitive thiol-thioester exchange reactions to yield a,co-dithiols, which react with maleimide-functionalized multi-arm polyethylene glycol to polymer networks. Their water solubility and diffusibility qualify thiol/thioester-containing peptide mimetics as sensory precursors to drive in situ localized hydrogel formation with potential applications in tissue regeneration such as treatment of inflamed tissues of the urinary tract.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.biomac.0c01690
SN - 1525-7797
SN - 1526-4602
VL - 22
IS - 5
SP - 1875
EP - 1884
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Xie, Dongjiu
A1 - Mei, Shilin
A1 - Xu, Yaolin
A1 - Quan, Ting
A1 - Haerk, Eneli
A1 - Kochovski, Zdravko
A1 - Lu, Yan
T1 - Efficient sulfur host based on yolk-shell iron oxide/sulfide-carbon nanospindles for lithium-sulfur batteries
JF - ChemSusChem : chemistry, sustainability, energy, materials
N2 - Numerous nanostructured materials have been reported as efficient sulfur hosts to suppress the problematic "shuttling" of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. However, direct comparison of these materials in their efficiency of suppressing LiPSs shuttling is challenging, owing to the structural and morphological differences between individual materials. This study introduces a simple route to synthesize a series of sulfur host materials with the same yolk-shell nanospindle morphology but tunable compositions (Fe3O4, FeS, or FeS2), which allows for a systematic investigation into the specific effect of chemical composition on the electrochemical performances of Li-S batteries. Among them, the S/FeS2-C electrode exhibits the best performance and delivers an initial capacity of 877.6 mAh g(-1) at 0.5 C with a retention ratio of 86.7 % after 350 cycles. This approach can also be extended to the optimization of materials for other functionalities and applications.
KW - batteries
KW - electrode materials
KW - lithium sulfides
KW - yolk-shell
KW - nanostructures
Y1 - 2021
U6 - https://doi.org/10.1002/cssc.202002731
SN - 1864-5631
SN - 1864-564X
VL - 14
IS - 5
SP - 1404
EP - 1413
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Otter, Dirk
A1 - Mondal, Suvendu Sekhar
A1 - Alrefai, Anas
A1 - Krätz, Lorenz
A1 - Holdt, Hans-Jürgen
A1 - Bart, Hans-Jörg
T1 - Characterization of an isostructural MOF series of Imidazolate Frameworks Potsdam by means of sorption experiments with water vapor
JF - Nanomaterials
N2 - Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs) connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The isotherm shapes were analyzed in order to gain insight into material properties and compared to sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water vapor sorption measurements are strongly influenced by the pore size distribution while having a distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and -8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and -5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice of the used linker substituents and transition metals employed in the framework has a tremendous effect on the material properties and functionality. The water uptake capacities of the examined IFPs are ranging 0.48 mmol g(-1) (IFP-4) to 6.99 mmol g(-1) (IFP-5) and comparable to those documented for ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8.
KW - material characterization
KW - water vapor
KW - adsorption
KW - hysteresis
KW - Imidazolate Frameworks Potsdam
Y1 - 2021
U6 - https://doi.org/10.3390/nano11061400
SN - 2079-4991
VL - 11
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Friess, Fabian
A1 - Lendlein, Andreas
A1 - Wischke, Christian
T1 - Size control of shape switchable micronetworks by fast two-step microfluidic templating
JF - Journal of materials research
N2 - Shape-memory polymer micronetworks (MN) are micrometer-sized objects that can switch their outer shape upon external command.This study aims to scale MN sizes to the low micrometer range at very narrow size distributions. In a two-step microfluidic strategy, the specific design of coaxial class capillary devices allowed stabilizing the thread of the dispersed phase to efficiently produce precursor particles in the tip-streaming regime at rates up to similar to 170 kHz and final sizes down to 4 mu m. In a subsequent melt-based microfluidic photocrosslinking of the methacrylate-functionalized oligo(epsilon-caprolactone) precursor material, MN could be produced without particle aggregation. A comprehensive analysis of MN properties illustrated successful crosslinking, semi-crystalline morphology, and a shape-switching functionality for all investigated MN sizes (4, 6, 9, 12, 22 mu m). Such functional micronetworks tailored to and below the dimension of cells can enable future applications in technology and medicine like controlling cell interaction.
Y1 - 2021
U6 - https://doi.org/10.1557/s43578-021-00295-2
SN - 0884-2914
SN - 2044-5326
VL - 36
IS - 16
SP - 3248
EP - 3257
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Sperlich, Eric
A1 - Köckerling, Martin
T1 - [Nb6Cl12(CH3OH)4(OCH3)2] ⋅ DABCO ⋅ 1.66 CH2Cl2
BT - cluster units wrapped in a network of hydrogen bonds
JF - Zeitschrift für anorganische und allgemeine Chemie : ZAAC = Journal of inorganic and general chemistry
N2 - An easy-to-do synthesis for the hexanuclear niobium cluster compound [Nb6Cl12(CH3OH)(4)(OCH3)(2)] . DABCO . 1.66 CH2Cl2 has been developed. An one-pot reaction between the cluster precursor [Nb6Cl14(H2O)(4)] . 4H(2)O and methanol with the addition of DABCO leads to the crystallization of the title compound in high yield within a few minutes. The single-crystal X-ray structure of this cluster compound has been determined. Very strong, nearly symmetric intercluster hydrogen bonds Nb-6-MeO...H...OMe-Nb-6 are present between the cluster units. A bridging co-crystalline DABCO molecule is also involved in a three-dimensional hydrogen-bonding network.
KW - Niobium
KW - Cluster
KW - Hydrogen Bonds
KW - Synthesis
KW - Structure Determination
Y1 - 2021
U6 - https://doi.org/10.1002/zaac.202100138
SN - 0044-2313
SN - 1521-3749
VL - 647
IS - 18
SP - 1759
EP - 1763
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Debsharma, Tapas
A1 - Schmidt, Bernd
A1 - Laschewsky, Andre
A1 - Schlaad, Helmut
T1 - Ring-opening metathesis polymerization of unsaturated carbohydrate derivatives
BT - levoglucosenyl alkyl ethers
JF - Macromolecules : a publication of the American Chemical Society
N2 - A series of biomass-derived levoglucosenyl alkyl ethers (alkyl = methyl, ethyl, n-propyl, isopropyl, and n-butyl) were synthesized and polymerized by ring-opening olefin metathesis polymerization using the Grubbs catalyst C793 at room temperature. Polymerizations were successfully performed in conventional solvents such as 1,4-dioxane and dichloromethane as well as in polar aprotic "green" solvents such as 2-methyltetrahydrofuran, dihydrolevoglucosenone (Cyrene), and ethyl acetate. The prepared polyacetals with degrees of polymerization of similar to 100 exhibit Schulz-Flory-type molar mass distributions and are thermoplastic materials with rather low glass transition temperatures in the range of 43-0 degrees C depending on the length of the alkyl substituent. Kinetic studies revealed that the polymerization proceeded rapidly to a steady state with a certain minimum monomer concentration threshold. When the steady state was reached, just about half of the [Ru] catalyst had been effective to initiate the polymerization, indicating that the initiation step was a slow process. The remaining catalyst was still active and did no longer react with monomers but with in-chain double bonds, cutting the formed polymer chains into shorter fragments. In the long term, all catalyst was consumed and propagating [Ru] chain ends were deactivated by the elimination of [Ru] from the chain ends to form inactive chains with terminal aldehyde groups.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.macromol.0c02821
SN - 0024-9297
SN - 1520-5835
VL - 54
IS - 6
SP - 2720
EP - 2728
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Liang, Xiao
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Dihydroxy terminated teroligomers from morpholine-2,5-diones
JF - European polymer journal : EPJ
N2 - Oligodepsipeptides (ODPs) attract increasing attention as degradable materials in controlled drug delivery or as building blocks for nano-carriers. Their strong intermolecular interactions provide high stability. Tailoring the side groups of the amino acid repeating units to achieve a strong affinity to particular drugs allows a high drug-loading capacity. Here we describe synthesis and characterization of dihydroxy terminated teroligodepsipeptides (ter-ODPs) by ring-opening copolymerization (ROP) of three different morpholine-2,5-diones (MDs) in bulk in order to provide a set of teroligomers with structural variation for drug release or transfection. Ter-ODPs with equivalent co-monomer feed ratios were prepared as well as ter-ODPs, in which the co-monomer feed ratio was varied between 9 mol% and 78 mol%. Ter-ODPs were synthesized by ROP using 1,1,10,10-tetra-n-butyl-1,10-distanna-2,9,11,18-tetraoxa-5,6,14,15-tetrasulfur-cyclodecane (tin(IV) alkoxide) that was obtained by the reaction of dibutyl tin(II) oxide with 2-hydroxyethyl disulfide. The number average molecular weight (M-n) of ter-ODPs, determined by H-1 NMR and gel permeation chromatography (GPC), ranged between 4000 g center dot mol(-1) and 8600 g center dot mol(-1). Co-monomer compositions in ter-ODPs could be controlled by changing the feed ratio of co-monomers as observed by H-1 NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The amount of remaining monomers as determined by H-1 NMR could be kept below 1 wt%. Macrocycles as main sources of byproducts as determined from MALDI-TOF-MS measurements were significantly lower as compared to polymerization by Sn(Oct)(2). Glass-transition temperature (T-g) of ter-ODPs ranged between 59 degrees C and 70 degrees C.
