@article{KutlugHassRecketal.2018, author = {Kutlug, Oezg{\"u}r and Hass, Roland and Reck, Stephan and Hartwig, Andreas}, title = {Inline characterization of dispersion formation of a solvent-borne acrylic copolymer by Photon Density Wave spectroscopy}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {556}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2018.08.011}, pages = {113 -- 119}, year = {2018}, abstract = {Most investigations on phase inversion (PI) of resins upon addition of water have been carried out by dynamic light scattering (DLS), torque, and viscosity measurements. The main problem, however, is analytic discontinuity due to sample removal and a changing matrix due to dilution during the preparation of the aqueous resin dispersions. This work presents Photon Density Wave (PDW) spectroscopy as a tool for the inline characterization of the acetone process for an acrylic copolymer with high acrylic acid (AA) content. PDW spectroscopy revealed different trends for optical properties compared to torque during water feed. Also the absence of PI due to dissolution of copolymer in the solvent/water mixture is observed by PDW spectroscopy. PI for the investigated copolymer did not occour during water feed but during removal of solvent. Different feeding rates of water gave similar trends while a change in temperature and degree of AA neutralization led to changes in optical properties and torque. Thermal processing showed that the optical properties of mixtures prior and after removal of solvent were completely different caused by changes of solubility.}, language = {en} } @article{BurekKrauseSchwotzeretal.2018, author = {Burek, Katja and Krause, Felix and Schwotzer, Matthias and Nefedov, Alexei and S{\"u}ssmuth, Julia and Haubitz, Toni and Kumke, Michael Uwe and Thissen, Peter}, title = {Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements}, series = {ACS sustainable chemistry \& engineering}, volume = {6}, journal = {ACS sustainable chemistry \& engineering}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.8b03244}, pages = {14669 -- 14678}, year = {2018}, abstract = {In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases.}, language = {en} } @article{HaenselBartaRietzeetal.2018, author = {H{\"a}nsel, Marc and Barta, Christoph and Rietze, Clemens and Utecht, Manuel Martin and Rueck-Braun, Karola and Saalfrank, Peter and Tegeder, Petra}, title = {Two-Dimensional Nonlinear Optical Switching Materials}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {122}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {44}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.8b08212}, pages = {25555 -- 25564}, year = {2018}, abstract = {Combining photochromism and nonlinear optical (NLO) properties of molecular switches-functionalized self-assembled monolayers (SAMs) represents a promising concept toward novel photonic and optoelectronic devices. Using second harmonic generation, density functional theory, and correlated wave function methods, we studied the switching abilities as well as the NLO contrasts between different molecular states of various fulgimide-containing SAMs on Si(111). Controlled variations of the linker systems as well as of the fulgimides enabled us to demonstrate very efficient reversible photoinduced ring-opening/closure reactions between the open and closed forms of the fulgimides. Thus, effective cross sections on the order of 10(-18) cm(-2) are observed. Moreover, the reversible switching is accompanied by pronounced NLO contrasts up to 32\%. Further molecular engineering of the photochromic switches and the linker systems may even increase the NLO contrast upon switching.}, language = {en} } @article{XiongWlodarczykSaalfrank2018, author = {Xiong, Tao and Wlodarczyk, Radoslaw and Saalfrank, Peter}, title = {Vibrationally resolved absorption and fluorescence spectra of perylene and N-substituted derivatives from autocorrelation function approaches}, series = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature}, volume = {515}, journal = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2018.06.011}, pages = {728 -- 736}, year = {2018}, abstract = {Vibrationally resolved absorption and emission (fluorescence) spectra of perylene and its N-derivatives in gas phase and in solution (acetonitrile) were simulated using a time-dependent approach based on correlation functions determined by density functional theory. By systematically varying the number and position of N atoms, it is shown that the presence of nitrogen heteroatoms has a negligible effect on the molecular structure and geometric distortions upon electronic transitions, while spectral properties change: in particular the number of N atoms is important while their position is less decisive. Thus, the N-substitution can be used to fine-tune the optical properties of perylene-based molecules.}, language = {en} } @article{UtechtGaebelKlamroth2018, author = {Utecht, Manuel Martin and Gaebel, Tina and Klamroth, Tillmann}, title = {Desorption induced by low energy charge carriers on Si(111)-7 x 7}, series = {Journal of computational chemistry : organic, inorganic, physical, biological}, volume = {39}, journal = {Journal of computational chemistry : organic, inorganic, physical, biological}, number = {30}, publisher = {Wiley}, address = {Hoboken}, issn = {0192-8651}, doi = {10.1002/jcc.25607}, pages = {2517 -- 2525}, year = {2018}, abstract = {We use clusters for the modeling of local ion resonances caused by low energy charge carriers in STM-induced desorption of benzene derivates from Si(111)-7 x 7. We perform Born-Oppenheimer molecular dynamics for the charged systems assuming vertical transitions to the charged states at zero temperature, to rationalize the low temperature activation energies, which are found in experiment for chlorobenzene. Our calculations suggest very similar low temperature activation energies for toluene and benzene. For the cationic resonance transitions to physisorption are found even at 0 K, while the anion remains chemisorbed during the propagations. Further, we also extend our previous static quantum chemical investigations to toluene and benzene. In addition, an in depth analysis of the ionization potentials and electron affinities, which are used to estimate resonance energies, is given.