TY - JOUR A1 - Al-Naji, Majd A1 - Schlaad, Helmut A1 - Antonietti, Markus T1 - New (and old) monomers from biorefineries to make polymer chemistry more sustainable JF - Macromolecular rapid communications N2 - This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers. KW - biodegradable polymers KW - biorefineries KW - carbohydrate‐ based KW - monomers KW - green polymers KW - lignocellulosic biomass Y1 - 2020 U6 - https://doi.org/10.1002/marc.202000485 SN - 1022-1336 SN - 1521-3927 VL - 42 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Behrendt, Felix Nicolas A1 - Hess, Andreas A1 - Lehmann, Max A1 - Schmidt, Bernd A1 - Schlaad, Helmut T1 - Polymerization of cystine-derived monomers JF - Polymer Chemistry N2 - Cystine was used as a platform chemical to prepare cyclic and acyclic monomers for entropy-driven ringopening polymerization (ED-ROMP) via olefin or disulfide metathesis and for step-growth polymerization. The olefin ED-ROMP of an olefin/disulfide containing 16-atom macrocycle using the 3rd generation Grubbs catalyst was examined in greater detail. Kinetic studies revealed that the catalyst turned inactive during the polymerization, which limited the achievable (apparent) polymer molar mass to similar to 70 kg mol(-1). Such limitation could be overcome with the disulfide ED-ROMP of the same macrocycle to yield polymers with molar masses of up to 180 kg mol(-1). The step-growth polymerizations of acyclic diene and dithiol monomers via olefin metathesis or oxidation were far less effective and yielded just low molar mass polymers or oligomers; photopolymerization of a thiol-ene monomer produced a polyester with a molar mass of 35 kg mol(-1). Y1 - 2019 U6 - https://doi.org/10.1039/c9py00118b SN - 1759-9954 SN - 1759-9962 VL - 10 IS - 13 SP - 1636 EP - 1641 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Behrendt, Felix Nicolas A1 - Schlaad, Helmut T1 - Entropy-Driven Ring-Opening Disulfide Metathesis Polymerization for the Synthesis of Functional Poly(disulfide)s JF - Macromolecular rapid communications N2 - Metal-free entropy-driven disulfide metathesis polymerization of unsaturated L-cystine based macrocycles produces high-molar-mass heterofunctional poly(disulfide)s, i.e., poly(ester-disulfide-alkene) and poly(amide-disulfide-alkene); M-w(app) = 44-60 kDa, (sic) > 1.7. The polymerization is fast and reaches equilibrium within 1-5 minutes (monomer conversion 70-90%) in polar aprotic solvents such as N,N-dimethylacetamide, dimethylsulfoxide, or y-valerolactone. Thiol-terminated polymers are stable in bulk or when dissolved in weakly polar solvents, but rapidly depolymerize in dilute polar solution. KW - disulfide KW - macrocycles KW - metathesis KW - ring-opening polymerization Y1 - 2018 U6 - https://doi.org/10.1002/marc.201700735 SN - 1022-1336 SN - 1521-3927 VL - 39 IS - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Behrendt, Felix Nicolas A1 - Schlaad, Helmut T1 - Metathesis polymerization of cystine-based macrocycles JF - Polymer Chemistry N2 - Macrocycles based on L-cystine were synthesized by ring-closing metathesis (RCM) and subsequently polymerized by entropy-driven ring-opening metathesis polymerization (ED-ROMP). Monomer conversion reached similar to 80% in equilibrium and the produced poly (ester-amine-disulfide-alkene)s exhibited apparent molar masses (M-w(app)) of up to 80 kDa and dispersities (D) of similar to 2. The polymers can be further functionalized with acid anhydrides and degraded by reductive cleavage of the main-chain disulfide. Y1 - 2016 U6 - https://doi.org/10.1039/c6py01864e SN - 1759-9954 SN - 1759-9962 VL - 8 IS - 2 SP - 366 EP - 369 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bogomolova, Anna A1 - Secker, Christian A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-induced multistep assembly of double-hydrophilic block copolypeptoids in water JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - The aqueous solution behavior of thermoresponsive-hydrophilic block