KW - Ring-opening polymerization
KW - Tin octanoate
KW - Morpholindione
KW - Depsipeptide
KW - Random copolymer
KW - Telechel
Y1 - 2021
U6 - https://doi.org/10.1016/j.eurpolymj.2020.110189
SN - 0014-3057
VL - 143
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Sauter, Tilman
A1 - Kratz, Karl
A1 - Heuchel, Matthias
A1 - Lendlein, Andreas
T1 - Fiber diameter as design parameter for tailoring the macroscopic shape-memory performance of electrospun meshes
JF - Materials and design
N2 - Fibrous shape-memory polymer (SMP) scaffolds were investigated considering the fiber as basic microstructural feature. By reduction of the fiber diameter in randomly oriented electrospun polyetherurethane (PEU) meshes from the micro-to the nano-scale, we observed changes in the molecular orientation within the fibers and its impact on the structural and shape-memory performance. It was assumed that a spatial restriction by reduction of the fiber diameter increases molecular orientation along the orientation of the fiber. The stress-strain relation of random PEU scaffolds is initially determined by the 3D arrangement of the fibers and thus is independent of the molecular orientation. Increasing the molecular orientation with decreasing single fiber diameter in scaffolds composed of randomly arranged fibers did not alter the initial stiffness and peak stress but strongly influenced the elongation at break and the stress increase above the Yield point. Reduction of the single fiber diameter also distinctly improved the shape-memory performance of the scaffolds. Fibers with nanoscale diameters (< 100 nm) possessed an almost complete shape recovery, high recovery stresses and fast relaxation kinetics, while the shape fixity was found to decrease with decreasing fiber diameter. Hence, the fiber diameter is a relevant design parameter for SMP.
KW - Nanofiber
KW - Shape-memory polymer
KW - Electrospinning
KW - Function by design
KW - Molecular orientation
Y1 - 2021
U6 - https://doi.org/10.1016/j.matdes.2021.109546
SN - 1873-4197
VL - 202
PB - Elsevier
CY - Amsterdam [u.a.]
ER -
TY - JOUR
A1 - Bastian, Philipp U.
A1 - Robel, Nathalie
A1 - Schmidt, Peter
A1 - Schrumpf, Tim
A1 - Günter, Christina
A1 - Roddatis, Vladimir
A1 - Kumke, Michael U.
T1 - Resonance energy transfer to track the motion of lanthanide ions
BT - what drives the intermixing in core-shell upconverting nanoparticles?
JF - Biosensors : open access journal
N2 - The imagination of clearly separated core-shell structures is already outdated by the fact, that the nanoparticle core-shell structures remain in terms of efficiency behind their respective bulk material due to intermixing between core and shell dopant ions. In order to optimize the photoluminescence of core-shell UCNP the intermixing should be as small as possible and therefore, key parameters of this process need to be identified. In the present work the Ln(III) ion migration in the host lattices NaYF4 and NaGdF4 was monitored. These investigations have been performed by laser spectroscopy with help of lanthanide resonance energy transfer (LRET) between Eu(III) as donor and Pr(III) or Nd(III) as acceptor. The LRET is evaluated based on the Forster theory. The findings corroborate the literature and point out the migration of ions in the host lattices. Based on the introduced LRET model, the acceptor concentration in the surrounding of one donor depends clearly on the design of the applied core-shell-shell nanoparticles. In general, thinner intermediate insulating shells lead to higher acceptor concentration, stronger quenching of the Eu(III) donor and subsequently stronger sensitization of the Pr(III) or the Nd(III) acceptors. The choice of the host lattice as well as of the synthesis temperature are parameters to be considered for the intermixing process.
KW - upconversion nanoparticles
KW - lanthanoid migration
KW - lanthanides
KW - core-shell
KW - energy transfer
Y1 - 2021
U6 - https://doi.org/10.3390/bios11120515
SN - 2079-6374
VL - 11
IS - 12
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Behl, Marc
A1 - Balk, Maria
A1 - Mansfeld, Ulrich
A1 - Lendlein, Andreas
T1 - Phase morphology of multiblock copolymers differing in sequence of blocks
JF - Macromolecular materials and engineering
N2 - The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. It is hypothesized that a strictly alternating sequence should impact phase segregation. A library of well-defined MBC obtained by coupling oligo(epsilon-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification results in strictly alternating (MBCalt) or random (MBCran) MBC. The three different series has a weight average molecular weight (M-w) of 65 000, 165 000, and 168 000 g mol(-1) for MBCalt and 80 500, 100 000, and 147 600 g mol(-1) for MBCran. When the chain length of OCL building blocks is increased, the tendency for phase segregation is facilitated, which is attributed to the decrease in chain mobility within the MBC. Furthermore, it is found that the phase segregation disturbs the crystallization by causing heterogeneities in the semi-crystalline alignment, which is attributed to an increase of the disorder of the OCL semi-crystalline alignment.
KW - electron microscopy
KW - multiblock copolymers
KW - phase morphology
KW - polymer
KW - libraries
KW - sequence structures
KW - wide angle x‐ ray scattering
Y1 - 2021
U6 - https://doi.org/10.1002/mame.202000672
SN - 1439-2054
VL - 306
IS - 3
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Pan, Mengdi
A1 - Schicks, Judith M.
T1 - Influence of gas supply changes on the formation process of complex mixed gas hydrates
JF - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2 - Natural gas hydrate occurrences contain predominantly methane; however, there are increasing reports of complex mixed gas hydrates and coexisting hydrate phases. Changes in the feed gas composition due to the preferred incorporation of certain components into the hydrate phase and an inadequate gas supply is often assumed to be the cause of coexisting hydrate phases. This could also be the case for the gas hydrate system in Qilian Mountain permafrost (QMP), which is mainly controlled by pores and fractures with complex gas compositions. This study is dedicated to the experimental investigations on the formation process of mixed gas hydrates based on the reservoir conditions in QMP. Hydrates were synthesized from water and a gas mixture under different gas supply conditions to study the effects on the hydrate formation process. In situ Raman spectroscopic measurements and microscopic observations were applied to record changes in both gas and hydrate phase over the whole formation process. The results demonstrated the effects of gas flow on the composition of the resulting hydrate phase, indicating a competitive enclathration of guest molecules into the hydrate lattice depending on their properties. Another observation was that despite significant changes in the gas composition, no coexisting hydrate phases were formed.
KW - mixed gas hydrates
KW - hydrate formation process
KW - coexisting phases
KW - in
KW - situ Raman spectroscopy
KW - gas supply conditions
Y1 - 2021
U6 - https://doi.org/10.3390/molecules26103039
SN - 1420-3049
VL - 26
IS - 10
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Doering, Ulrike
A1 - Grigoriev, Dmitry
A1 - Tapio, Kosti
A1 - Rosencrantz, Sophia
A1 - Rosencrantz, Ruben R.
A1 - Bald, Ilko
A1 - Böker, Alexander
T1 - About the mechanism of ultrasonically induced protein capsule formation
JF - RSC Advances : an international journal to further the chemical sciences / Royal Society of Chemistry
N2 - In this paper, we propose a consistent mechanism of protein microcapsule formation upon ultrasound treatment. Aqueous suspensions of bovine serum albumin (BSA) microcapsules filled with toluene are prepared by use of high-intensity ultrasound following a reported method. Stabilization of the oil-in-water emulsion by the adsorption of the protein molecules at the interface of the emulsion droplets is accompanied by the creation of the cross-linked capsule shell due to formation of intermolecular disulfide bonds caused by highly reactive species like superoxide radicals generated sonochemically. The evidence for this mechanism, which until now remained elusive and was not proven properly, is presented based on experimental data from SDS-PAGE, Raman spectroscopy and dynamic light scattering.
Y1 - 2021
U6 - https://doi.org/10.1039/d0ra08100k
SN - 2046-2069
VL - 11
IS - 27
SP - 16152
EP - 16157
PB - RSC Publishing
CY - London
ER -
TY - JOUR
A1 - Kogikoski Junior, Sergio
A1 - Tapio, Kosti
A1 - Edler von Zander, Robert
A1 - Saalfrank, Peter
A1 - Bald, Ilko
T1 - Raman enhancement of nanoparticle dimers self-assembled using DNA origami nanotriangles
JF - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2 - Surface-enhanced Raman scattering is a powerful approach to detect molecules at very low concentrations, even up to the single-molecule level. One important aspect of the materials used in such a technique is how much the signal is intensified, quantified by the enhancement factor (EF). Herein we obtained the EFs for gold nanoparticle dimers of 60 and 80 nm diameter, respectively, self-assembled using DNA origami nanotriangles. Cy5 and TAMRA were used as surface-enhanced Raman scattering (SERS) probes, which enable the observation of individual nanoparticles and dimers. EF distributions are determined at four distinct wavelengths based on the measurements of around 1000 individual dimer structures. The obtained results show that the EFs for the dimeric assemblies follow a log-normal distribution and are in the range of 10(6) at 633 nm and that the contribution of the molecular resonance effect to the EF is around 2, also showing that the plasmonic resonance is the main source of the observed signal. To support our studies, FDTD simulations of the nanoparticle's electromagnetic field enhancement has been carried out, as well as calculations of the resonance Raman spectra of the dyes using DFT. We observe a very close agreement between the experimental EF distribution and the simulated values.
KW - surface-enhanced Raman scattering
KW - DNA origami
KW - resonance Raman
KW - scattering
KW - nanoparticle dimers
Y1 - 2021
U6 - https://doi.org/10.3390/molecules26061684
SN - 1420-3049
VL - 26
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Fortes Martín, Rebeca
A1 - Thünemann, Andreas F.
A1 - Stockmann, Jörg M.
A1 - Radnik, Jörg
A1 - Koetz, Joachim
T1 - From nanoparticle heteroclusters to filament networks by self-assembly at the water-oil interface of reverse microemulsions
JF - Langmuir : the ACS journal of surfaces and colloids / American Chemical Society
N2 - Surface self-assembly of spherical nanoparticles of sizes below 10 nm into hierarchical heterostructures is under arising development despite the inherent difficulties of obtaining complex ordering patterns on a larger scale. Due to template-mediated interactions between oil-dispersible superparamagnetic nanoparticles (MNPs) and polyethylenimine- stabilized gold nanoparticles (Au(PEI)NPs) at the water-oil interface of microemulsions, complex nanostructured films can be formed. Characterization of the reverse microemulsion phase by UV-vis absorption revealed the formation of heteroclusters from Winsor type II phases (WPII) using Aerosol-OT (AOT) as the surfactant. SAXS measurements verify the mechanism of initial nanoparticle clustering in defined dimensions. XPS suggested an influence of AOT at the MNP surface. Further, cryo-SEM and TEM visualization demonstrated the elongation of the reverse microemulsions into cylindrical, wormlike structures, which subsequently build up larger nanoparticle superstructure arrangements. Such WPII phases are thus proven to be a new form of soft template, mediating the self-assembly of different nanoparticles in hierarchical network-like filaments over a substrate during solvent evaporation.
KW - Emulsions
KW - Liquids
KW - Nanoparticles
KW - Water
KW - X-ray scattering
Y1 - 2021
U6 - https://doi.org/10.1021/acs.langmuir.1c01348
SN - 0743-7463
VL - 37
IS - 29
SP - 8876
EP - 8885
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Dutta, Anushree
A1 - Schürmann, Robin
A1 - Kogikoski Junior, Sergio
A1 - Mueller, Niclas S.
A1 - Reich, Stephanie
A1 - Bald, Ilko
T1 - Kinetics and mechanism of plasmon-driven dehalogenation reaction of brominated purine nucleobases on Ag and Au
JF - ACS catalysis / American Chemical Society
N2 - Plasmon-driven photocatalysis is an emerging and promising application of noble metal nanoparticles (NPs). An understanding of the fundamental aspects of plasmon interaction with molecules and factors controlling their reaction rate in a heterogeneous system is of high importance. Therefore, the dehalogenation kinetics of 8-bromoguanine (BrGua) and 8-bromoadenine (BrAde) on aggregated surfaces of silver (Ag) and gold (Au) NPs have been studied to understand the reaction kinetics and the underlying reaction mechanism prevalent in heterogeneous reaction systems induced by plasmons monitored by surface enhanced Raman scattering (SERS). We conclude that the time-average constant concentration of hot electrons and the time scale of dissociation of transient negative ions (TNI) are crucial in defining the reaction rate law based on a proposed kinetic model. An overall higher reaction rate of dehalogenation is observed on Ag compared with Au, which is explained by the favorable hot-hole scavenging by the reaction product and the byproduct. We therefore arrive at the conclusion that insufficient hole deactivation could retard the reaction rate significantly, marking itself as rate-determining step for the overall reaction. The wavelength dependency of the reaction rate normalized to absorbed optical power indicates the nonthermal nature of the plasmon-driven reaction. The study therefore lays a general approach toward understanding the kinetics and reaction mechanism of a plasmon-driven reaction in a heterogeneous system, and furthermore, it leads to a better understanding of the reactivity of brominated purine derivatives on Ag and Au, which could in the future be exploited, for example, in plasmon-assisted cancer therapy.
KW - hot-electrons
KW - plasmon-driven catalysis
KW - fractal kinetics
KW - brominated
KW - purines
KW - SERS
KW - hole scavengers
Y1 - 2021
U6 - https://doi.org/10.1021/acscatal.1c01851
SN - 2155-5435
VL - 11
IS - 13
SP - 8370
EP - 8381
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Keckeis, Philipp
A1 - Zeller, Enriko
A1 - Jung, Carina
A1 - Besirske, Patricia
A1 - Kirner, Felizitas
A1 - Ruiz-Agudo, Cristina
A1 - Schlaad, Helmut
A1 - Cölfen, Helmut
T1 - Modular toolkit of multifunctional block copoly(2-oxazoline)s for the synthesis of nanoparticles
JF - Chemistry - a European journal
N2 - Post-polymerization modification provides an elegant way to introduce chemical functionalities onto macromolecules to produce tailor-made materials with superior properties. This concept was adapted to well-defined block copolymers of the poly(2-oxazoline) family and demonstrated the large potential of these macromolecules as universal toolkit for numerous applications. Triblock copolymers with separated water-soluble, alkyne- and alkene-containing segments were synthesized and orthogonally modified with various low-molecular weight functional molecules by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and thiol-ene (TE) click reactions, respectively. Representative toolkit polymers were used for the synthesis of gold, iron oxide and silica nanoparticles.
KW - block copolymers
KW - click chemistry
KW - nanoparticles
KW - ring-opening
KW - polymerization
KW - surfactants
Y1 - 2021
U6 - https://doi.org/10.1002/chem.202101327
SN - 0947-6539
SN - 1521-3765
VL - 27
IS - 32
SP - 8283
EP - 8287
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Witzorky, Christoph
A1 - Paramonov, Guennaddi
A1 - Bouakline, Foudhil
A1 - Jaquet, Ralph
A1 - Saalfrank, Peter
A1 - Klamroth, Tillmann
T1 - Gaussian-type orbital calculations for high harmonic generation in vibrating molecules
BT - Benchmarks for H-2(+)
JF - Journal of chemical theory and computation
N2 - The response of the hydrogen molecular ion, H-2(+), to few-cycle laser pulses of different intensities is simulated. To treat the coupled electron-nuclear motion, we use adiabatic potentials computed with Gaussian-type basis sets together with a heuristic ionization model for the electron and a grid representation for the nuclei. Using this mixed-basis approach, the time-dependent Schrodinger equation is solved, either within the Born-Oppenheimer approximation or with nonadiabatic couplings included. The dipole response spectra are compared to all-grid-based solutions for the three-body problem, which we take as a reference to benchmark the Gaussian-type basis set approaches. Also, calculations employing the fixed-nuclei approximation are performed, to quantify effects due to nuclear motion. For low intensities and small ionization probabilities, we get excellent agreement of the dynamics using Gaussian-type basis sets with the all-grid solutions. Our investigations suggest that high harmonic generation (HHG) and high-frequency response, in general, can be reliably modeled using Gaussian-type basis sets for the electrons for not too high harmonics. Further, nuclear motion destroys electronic coherences in the response spectra even on the time scale of about 30 fs and affects HHG intensities, which reflect the electron dynamics occurring on the attosecond time scale. For the present system, non-Born-Oppenheimer effects are small. The Gaussian-based, nonadiabatically coupled, time-dependent multisurface approach to treat quantum electron-nuclear motion beyond the non-Born-Oppenheimer approximation can be easily extended to approximate wavefunction methods, such as time-dependent configuration interaction singles (TD-CIS), for systems where no benchmarks are available.