copolypeptoids, i.e., poly(N-(n-propyl)glycine) (x) -block-poly(N-methylglycine) (y) (x = 70; y = 23, 42, 76), in the temperature range of 20-45 A degrees C is studied. Turbidimetric analyses of the 0.1 wt% aqueous solutions reveal two cloud points at T (cp)similar to 30 and 45 A degrees C and a clearing point in between at T (cl)similar to 42 A degrees C. Temperature-dependent dynamic light scattering (DLS) suggest that right above the first collapse temperature, single polymer molecules assemble into large structures which upon further heating, i.e., at the clearing point temperature, disassemble into micelle-like structures. Upon further heating, the aggregates start to grow again in size, as recognized by the second cloud point, through a crystallization process. KW - Polypeptoids KW - Block copolymers KW - Thermoresponsive KW - Self-assembly Y1 - 2017 U6 - https://doi.org/10.1007/s00396-017-4044-6 SN - 0303-402X SN - 1435-1536 VL - 295 SP - 1305 EP - 1312 PB - Springer CY - New York ER - TY - JOUR A1 - Brosnan, Sarah M. A1 - Schlaad, Helmut T1 - Modification of polypeptide materials by Thiol-X chemistry JF - Polymer : the international journal for the science and technology of polymers N2 - Thiol-X chemistry has proven to be a valuable toolbox for modification of peptides, proteins, monomers, and polymers. Recently, this has become especially true for the modification of polypeptides (monomers or polymers), which has resulted in a plethora of novel polymers and materials. With this in mind, this highlight focuses on the recent literature concerning the modification of polypeptides by the use of thiol-X chemistry, in particular to synthetic polypeptides either at the monomer or polymer stage modified by thiol-ene, -Michael addition, and -yne chemistries. (C) 2014 Published by Elsevier Ltd. KW - Polypeptide KW - Thiol-X KW - Click chemistry Y1 - 2014 U6 - https://doi.org/10.1016/j.polymer.2014.08.067 SN - 0032-3861 SN - 1873-2291 VL - 55 IS - 22 SP - 5511 EP - 5516 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Brosnan, Sarah M. A1 - Schlaad, Helmut A1 - Antonietti, Markus T1 - Aqueous Self-Assembly of Purely Hydrophilic Block Copolymers into Giant Vesicles JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Self-assembly of macromolecules is fundamental to life itself, and historically, these systems have been primitively mimicked by the development of amphiphilic systems, driven by the hydrophobic effect. Herein, we demonstrate that self-assembly of purely hydrophilic systems can be readily achieved with similar ease and success. We have synthesized double hydrophilic block copolymers from polysaccharides and poly(ethylene oxide) or poly(sarcosine) to yield high molar mass diblock copolymers through oxime chemistry. These hydrophilic materials can easily assemble into nanosized (<500nm) and microsized (>5m) polymeric vesicles depending on concentration and diblock composition. Because of the solely hydrophilic nature of these materials, we expect them to be extraordinarily water permeable systems that would be well suited for use as cellular mimics. KW - block copolymers KW - polymersomes KW - polysaccharides KW - self-assembly KW - vesicles Y1 - 2015 U6 - https://doi.org/10.1002/anie.201502100 SN - 1433-7851 SN - 1521-3773 VL - 54 IS - 33 SP - 9715 EP - 9718 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Casse, Olivier A1 - Shkilnyy, Andriy A1 - Linders, Jürgen A1 - Mayer, Christian A1 - Häussinger, Daniel A1 - Völkel, Antje A1 - Thünemann, Andreas F. A1 - Dimova, Rumiana A1 - Cölfen, Helmut A1 - Meier, Wolfgang P. A1 - Schlaad, Helmut A1 - Taubert, Andreas T1 - Solution behavior of double-hydrophilic block copolymers in dilute aqueous solution JF - Macromolecules : a publication of the American Chemical Society N2 - The self-assembly of double-hydrophilic poly(ethylene oxide)-poly(2-methyl-2-oxazoline) diblock copolymers in water has been studied. Isothermal titration calorimetry, small-angle X-ray scattering, and analytical ultracentrifugation suggest that only