KW - Basis sets
KW - Chemical calculations
KW - Ionization
KW - Lasers
KW - Quantum mechanics
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jctc.1c00837
SN - 1549-9618
SN - 1549-9626
VL - 17
IS - 12
SP - 7353
EP - 7365
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Lendlein, Andreas
A1 - Heuchel, Matthias
T1 - Shape-memory polymers designed in view of thermomechanical energy storage and conversion systems
BT - Effective temporary shape fixation by strain-induced formation of supramolecular nanostructures enables high energy density one-way shape-memory polymers
JF - ACS central science
KW - Actuators
KW - Deformation
KW - Energy
KW - Energy storage
KW - Polymers
Y1 - 2021
U6 - https://doi.org/10.1021/acscentsci.1c01032
SN - 2374-7951
VL - 7
IS - 10
SP - 1599
EP - 1601
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Gaebel, Tina
A1 - Bein, Daniel
A1 - Mathauer, Daniel
A1 - Utecht, Manuel
A1 - Palmer, Richard E.
A1 - Klamroth, Tillmann
T1 - Nonlocal STM manipulation of chlorobenzene on Si(111)-7 x 7
BT - Potentials, kinetics, and first-principles molecular dynamics calculations for open systems
JF - The journal of physical chemistry : C, Nanomaterials and interfaces
N2 - We use quantum chemical cluster models together with constrained density STM Ph CI functional theory (DFT) and ab initio molecular dynamics (AIMD) for open system to simulate tip and rationalize nonlocal scanning tunneling microscope (STM) manipulation experiments for Philh ci chlorobenzene (PhCl) on a Si(111)-7 X 7 surface. We consider three different processes, namely, the electron-induced dissociation of the carbon-chlorine bond for physisorbed PhCl molecules at low temperatures and the electron- or hole-induced desorption of chemisorbed PhCl at 300 K. All processes can be induced nonlocally, i.e., up to several nanometers (nm) away from the injection site, in STM experiments. We rationalize and explain the experimental findings regarding the STM-induced dissociation using constrained DFT. The coupling of STM-induced ion resonances to nuclear degrees of freedom is simulated with AIMD using the Gadzuk averaging approach for open systems. From this data, we predict a 4 fs lifetime for the cationic resonance. For the anion model, desorption could not be observed. In addition, the same cluster models are used for transition-state theory calculations, which are compared to and validated against time-lapse STM experiments.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jpcc.1c02612
SN - 1932-7447
SN - 1932-7455
VL - 125
IS - 22
SP - 12175
EP - 12184
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Wojnarowska, Zaneta
A1 - Lange, Alyna
A1 - Taubert, Andreas
A1 - Paluch, Marian
T1 - Ion and proton transport in aqueous/nonaqueous acidic tonic liquids for fuel-cell applications-insight from high-pressure dielectric studies
JF - ACS applied materials & interfaces / American Chemical Society
N2 - The use of acidic ionic liquids and solids as electrolytes in fuel cells is an emerging field due to their efficient proton conductivity and good thermal stability. Despite multiple reports describing conducting properties of acidic ILs, little is known on the charge-transport mechanism in the vicinity of liquid-glass transition and the structural factors governing the proton hopping. To address these issues, we studied two acidic imidazolium-based ILs with the same cation, however, different anions-bulk tosylate vs small methanesulfonate. High-pressure dielectric studies of anhydrous and water-saturated materials performed in the close vicinity of T-g have revealed significant differences in the charge-transport mechanism in these two systems being undetectable at ambient conditions. Thereby, we demonstrated the effect of molecular architecture on proton hopping, being crucial in the potential electrochemical applications of acidic ILs.
KW - proton hopping
KW - dielectric spectroscopy
KW - high pressure
KW - ion transport
KW - acidic ionic liquids
Y1 - 2021
U6 - https://doi.org/10.1021/acsami.1c06260
SN - 1944-8244
SN - 1944-8252
VL - 13
IS - 26
SP - 30614
EP - 30624
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Liang, Xiao
A1 - Behl, Marc
A1 - Lützow, Karola
A1 - Lendlein, Andreas
T1 - Cooligomers from morpholine-2,5-dione and para-dioxanone and catalyst complex SnOct(2)/2-hydroxyethyl sulfide
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - Complexes from catalysts and initiator can be used to insert a specific number of additional chemical functional groups in (co)polymers prepared by ring-opening polymerization (ROP) of lactones. We report on the synthesis of cooligomers from sec-butyl-morpholine-2,5-dione (SBMD) and para-dioxanone (PDX) by ROP with varied feed ratios in the bulk using the catalyst complex SnOct(2)/2-hydroxyethyl sulfide. M-n of the cooligomers (determined by GPC) decreased with decreasing SBMD feed ratio from 4200 +/- 420 to 800 +/- 80 g mol(-1). When the feed ratio was reduced from 80 to 50 mol% the molar ratio of SBMD of the cooligomers (determined by H-1-NMR) remained nearly unchanged between 81 and 86 mol% and was attributed to a higher reactivity of SBMD. This assumption was confirmed by fractionation of GPC, in which an increase of SBMD with increasing molecular weight was observed. The catalyst/initiator system provides a high potential to create orthogonal building blocks by cleavage of the sulfide bond.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00082-5
SN - 2059-8521
VL - 6
IS - 32
SP - 764
EP - 768
PB - Springer
CY - Heidelberg
ER -
TY - JOUR
A1 - López-Salas, Nieves
A1 - Albero, Josep
T1 - CxNy
BT - new carbon nitride organic photocatalysts
JF - Frontiers in Materials
N2 - The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials.
KW - CXNY
KW - carbon nitrides
KW - C2N
KW - C3N
KW - C1N1
KW - C3N5
KW - photocatalysis
Y1 - 2021
U6 - https://doi.org/10.3389/fmats.2021.772200
SN - 2296-8016
VL - 8
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Neffe, Axel T.
A1 - Izraylit, Victor
A1 - Hommes-Schattmann, Paul J.
A1 - Lendlein, Andreas
T1 - Soft, formstable (Co)polyester blend elastomers
JF - Nanomaterials : open access journal
N2 - High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(epsilon-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature T-g <= 0 degrees C of the mixed amorphous phase contributes to the low Young's modulus E. The formation of stereocomplexes is shown in DSC by melting transitions T-m > 190 degrees C and in WAXS by distinct scattering maxima at 2 theta = 12 degrees and 21 degrees. Tensile testing demonstrated that the blends are soft (E = 12-80 MPa) and show an excellent hyperelastic recovery R-rec = 66-85% while having high elongation at break epsilon(b) up to >1000%. These properties of the blends are attained only when the copolymer has 56-62 wt% lactide content, a weight average molar mass >140 kg center dot mol(-1), and number average lactide sequence length >= 4.8, while the blend is formed with a content of 5-10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications.
KW - thermoplastic elastomer
KW - biomaterial
KW - stereocomplexes
KW - mechanical
KW - properties
KW - form stability
KW - crystallinity
Y1 - 2021
U6 - https://doi.org/10.3390/nano11061472
SN - 2079-4991
VL - 11
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Bäckemo, Johan Dag Valentin
A1 - Liu, Yue
A1 - Lendlein, Andreas
T1 - Bio-inspired and computer-supported design of modulated shape changes in polymer materials
JF - MRS communications / a publication of the Materials Research Society
N2 - The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap.