single polymer chains are present in solution. In contrast, light scattering and transmission electron microscopy detect aggregates with radii of ca. 100 nm. Pulsed field gradient NMR spectroscopy confirms the presence of aggregates, although only 2% of the polymer chains undergo aggregation. Water uptake experiments indicate differences in the hydrophilicity of the two blocks, which is believed to be the origin of the unexpected aggregation behavior (in accordance with an earlier study by Ke et al. [Macromolecules 2009, 42, 5339-5344]). The data therefore suggest that even in double-hydrophilic block copolymers, differences in hydrophilicity are sufficient to drive polymer aggregation, a phenomenon that has largely been overlooked or ignored so far. Y1 - 2012 U6 - https://doi.org/10.1021/ma300621g SN - 0024-9297 VL - 45 IS - 11 SP - 4772 EP - 4777 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Chandran, Sivasurender A1 - Dold, Stefanie A1 - Buvignier, Amaury A1 - Krannig, Kai-Steffen A1 - Schlaad, Helmut A1 - Reiter, Günter A1 - Reiter, Renate T1 - Tuning Morphologies of Langmuir Polymer Films Through Controlled Relaxations of Non-Equilibrium States JF - Langmuir N2 - Langmuir polymers films (LPFs) frequently form non-equilibrium states which are manifested in a decay of the surface pressure with time when the system is allowed to relax. Monitoring and manipulating the temporal evolution of these relaxations experimentally helps to shed light on the associated molecular reorganization processes. We present a systematic study based on different compression protocols and show how these reorganization processes impact the morphology of LPFs of poly(gamma-benzyl-L-glutamate) (PBLG); visualized by means of atomic force microscopy. Upon continuous compression, a fibrillar morphology was formed with a surface decorated by squeezed-out islands. By contrast, stepwise compression promoted the formation of a fibrillar network with a bimodal distribution of fibril diameters, caused by merging of fibrils. Finally, isobaric compression induced in-plane compaction of the monolayer. We correlate these morphological observations with the kinetics of the corresponding relaxations, described best by a sum of two exponential functions with different time scales representing two molecular processes. We discuss the observed kinetics and the resulting morphologies in the context of nucleation and growth, characteristic for first-order phase transitions. Our results demonstrate that the preparation conditions of LPFs have tremendous impact on ordering of the molecules and hence various macroscopic properties of such films. Y1 - 2015 U6 - https://doi.org/10.1021/acs.langmuir.5b01212 SN - 0743-7463 VL - 31 IS - 23 SP - 6426 EP - 6435 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Chen, Ye A1 - Song, Qilei A1 - Zhao, Junpeng A1 - Gong, Xiangjun A1 - Schlaad, Helmut A1 - Zhang, Guangzhao T1 - Betulin-Constituted multiblock amphiphiles for broad-spectrum protein resistance JF - ACS applied materials & interfaces N2 - Multiblock-like amphiphilic polyurethanes constituted by poly(ethylene oxide) and biosourced betulin are designed for antifouling and synthesized by a convenient organocatalytic route comprising tandem chain-growth and step-growth polymerizations. The doping density of betulin (D-B) in the polymer chain structure is readily varied by a mixed-initiator strategy. The spin-coated polymer films exhibit unique nanophase separation and protein resistance behaviors. Higher D-B leads to enhanced surface hydrophobicity and, unexpectedly, improved protein resistance. It is found that the surface holds molecular-level heterogeneity when D-B is substantially high due to restricted phase separation; therefore, broad-spectrum protein resistance is achieved despite considerable surface hydrophobicity. As D-B decreases, the distance between adjacent betulin units increases so that hydrophobic nanodomains are formed, which provide enough landing areas for relatively small-sized