KW - Additive manufacturing
KW - Biomimetic
KW - Shape memory
KW - Modelling
KW - Polymer
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00056-6
SN - 2159-6867
VL - 11
IS - 4
SP - 462
EP - 469
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Farhan, Muhammad
A1 - Behl, Marc
A1 - Kratz, Karl
A1 - Lendlein, Andreas
T1 - Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators
JF - MRS communications / a publication of the Materials Research Society
N2 - Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg(-1) was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling.
KW - Robotics
KW - Polymer
KW - Fiber
KW - Actuation
KW - Shape-memory
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00058-4
SN - 2159-6859
SN - 2159-6867
VL - 11
IS - 4
SP - 476
EP - 482
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Izraylit, Victor
A1 - Liu, Yue
A1 - Tarazona, Natalia A.
A1 - Machatschek, Rainhard Gabriel
A1 - Lendlein, Andreas
T1 - Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers
JF - MRS communications / a publication of the Materials Research Society
N2 - Supporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend's flexibility.
KW - Degradable
KW - In situ
KW - Microstructure
KW - Thin film
Y1 - 2021
U6 - https://doi.org/10.1557/s43579-021-00107-y
SN - 2159-6859
SN - 2159-6867
VL - 11
IS - 6
SP - 850
EP - 855
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Izraylit, Victor
A1 - Heuchel, Matthias
A1 - Kratz, Karl
A1 - Lendlein, Andreas
T1 - Non-woven shape-memory polymer blend actuators
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - The hierarchical design approach provides various opportunities to adjust the structural performance of polymer materials. Electrospinning processing techniques give access to molecular orientation as a design parameter, which we consider here in view of the shape-memory actuation performance. The aim of this work is to investigate how the reversible strain epsilon'(rev) can be affected by a morphology change from a bulk material to an electrospun mesh. epsilon'(rev) could be increased from 5.5 +/- 0.5% to 15 +/- 1.8% for a blend from a multiblock copolymer with poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA) segments with oligo(D-lactide) (ODLA). This study demonstrates an effective design approach for enhancing soft actuator performance, which can be broadly applied in soft robotics and medicine.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00063-8
SN - 2059-8521
VL - 6
IS - 33
SP - 781
EP - 785
PB - Springer Nature Switzerland AG
CY - Cham
ER -
TY - JOUR
A1 - Kleinpeter, Erich
A1 - Koch, Andreas
T1 - Dative or coordinative carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs)?
BT - an answer given on the magnetic criterion
JF - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of isolated as well as B-C bond length varied model compounds (BR3 trapped NHCs) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the present dative vs. coordinative bond character of the boron-carbon bond in the trapped NHCs. Results are confirmed by bond lengths and B-11/C-13 chemical shift variations in the BR3 trapped NHCs.
KW - NHCs
KW - Dative vs. coordinative NHC -> BR3 bond
KW - Through-space NMR
KW - shieldings (TSNMRS)
KW - NICS
KW - Anisotropy effect
Y1 - 2021
U6 - https://doi.org/10.1016/j.tet.2020.131787
SN - 0040-4020
SN - 1464-5416
VL - 80
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Neffe, Axel T.
A1 - Zhang, Quanchao
A1 - Hommes-Schattmann, Paul J.
A1 - Lendlein, Andreas
T1 - Ethylene oxide sterilization of electrospun poly(L-lactide)/poly(D-lactide) core/shell nanofibers
JF - MRS advances
N2 - The application of polymers in medicine requires sterilization while retaining material structure and properties. This demands detailed analysis, which we show exemplarily for the sterilization of PLLA/PDLA core-shell nanofibers with ethylene oxide (EtO). The electrospun patch was exposed to EtO gas (6 vol% in CO2, 1.7 bar) for 3 h at 45 degrees C and 75% rel. humidity, followed by degassing under pressure/vacuum cycles for 12 h. GC-MS analysis showed that no residual EtO was retained. Fiber diameters (similar to 520 +/- 130 nm) of the patches remained constant as observed by electron microscopy. Young's modulus slightly increased and the elongation at break slightly decreased, determined at 37 degrees C. No changes were detected in H-1-NMR spectra, in molar mass distribution (GPC) or in crystallinity measured for annealed samples with comparable thermal history (Wide Angle X-Ray Scattering). Altogether, EtO emerged as suitable sterilization method for polylactide nanofibers with core-shell morphology.
Y1 - 2021
U6 - https://doi.org/10.1557/s43580-021-00058-5
SN - 2059-8521
VL - 6
IS - 33
SP - 786
EP - 789
PB - Springer
CY - Cham
ER -
TY - JOUR
A1 - Picconi, David
T1 - Nonadiabatic quantum dynamics of the coherent excited state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline
JF - Photochemical & photobiological sciences
N2 - The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone.
[GRAPHICS]
.
KW - Excited state proton transfer
KW - Quantum dynamics
KW - Nonadiabatic effects
KW - Spectroscopy
KW - Coherences
Y1 - 2021
U6 - https://doi.org/10.1007/s43630-021-00112-z
SN - 1474-905X
SN - 1474-9092
VL - 20
IS - 11
SP - 1455
EP - 1473
PB - Springer
CY - Heidelberg
ER -
TY - JOUR
A1 - Kleinpeter, Erich
A1 - Koch, Andreas
T1 - Quantification of sigma-acceptor and pi-donor stabilization in O, S and Hal analogues of N-heterocyclic carbenes (NHCs) on the magnetic criterion
JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of stable O, S and Hal analogues of N-heterocyclic carbenes (NHCs) have been calculated using the GIAO perturbation method employing the nucleus-independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSSs) of various sizes and directions. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the position of the present mesomeric equilibria (carbenes <-> ylides). The results are confirmed by geometry (bond angles and bond lengths), IR spectra, UV spectra, and C-13 chemical shifts of the electron-deficient carbon centers.
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jpca.1c05257
SN - 1089-5639
SN - 1520-5215
VL - 125
IS - 33
SP - 7235
EP - 7245
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Hermanns, Jolanda
A1 - Keller, David
T1 - School-related content knowledge in organic chemistry
BT - How does the Bachelor and Master studies?
JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2 - In this paper the development, use, and evaluation of tasks based on the construct of school-related content knowledge are described. The tasks were used in seminars on organic chemistry for bachelor and master preservice chemistry teachers at a German university. For the evaluation a questionnaire with open and closed items was used. The tasks were rated by the preservice chemistry teachers as relevant for their future profession as a chemistry teacher if the content of the tasks is part of the school curriculum. If the content does not belong to the school curriculum, they rated the nature of the tasks still as relevant; they seem to recognize the importance of conceptual knowledge for their future profession. However, the master's preservice teachers argued with this conceptual knowledge more often than the bachelor's preservice teachers. Although the study is cross-sectional, a certain shift from the focus on the content to conceptual knowledge from bachelor's to master's preservice teachers can be observed.
KW - Organic Chemistry
KW - Second-Year Undergraduate
KW - Analogies/Transfer
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jchemed.0c01415
SN - 0021-9584
SN - 1938-1328
VL - 98
IS - 3
SP - 763
EP - 773
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Kleinpeter, Erich
A1 - Koch, Andreas
T1 - Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion
JF - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre.
KW - Cyclobutylcarbene
KW - 1,2-diboretane-3-ylidene
KW - 3c,2e-bonding
KW - Through-space NMR shieldings (TSNMRS)
KW - NICS
Y1 - 2021
U6 - https://doi.org/10.1016/j.tet.2021.132357
SN - 0040-4020
SN - 1464-5416
VL - 95
PB - Elsevier Science
CY - Amsterdam
ER -
TY - JOUR
A1 - Krüger, Tobias
A1 - Linker, Torsten
T1 - Synthesis of gamma-spirolactams by Birch reduction of arenes
JF - European journal of organic chemistry
N2 - A convenient method for the synthesis of gamma-spirolactams in only three steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of chloroacetonitrile affords nitriles in moderate to good yields. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and anthroic acid. Subsequent catalytic hydrogenation proceeds smoothly with PtO2 or Raney Ni as catalysts and lactams are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation at different pressures, affording products with 0, 1, or 2 double bonds. Overall, more than 15 new gamma-spirolactams have been synthesized in analytically pure form.