proteins to adsorb on the surface. KW - amphiphilic surface KW - antifouling KW - multiblock copolymer KW - organocatalytic polymerization KW - renewable resource Y1 - 2018 U6 - https://doi.org/10.1021/acsami.7b16255 SN - 1944-8244 VL - 10 IS - 7 SP - 6593 EP - 6600 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Dani, Alessandro A1 - Tauber, Karoline A1 - Zhang, Weiyi A1 - Schlaad, Helmut A1 - Yuan, Jiayin T1 - Stable Covalently Photo-Crosslinked Poly(Ionic Liquid) Membrane with Gradient Pore Size JF - Macromolecular rapid communications N2 - Porous polyelectrolyte membranes stable in a highly ionic environment are obtained by covalent crosslinking of an imidazolium-based poly(ionic liquid). The crosslinking reaction involves the UV light-induced thiol-ene (click) chemistry, and the phase separation, occurring during the crosslinking step, generates a fully interconnected porous structure in the membrane. The porosity is on the order of the micrometer scale and the membrane shows a gradient of pore size across the membrane cross-section. The membrane can separate polystyrene latex particles of different size and undergoes actuation in contact with acetone due to the asymmetric porous structure. KW - membrane KW - photo-crosslinked KW - poly(ionic liquid) KW - porous structure Y1 - 2017 U6 - https://doi.org/10.1002/marc.201700167 SN - 1022-1336 SN - 1521-3927 VL - 38 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Das, Abhijna A1 - El-Tawargy, Ahmed S. A1 - Khechine, Emna A1 - Noack, Sebastian A1 - Schlaad, Helmut A1 - Reiter, Günter A1 - Reiter, Renate T1 - Controlling Nucleation in Quasi-Two-Dimensional Langmuir Poly(L-lactide) Films through Variation of the Rate of Compression JF - Langmuir N2 - We studied morphological changes in a quasi-two-dimensional Langmuir film of low molar mass poly(L-lactide) upon increasing the surface density, starting from randomly distributed molecules to a homogeneous monolayer of closely packed molecules, followed by nucleation and growth of mesoscopic, three-dimensional clusters from an overcompressed monolayer. The corresponding nucleation density of mesoscopic clusters within the monolayer can be tailored through variation of the rate of compression. For a given surface density and temperature, the nucleation probability was found to increase linearly with the rate of compression, allowing to adjust the density of mesoscopic clusters over nearly 2 orders magnitude. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b00619 SN - 0743-7463 VL - 35 IS - 18 SP - 6129 EP - 6136 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Das, Abhijna A1 - Noack, Sebastian A1 - Schlaad, Helmut A1 - Reiter, Günter A1 - Reiter, Renate T1 - Exploring pathways to equilibrate Langmuir polymer films JF - Langmuir N2 - Focusing on the phase-coexistence region in Langmuir films of poly(L-lactide), we investigated changes in nonequilibrated morphologies and the corresponding features of the isotherms induced by different experimental pathways of lateral compression and expansion. In this coexistence region, the surface pressure II was larger than the expected equilibrium value and was found to increase upon compression, i.e., exhibited a nonhorizontal plateau. As shown earlier by using microscopic techniques [Langmuir 2019, 35, 6129-6136], in this plateau region, well-ordered mesoscopic clusters coexisted with a surrounding matrix phase. We succeeded in reducing Pi either by slowing down the rate of compression or through increasing the waiting time after stopping the movement of the barriers, which allowed for relaxations in the coexistence region. Intriguingly, the most significant pressure reduction was observed when recompressing a film that had already been compressed and expanded, if the recompression was started from an area value smaller than the one anticipated for the onset of the coexistence region. This observation suggests a "self-seeding" behavior, i.e., pre-existing nuclei allowed to circumvent the nucleation step. The