KW - Arenes
KW - Birch reduction
KW - Hydrogenation
KW - Lactams
KW - Synthetic methods
Y1 - 2021
U6 - https://doi.org/10.1002/ejoc.202100056
SN - 1099-0690
VL - 2021
IS - 10
SP - 1585
EP - 1591
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Titov, Evgenii
T1 - On the low-lying electronically excited states of azobenzene dimers
BT - Transition density matrix analysis
JF - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2 - Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest pi pi* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used.
KW - azobenzene
KW - dimer
KW - transition density matrix
KW - exciton
KW - charge transfer
KW - excited states
KW - TD-DFT
KW - ADC(2)
Y1 - 2021
U6 - https://doi.org/10.3390/molecules26144245
SN - 1420-3049
VL - 26
IS - 14
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Fischer, Eric W.
A1 - Saalfrank, Peter
T1 - A thermofield-based multilayer multiconfigurational time-dependent Hartree approach to non-adiabatic quantum dynamics at finite temperature
JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2 - We introduce a thermofield-based formulation of the multilayer multiconfigurational time-dependent Hartree (MCTDH) method to study finite temperature effects on non-adiabatic quantum dynamics from a non-stochastic, wave function perspective. Our approach is based on the formal equivalence of bosonic many-body theory at zero temperature with a doubled number of degrees of freedom and the thermal quasi-particle representation of bosonic thermofield dynamics (TFD). This equivalence allows for a transfer of bosonic many-body MCTDH as introduced by Wang and Thoss to the finite temperature framework of thermal quasi-particle TFD. As an application, we study temperature effects on the ultrafast internal conversion dynamics in pyrazine. We show that finite temperature effects can be efficiently accounted for in the construction of multilayer expansions of thermofield states in the framework presented herein. Furthermore, we find our results to agree well with existing studies on the pyrazine model based on the pMCTDH method.
Y1 - 2021
U6 - https://doi.org/10.1063/5.0064013
SN - 0021-9606
SN - 1089-7690
VL - 155
IS - 13
PB - American Institute of Physics
CY - Melville
ER -
TY - JOUR
A1 - Krause, Andreas
A1 - Sperlich, Eric
A1 - Schmidt, Bernd
T1 - Matsuda-Heck arylation of itaconates
BT - a versatile approach to heterocycles from a renewable resource
JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry
N2 - Itaconic acid esters and hemiesters undergo Pd-catalyzed coupling reactions with arene diazonium salts in high to excellent yields. The coupling products of ortho-nitro arene diazonium salts can be converted in one or two steps to benzazepine-2-ones.
Y1 - 2021
U6 - https://doi.org/10.1039/d1ob00392e
SN - 1477-0520
SN - 1477-0539
VL - 19
IS - 19
SP - 4292
EP - 4302
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Hermanns, Jolanda
T1 - The task navigator following the STRAKNAP concept
BT - Development, application, and evaluation of a new scaffold to support nonmajor chemistry students while solving tasks in organic chemistry
JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2 - Educational Scaffolding was first mentioned in 1976 by Wood et al. Several examples for scaffolding in chemistry are also known from the literature. As written scaffolds, stepped supporting tools to support students while solving problems in organic chemistry were developed, applied, and evaluated. Although the students rated the tool as very helpful, a think-aloud study showed that the support given by this scaffold was not sufficient. As a further development of stepped supporting tools, task navigators were therefore developed, applied, and evaluated. This new scaffold gives tips on strategy, knowledge, and application of knowledge after the STRAKNAP concept. The evaluation of this tool shows that the students rated the tool as being very helpful. A think-aloud study showed that the scaffold supports the students while they solve a problem. Because of the stepwise construction of the task navigators and the providing of the knowledge needed for the application, the students can solve parts of the task successfully even if they do not solve all parts correctly; the students can always start from scratch. When students use the tool regularly, their knowledge of organic chemistry increases compared to students who did not use the tool at all. The task navigator is not only a scaffold for the content of the task but also for the development of methodological competences on the field of strategies and applying knowledge.
KW - First-Year Undergraduate/General
KW - Organic Chemistry
KW - Distance
KW - Learning/Chemistry Education Research
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jchemed.0c01162
SN - 0021-9584
SN - 1938-1328
VL - 98
IS - 4
SP - 1077
EP - 1087
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Bouakline, Foudhil
T1 - Umbrella inversion of ammonia redux
JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2 - Umbrella inversion of ammonia is a prototypical example of large-amplitude vibrational motion, described with a symmetric double-well potential. The transition state of the latter corresponds to a planar (D-3h) molecular geometry, whereas the two equilibrium configurations are equivalent (C-3v) pyramidal structures, with the nitrogen atom being either 'above' or 'below' the plane of the hydrogen atoms. As commonly understood, inversion motion of ammonia corresponds to the coherent, anharmonic, vibrational motion of the molecule, which shuttles back and forth between the two potential wells; that is, oscillation of the nitrogen atom from one side of the H-3 plane to the other, via coherent tunneling. However, this intuitively appealing view of umbrella inversion results from a reduced description of the dynamics, which includes only the inversion vibrational coordinate and fully neglects all the other molecular degrees of freedom. As such, this textbook picture of inversion motion ignores the fact that the two equilibrium structures of ammonia are superimposable, and can only be distinguished by labelling the identical hydrogen nuclei. A correct description of umbrella inversion, which incorporates nuclear permutations, requires the inclusion of other molecular modes. Indeed, it is well known that the quantum symmetrization postulate engenders entanglement between ammonia's nuclear-spin, inversion, and rotation. Using the explicit expressions of the corresponding zeroth-order eigenstates, we clearly show that the inversion density of any multilevel wavepacket of ammonia, including the case of perfectly aligned molecules, is symmetrically distributed between the two potential wells, at all times. This follows from a rigorous demonstration based on the evaluation of the expectation values of the inversion coordinate or equivalent projection operators. However, provided that these wavepackets involve inversion-rotation levels with opposite parity, the inversion density may exhibit dynamical spatial localization. In the latter case, the space-fixed inversion density or, equivalently, the expectation values of the projections of the inversion coordinate on the space-fixed axes, may oscillate between opposite directions in the space-fixed frame. Nevertheless, in all cases, localization of ammonia in a single potential well is impossible, even partially or transiently. This is equivalent to saying that the nitrogen atom has the same probability (one-half) to be on either side of the H-3 plane, for any wavepacket of the molecule and at all times-a conclusion which is in perfect accord with the principle of the indistinguishability of identical particles (nuclei).
Y1 - 2021
U6 - https://doi.org/10.1039/d1cp01991k
SN - 1463-9076
SN - 1463-9084
VL - 23
IS - 36
SP - 20509
EP - 20523
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Hermanns, Jolanda
A1 - Keller, David
T1 - How do preservice chemistry teachers rate tasks following the construct of school-related content knowledge in a concept-orientated course on organic chemistry?
JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2 - In this paper, we describe a study on tasks following the construct of school-related content knowledge. We know from previous studies that such tasks were rated by the preservice chemistry teachers as important for their future profession. Those studies were conducted in a traditional course on organic chemistry which was organized around chemical families. Therefore, we used and evaluated the tasks again in a new course on organic chemistry which is organized around basic concepts in organic chemistry. The results of this evaluation show that the students rate the tasks equally well but use other arguments for their rating. They do not focus only on the content of the tasks and whether this content belongs to the school curriculum or not. The students of the conceptual course rated the content more often (95%) as important for their future profession compared with the students in the traditional course (57%). Both groups of students rated the importance of the nature of the task the same way.
KW - Organic chemistry
KW - Second-Year undergraduate
KW - Alcohols
KW - Curriculum
KW - Molecular structure
KW - Organic structure
KW - Students
Y1 - 2021
U6 - https://doi.org/10.1021/acs.jchemed.1c00593
SN - 0021-9584
SN - 1938-1328
VL - 98
IS - 11
SP - 3442
EP - 3449
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Schwarze, Thomas
T1 - Determination of Pd2+ by fluorescence enhancement caused by an off-switching of an energy- and an electron transfer
JF - ChemistrySelect
N2 - In this paper, we introduce a fluorescent dye 1, which is able to detect selectively Pd2+ by a clear fluorescence enhancement (FE) in THF. In the presence of eight Pd2+ equivalents, we observed a fluorescence enhancement factor (FEF) of 28.3. The high Pd2+ induced FEF can be explained by an off switching of multiple quenching processes within 1 by Pd2+. In the free dye 1 a photoinduced electron transfer (PET) and energy transfer (ET) takes place and quenches the anthracenic fluorescence. The coordination of eight Pd2+ units by the alkylthio-substituted porphyrazine receptor suppresses the PET and ET quenching process and the anthracenic fluorescence is switched on.
KW - Palladium ion
KW - electron transfer
KW - energy transfer
KW - fluorescence
KW - porphyrazine
Y1 - 2021
U6 - https://doi.org/10.1002/slct.202003975
SN - 2365-6549
VL - 6
IS - 3
SP - 318
EP - 322
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Bedurke, Florian
A1 - Klamroth, Tillmann
A1 - Saalfrank, Peter
T1 - Many-electron dynamics in laser-driven molecules
BT - wavefunction theory vs. density functional theory
JF - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2 - With recent experimental advances in laser-driven electron dynamics in polyatomic molecules, the need arises for their reliable theoretical modelling. Among efficient, yet fairly accurate methods for many-electron dynamics are Time-Dependent Configuration Interaction Singles (TD-CIS) (a Wave Function Theory (WFT) method), and Real-Time Time-Dependent Density Functional Theory (RT-TD-DFT), respectively. Here we compare TD-CIS combined with extended Atomic Orbital (AO) bases, TD-CIS/AO, with RT-TD-DFT in a grid representation of the Kohn-Sham orbitals, RT-TD-DFT/Grid. Possible ionization losses are treated by complex absorbing potentials in energy space (for TD-CIS/AO) or real space (for RT-TD-DFT), respectively. The comparison is made for two test cases: (i) state-to-state transitions using resonant lasers (pi-pulses), i.e., bound electron motion, and (ii) large-amplitude electron motion leading to High Harmonic Generation (HHG). Test systems are a H-2 molecule and cis- and trans-1,2-dichlorethene, C2H2Cl2, (DCE). From time-dependent electronic energies, dipole moments and from HHG spectra, the following observations are made: first, for bound state-to-state transitions enforced by pi-pulses, TD-CIS nicely accounts for the expected population inversion in contrast to RT-TD-DFT, in agreement with earlier findings. Secondly, when using laser pulses under non-resonant conditions, dipole moments and lower harmonics in HHG spectra are obtained by TD-CIS/AO which are in good agreement with those obtained with RT-TD-DFT/Grid. Deviations become larger for higher harmonics and at low laser intensities, i.e., for low-intensity HHG signals. We also carefully test effects of basis sets for TD-CIS/AO and grid size for RT-TD-DFT/Grid, different exchange-correlation functionals in RT-TD-DFT, and absorbing boundaries. Finally, for the present examples, TD-CIS/AO is observed to be at least an order of magnitude more computationally efficient than RT-TD-DFT/Grid.
Y1 - 2021
U6 - https://doi.org/10.1039/d1cp01100f
SN - 1463-9076
SN - 1463-9084
VL - 23
IS - 24
SP - 13544
EP - 13560
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Fudickar, Werner
A1 - Metz, Melanie
A1 - Mai-Linde, Yasemin
A1 - Krüger, Tobias
A1 - Kelling, Alexandra
A1 - Sperlich, Eric
A1 - Linker, Torsten
T1 - Influence of functional groups on the ene reaction of singlet oxygen with 1,4-cyclohexadienes
JF - Photochemistry and photobiology : the official journal of the American Society for Photobiology
N2 - The photooxygenation of 1,4-cyclohexadienes has been studied with a special focus on regio- and stereoselectivities. In all examples, only the methyl-substituted double bond undergoes an ene reaction with singlet oxygen, to afford hydroperoxides in moderate to good yields. We explain the high regioselectivities by a "large-group effect" of the adjacent quaternary stereocenter. Nitriles decrease the reactivity of singlet oxygen, presumably by quenching, but can stabilize proposed per-epoxide intermediates by polar interactions resulting in different stereoselectivities. Spiro lactams and lactones show an interesting effect on regio- and stereoselectivities of the ene reactions. Thus, singlet oxygen attacks the double bond preferentially anti to the carbonyl group, affording only one regioisomeric hydroperoxide. If the reaction occurs from the opposite face, the other regioisomer is exclusively formed by severe electrostatic repulsion in a perepoxide intermediate. We explain this unusual behavior by the fixed geometry of spiro compounds and call it a "spiro effect" in singlet oxygen ene reactions.
Y1 - 2021
U6 - https://doi.org/10.1111/php.13422
SN - 0031-8655
SN - 1751-1097
VL - 97
IS - 6
SP - 1289
EP - 1297
PB - Wiley
CY - Malden, Mass.
ER -
TY - JOUR
A1 - Titov, Evgenii
A1 - Sharma, Anjali
A1 - Lomadze, Nino
A1 - Saalfrank, Peter
A1 - Santer, Svetlana
A1 - Bekir, Marek
T1 - Photoisomerization of an azobenzene-containing surfactant within a micelle
JF - ChemPhotoChem
N2 - Photosensitive azobenzene-containing surfactants have attracted great attention in past years because they offer a means to control soft-matter transformations with light. At concentrations higher than the critical micelle concentration (CMC), the surfactant molecules aggregate and form micelles, which leads to a slowdown of the photoinduced trans -> cis azobenzene isomerization. Here, we combine nonadiabatic dynamics simulations for the surfactant molecules embedded in the micelles with absorption spectroscopy measurements of micellar solutions to uncover the reasons responsible for the reaction slowdown. Our simulations reveal a decrease of isomerization quantum yields for molecules inside the micelles. We also observe a reduction of extinction coefficients upon micellization. These findings explain the deceleration of the trans -> cis switching in micelles of the azobenzene-containing surfactants.
KW - azobenzene
KW - micelles
KW - photoswitches
KW - rate constants
KW - surfactants
KW - surface hopping
Y1 - 2021
U6 - https://doi.org/10.1002/cptc.202100103
SN - 2367-0932
VL - 5
IS - 10
SP - 926
EP - 932
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Sinha, Shreya
A1 - Saalfrank, Peter
T1 - "Inverted" CO molecules on NaCl(100)
BT - a quantum mechanical study
JF - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2 - Somewhat surprisingly, inverted ("O-down") CO adsorbates on NaCl(100) were recently observed experimentally after infrared vibrational excitation (Lau et al., Science, 2020, 367, 175-178). Here we characterize these species using periodic density functional theory and a quantum mechanical description of vibrations. We determine stationary points and minimum energy paths for CO inversion, for low (1/8 and 1/4 monolayers (ML)) and high (1 ML) coverages. Transition state theory is applied to estimate thermal rates for "C-down" to "O-down" isomerization and the reverse process. For the 1/4 ML p(1 x 1) structure, two-dimensional and three-dimensional potential energy surfaces and corresponding anharmonic vibrational eigenstates obtained from the time-independent nuclear Schrodinger equation are presented. We find (i) rather coverage-independent CO inversion energies (of about 0.08 eV or 8 kJ mol(-1) per CO) and corresponding classical activation energies for "C-down" to "O-down" isomerization (of about 0.15 eV or 14 kJ mol(-1) per CO); (ii) thermal isomerization rates at 22 K which are vanishingly small for the "C-down" to "O-down" isomerization but non-negligible for the back reaction; (iii) several "accidentally degenerate" pairs of eigenstates well below the barrier, each pair describing "C-down" to "O-down" localized states.
Y1 - 2020
U6 - https://doi.org/10.1039/d0cp05198e
SN - 1463-9076
SN - 1463-9084
VL - 23
IS - 13
SP - 7860
EP - 7874
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Lüdecke, Nils
A1 - Schlaad, Helmut
T1 - Inspired by mussel adhesive protein
BT - hydrophilic cationic copoly(2-oxazoline)s carrying catecholic side chains
JF - Polymer Chemistry
N2 - A set of new functionalized poly(2-oxazoline) homopolymers and copolymers carrying protected catecholic side chains were prepared by microwave-assisted cationic ring-opening (co)polymerization. The copolymerizations of 2-ethyl-2-oxazoline with either 2-(3,4-dimethoxyphenyl)-, 2-(3,4-dimethoxybenzyl)-, or 2-(3,4-dimethoxycinnamyl)-2-oxazoline (comonomer ratio 90 : 10) produced gradient or random copolymers with narrow molar mass distributions. During the copolymerization with the 2-(3,4-dimethoxycinnamyl)-2-oxazoline, however, chain coupling reactions occurred at monomer conversions of >50%, supposedly via Michael-type addition of intermediately formed ketene N,O-acetal end groups to 3,4-dimethoxycinnamyl amide side chains. A poly[(2-ethyl-2-oxazoline)-grad-(2-(3,4-dimethoxyphenyl)-2-oxazoline)] was examplarily subjected to partial demethylation and acidic hydrolysis to give a hydrophilic copolymer carrying both catecholic and cationic units, which is designed as a bioinspired adhesive copolymer mimicking mussel adhesive protein.