decrease in Pi was accompanied by a transformation of the initially formed metastable mesoscopic clusters into a thermodynamically favored filamentary morphology. Our results demonstrate that it is practically impossible to obtain fully equilibrated coexisting phases in a Langmuir polymer film, neither under conditions of extremely slow continuous compression nor for long waiting times at a constant area in the coexistence region which allow for reorganization. Y1 - 2020 U6 - https://doi.org/10.1021/acs.langmuir.0c01268 SN - 0743-7463 VL - 36 IS - 28 SP - 8184 EP - 8192 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Debsharma, Tapas A1 - Behrendt, Felix Nicolas A1 - Laschewsky, Andre A1 - Schlaad, Helmut T1 - Ring-opening metathesis polymerization of biomass-derived levoglucosenol JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker N2 - The readily available cellulose-derived bicyclic compound levoglucosenol was polymerized through ring-opening metathesis polymerization (ROMP) to yield polylevoglucosenol as a novel type of biomass-derived thermoplastic polyacetal, which, unlike polysaccharides, contains cyclic as well as linear segments in its main chain. High-molar-mass polyacetals with apparent weight-average molar masses of up to 100kgmol(-1) and dispersities of approximately 2 were produced despite the non-living/controlled character of the polymerization due to irreversible deactivation or termination of the catalyst/active chain ends. The resulting highly functionalized polyacetals are glassy in bulk with a glass transition temperature of around 100 degrees C. In analogy to polysaccharides, polylevoglucosenol degrades slowly in an acidic environment. KW - degradable polymers KW - metathesis KW - ring-opening polymerization KW - sustainable chemistry KW - thermoplastics Y1 - 2019 U6 - https://doi.org/10.1002/anie.201814501 SN - 1433-7851 SN - 1521-3773 VL - 58 IS - 20 SP - 6718 EP - 6721 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 - Demirel, A. Levent A1 - Guner, Pinar Tatar A1 - Verbraeken, Bart A1 - Schlaad, Helmut A1 - Schubert, Ulrich S. A1 - Hoogenboom, Richard T1 - Revisiting the Crystallization of Poly(2-alkyl-2-oxazoline)s JF - Journal of polymer science : B, Polymer physics N2 - Poly(2-alkyl-2-oxazoline)s (PAOx) exhibit different crystallization behavior depending on the length of the alkyl side chain. PAOx having methyl, ethyl, or propyl side chains do not show any bulk crystallization. Crystallization in the heating cycle, that is, cold crystallization, is observed for PAOx with butyl and pentyl side chains. For PAOx with longer alkyl side chains crystallization occurs in the cooling cycle. The different crystallization behavior is attributed to the different polymer chain mobility in line with the glass transition temperature (T-g) dependency on alkyl side chain length. The decrease in chain mobility with decreasing alkyl side chain length hinders the relaxation of the polymer backbone to the thermodynamic equilibrium crystalline structure. Double melting behavior is observed for PButOx and PiPropOx which is explained by the melt-recrystallization mechanism. Isothermal crystallization experiments of PButOx between 60 and 90 degrees C and PiPropOx between 90 and 150 degrees C show that PAOx can crystallize in bulk when enough time is given. The decrease of Tg and the corresponding increase in chain mobility at T > T-g with increasing alkyl side chain length can be attributed to an increasing distance between the polymer backbones and thus decreasing average strength of amide dipole interactions. (C) 2015 Wiley Periodicals, Inc. KW - chain mobility KW - crystallization KW - differential scanning calorimetry (DSC) KW - effect of alkyl side chains KW - glass transition temperature KW - melt KW - melt-recrystallization KW - polymer crystallization Y1 - 2016 U6 - https://doi.org/10.1002/polb.23967 SN - 0887-6266 SN - 1099-0488 VL - 54 SP - 721 EP - 729 PB - Wiley-Blackwell CY - Hoboken 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 - TY - JOUR A1 - Diehl, Christina A1 - Cernoch, Peter A1 - Zenke, Ingrid A1 - Runge, Heike A1 - Pitschke, Rona A1 - Hartmann, Juergen A1 - Tiersch, Brigitte A1 - Schlaad, Helmut T1 - Mechanistic study of the phase separation/crystallization process of poly(2-isopropyl-2-oxazoline) in hot water N2 - The kinetics of the crystallization of thermoresponsive poly(2-isopropyl-2-oxazoline) in water and the time- dependent evolution of the morphology were examined using wide-angle X-ray scattering and conventional and cryogenic scanning electron microscopy. Results indicate that a temperature-induced phase separation produces a bicontinuous polymer network-like structure, which with the onset of crystallization collapses into individual particles (1-2 mu m in diameter) composed of a porous fiber mesh. Nanofibers then preferentially form at the particle surface, thus wrapping the microspheres like a ball of wool. The particle morphology is severely affected by changes in temperature and less by the initial polymer concentration. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/sm/index.asp U6 - https://doi.org/10.1039/C0sm00114g SN - 1744-683X ER - TY - JOUR A1 - Diehn, Sabrina Maria A1 - Schlaad, Helmut A1 - Kneipp, Janina T1 - Multivariate imaging for fast evaluation of in situ dark field microscopy hyperspectral data JF - Molecules : a journal of synthetic chemistry and natural product chemistry N2 - Dark field scattering microscopy can create large hyperspectral data sets that contain a wealth of information on the properties and the molecular environment of noble metal nanoparticles. For a quick screening of samples of microscopic dimensions that contain many different types of plasmonic nanostructures, we propose a multivariate analysis of data sets of thousands to several hundreds of thousands of scattering spectra. By using non-negative matrix factorization for decomposing the spectra, components are identified that represent individual plasmon resonances and relative contributions of these resonances to particular microscopic focal volumes in the mapping data sets. Using data from silver and gold nanoparticles in the presence of different molecules, including gold nanoparticle-protein agglomerates or silver nanoparticles forming aggregates in the presence of acrylamide, plasmonic properties are observed that differ from those of the original nanoparticles. For the case of acrylamide, we show that the plasmon resonances of the silver nanoparticles are ideally suited to support surface enhanced Raman scattering (SERS) and the two-photon excited process of surface enhanced hyper Raman scattering (SEHRS). Both vibrational tools give complementary information on the in situ formed polyacrylamide and the molecular composition at the nanoparticle surface. KW - localized surface plasmon resonances KW - gold nanoparticles KW - silver nanoparticles KW - dark field microscopy KW - acrylamide KW - hyperspectral imaging KW - non-negative matrix factorization KW - surface-enhanced Raman scattering (SERS) KW - surface-enhanced hyper Raman scattering (SEHRS) Y1 - 2022 U6 - https://doi.org/10.3390/molecules27165146 SN - 1420-3049 VL - 27 IS - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Doriti, Afroditi A1 - Brosnan, Sarah M. A1 - Weidner, Steffen M. A1 - Schlaad, Helmut T1 - Synthesis of polysarcosine from air and moisture stable N-phenoxycarbonyl-N-methylglycine assisted by tertiary amine base JF - Polymer Chemistry N2 - Polysarcosine (M-n = 3650-20 000 g mol(-1), D similar to 1.1) was synthesized from the air and moisture stable N-phenoxycarbonyl-N-methylglycine. Polymerization was achieved by in situ transformation of the urethane precursor into the corresponding N-methylglycine-N-carboxyanhydride, when in the presence of a non-nucleophilic tertiary amine base and a primary amine initiator. Y1 - 2016 U6 - https://doi.org/10.1039/c6py00221h SN - 1759-9954 SN - 1759-9962 VL - 7 SP - 3067 EP - 3070 PB - Royal Society of Chemistry CY - Cambridge ER -