Y1 - 2021
U6 - https://doi.org/10.1039/d1py00679g
SN - 1759-9962
VL - 12
IS - 37
SP - 5310
EP - 5319
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Schwarze, Thomas
A1 - Sperlich, Eric
A1 - Müller, Thomas
A1 - Kelling, Alexandra
A1 - Holdt, Hans-Jürgen
T1 - Synthesis efforts of acyclic bis(monoalkylamino)maleonitriles and macrocyclic bis(dialkylamino)maleonitriles as fluorescent probes for cations and a new colorimetric copper(II) chemodosimeter
JF - Helvetica chimica acta
N2 - In this article, we report on the synthesis of acyclic bis(monoalkylamino)maleonitriles and on the intended synthesis of macrocyclic bis(dialkylamino)maleonitriles to get fluorescent probes for cations. During our efforts to synthesize macrocyclic bis(dialkylamino)maleonitriles, we were only able to isolate macrocyclic bis(dialkylamino)-fumaronitriles. The synthesis of macrocyclic bis(dialkylamino)maleonitriles is challenging, due to the fact that bis-(dialkylamino)fumaronitriles are thermodynamically more stable than the corresponding bis(dialkylamino)-maleonitriles. Further, it turned out that the acyclic bis(monoalkylamino)maleonitriles and macrocyclic bis-(dialkylamino)fumaronitriles are no suitable tools to detect cations by a strong fluorescence enhancement. Further, only the bis(monoalkylamino)maleonitriles, which are bearing a 2-pyridyl unit as an additional complexing unit, are able to selectively recognize copper(II) by a color change from yellow to red.
KW - copper
KW - fumaronitrile
KW - ligands
KW - macrocycles
KW - maleonitrile
Y1 - 2021
U6 - https://doi.org/10.1002/hlca.202100028
SN - 1522-2675
VL - 104
IS - 6
SP - e2100028
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Fischer, Eric W.
A1 - Saalfrank, Peter
T1 - Ground state properties and infrared spectra of anharmonic vibrational polaritons of small molecules in cavities
JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2 - Recent experiments and theory suggest that ground state properties and reactivity of molecules can be modified when placed inside a nanoscale cavity, giving rise to strong coupling between vibrational modes and the quantized cavity field. This is commonly thought to be caused either by a cavity-distorted Born-Oppenheimer ground state potential or by the formation of light-matter hybrid states, vibrational polaritons. Here, we systematically study the effect of a cavity on ground state properties and infrared spectra of single molecules, considering vibration-cavity coupling strengths from zero up to the vibrational ultrastrong coupling regime. Using single-mode models for Li-H and O-H stretch modes and for the NH3 inversion mode, respectively, a single cavity mode in resonance with vibrational transitions is coupled to position-dependent molecular dipole functions. We address the influence of the cavity mode on polariton ground state energies, equilibrium bond lengths, dissociation energies, activation energies for isomerization, and on vibro-polaritonic infrared spectra. In agreement with earlier work, we observe all mentioned properties being strongly affected by the cavity, but only if the dipole self-energy contribution in the interaction Hamiltonian is neglected. When this term is included, these properties do not depend significantly on the coupling anymore. Vibro-polaritonic infrared spectra, in contrast, are always affected by the cavity mode due to the formation of excited vibrational polaritons. It is argued that the quantized nature of vibrational polaritons is key to not only interpreting molecular spectra in cavities but also understanding the experimentally observed modification of molecular reactivity in cavities.
Y1 - 2021
U6 - https://doi.org/10.1063/5.0040853
SN - 0021-9606
SN - 1089-7690
VL - 154
IS - 10
PB - American Institute of Physics
CY - Melville
ER -
TY - JOUR
A1 - Schwarze, Thomas
A1 - Kelling, Alexandra
A1 - Sperlich, Eric
A1 - Holdt, Hans-Jürgen
T1 - Influence of regioisomerism in 9-anthracenyl-substituted dithiodicyanoethene derivatives on photoinduced electron transfer controlled by intramolecular charge transfer
JF - ChemPhotoChem
N2 - In this paper, we report on the fluorescence behaviour of three regioisomers which consist of two 9-anthracenyl fluorophores and of differently substituted dithiodicyanoethene moieties. These isomeric fluorescent probes show different quantum yields (phi(f)). In these probes, an oxidative photoinduced electron transfer (PET) from the excited 9-anthracenyl fluorophore to the dithiodicyanoethene unit quenches the fluorescence. This quenching process is accelerated by an intramolecular charge transfer (ICT) of the push-pull pi-electron system of the dithiodicyanoethene group. The acceleration of the PET depends on the strength of the ICT unit. The higher the dipole moment of the ICT unit, the stronger the observed fluorescence quenching. To the best of our knowledge, this is the first report of a regioisomeric influence on an oxidative PET by an ICT.
KW - anthracene
KW - charge transfer
KW - electron transfer
KW - fluorescence
KW - isomerism
Y1 - 2021
U6 - https://doi.org/10.1002/cptc.202100070
SN - 2367-0932
VL - 5
IS - 10
SP - 911
EP - 914
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Fortes Martín, Rebeca
A1 - Prietzel, Claudia Christina
A1 - Koetz, Joachim
T1 - Template-mediated self-assembly of magnetite-gold nanoparticle superstructures at the water-oil interface of AOT reverse microemulsions
JF - Journal of colloid and interface science
N2 - Hypothesis: Bimetallic magnetite-gold nanostructures are interesting candidates to combine and enhance individual properties of each metal element in catalytic and analytical applications. Microemulsions have been employed in templated synthesis of nanoparticles, and their combination with different types of nanoparticles can further mediate interactions at the water-oil interface, providing new forms of hybrid nanostructures.
Experiments: Reverse water-in-oil microemulsions of droplet sizes below 50 nm were prepared from ternary mixtures of Aerosol-OT (AOT) as surfactant, incorporating 4 nm sized superparamagnetic nanoparticles (MNPs) to the hexane-pentanol oil phase and 5 nmsized polyethyleneimine-stabilized gold nanoparticles (Au(PEI)-NPs) to the water phase. The resulting isotropic L-2 phase, Winsor phases and organized nanostructures were investigated using conductometry, calorimetry, UV-Vis spectroscopy, cryoSEM and HRTEM.
Findings: Droplet-droplet interactions, morphology and surfactant film properties of AOT microemulsions could be modulated in different ways by the presence of the different nanoparticles from each liquid phase. Additionally, phase separation into Winsor phases allows the formation upon solvent evaporation of films with bimetallic heterostructures on the micrometer scale. This demonstrates a new way of nanoparticle templated assembly at liquid interfaces by assisted interactions between microemulsions and nanoparticles, as a promising strategy to obtain thin films of small, isotropic nanoparticles with hierarchical ordering.
KW - AOT
KW - Magnetite-gold nanoparticles
KW - Microemulsions
KW - Percolation
KW - Templated self-assembly
KW - Winsor phases
Y1 - 2021
U6 - https://doi.org/10.1016/j.jcis.2020.07.079
SN - 0021-9797
SN - 1095-7103
VL - 581
IS - Part A
SP - 44
EP - 55
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Dev, Akhil
A1 - Rösler, Alexander
A1 - Schlaad, Helmut
T1 - Limonene as a renewable unsaturated hydrocarbon solvent for living anionic polymerization of β-myrcene
JF - Polymer chemistry
N2 - The acyclic monoterpene beta-myrcene is polymerized by anionic polymerization at room temperature using sec-butyllithium as the initiator and the cyclic monoterpene DL-limonene as an unsaturated hydrocarbon solvent. The polymerization is a living process and allows production of polymyrcenes with narrow molar mass distribution ((sic) similar to 1.06) and high content of 1,4 units (similar to 90%) as well as block copolymers.
Y1 - 2021
U6 - https://doi.org/10.1039/d1py00570g
SN - 1759-9954
SN - 1759-9962
VL - 12
IS - 21
SP - 3084
EP - 3087
PB - Royal Society of Chemistry
CY - Cambridge
ER -