}, language = {en} } @article{TanLiuGlebeetal.2018, author = {Tan, Li and Liu, Bing and Glebe, Ulrich and B{\"o}ker, Alexander}, title = {Magnetic Field-Induced Assembly of Superparamagnetic Cobalt Nanoparticles on Substrates and at Liquid-Air Interface}, series = {Langmuir}, volume = {34}, journal = {Langmuir}, number = {46}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.8b02673}, pages = {13993 -- 14002}, year = {2018}, abstract = {Superparamagnetic cobalt nanoparticles (Co NPs) are an interesting material for self-assembly processes because of their magnetic properties. We investigated the magnetic field-induced assembly of superparamagnetic cobalt nanoparticles and compared three different approaches, namely, the assembly on solid substrates, at water-air, and ethylene glycol-air interfaces. Oleic acid- and trioctylphosphine oxide-coated Co NPs were synthesized via a thermolysis of cobalt carbonyl and dispersed into either hexane or toluene. The Co NP dispersion was dropped onto different substrates (e.g., transmission electron microscopy (TEM) grid, silicon wafer) and onto liquid surfaces. Transmission electron microscopy (TEM), scanning force microscopy, optical microscopy, as well as scanning electron microscopy showed that superparamagnetic Co NPs assembled into one-dimensional chains in an external magnetic field. By varying the concentration of the Co NP dispersion (1-5 mg/mL) and the strength of the magnetic field (4-54 mT), the morphology of the chains changed. Short, thin, and flexible chain structures were obtained at low NP concentration and low strength of magnetic field, whereas they became long, thick and straight when the NP concentration and the magnetic field strength increased. In comparison, the assembly of Co NPs from hexane dispersion at ethylene glycol-air interface showed the most regular and homogeneous alignment, since a more efficient spreading could be achieved on ethylene glycol than on water and solid substrates.}, language = {en} } @article{YalcinkayaBresselLindneretal.2018, author = {Yalcinkaya, Hacer and Bressel, Katharina and Lindner, Peter and Gradzielski, Michael}, title = {Controlled formation of vesicles with added styrene and their fixation by polymerization}, series = {Journal of colloid and interface science}, volume = {531}, journal = {Journal of colloid and interface science}, publisher = {Elsevier}, address = {San Diego}, issn = {0021-9797}, doi = {10.1016/j.jcis.2018.07.097}, pages = {672 -- 680}, year = {2018}, abstract = {Hypothesis: An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments: A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings: The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. (C) 2018 Elsevier Inc. All rights reserved.}, language = {en} } @article{PengBehlZhangetal.2018, author = {Peng, Xingzhou and Behl, Marc and Zhang, Pengfei and Mazurek-Budzynska, Magdalena and Feng, Yakai and Lendlein, Andreas}, title = {Synthesis of Well-Defined Dihydroxy Telechelics by (Co)polymerization of Morpholine-2,5-Diones Catalyzed by Sn(IV) Alkoxide}, series = {Macromolecular bioscience}, volume = {18}, journal = {Macromolecular bioscience}, number = {12}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-5187}, doi = {10.1002/mabi.201800257}, pages = {11}, year = {2018}, abstract = {Well-defined dihydroxy telechelic oligodepsipeptides (oDPs), which have a high application potential as building blocks for scaffold materials for tissue engineering applications or particulate carrier systems for drug delivery applications are synthesized by ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs) catalyzed by 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide). In contrast to ROP catalyzed by Sn(Oct)(2), the usage of Sn(IV) alkoxide leads to oDPs, with less side products and well-defined end groups, which is crucial for potential pharmaceutical applications. A slightly faster reaction of the ROP catalyzed by Sn(IV) alkoxide compared to the ROP initiated by Sn(Oct)(2)/EG is found. Copolymerization of different MDs resulted in amorphous copolymers with T(g)s between 44 and 54 degrees C depending on the molar comonomer ratios in the range from 25\% to 75\%. Based on the well-defined telechelic character of the Sn(IV) alkoxide synthesized oDPs as determined by matrix-assisted laser desorption/ionization time of flight measurements, they resemble interesting building blocks for subsequent postfunctionalization or multifunctional materials based on multiblock copolymer systems whereas the amorphous oDP-based copolymers are interesting building blocks for matrices of drug delivery systems.}, language = {en} } @article{HermannsSchmidt2018, author = {Hermanns, Jolanda and Schmidt, Bernd}, title = {Developing and Applying Stepped Supporting Tools in Organic Chemistry To Promote Students' Self-Regulated Learning}, series = {Journal of chemical education}, volume = {96}, journal = {Journal of chemical education}, number = {1}, publisher = {American Chemical Society}, address = {Washington}, issn = {0021-9584}, doi = {10.1021/acs.jchemed.8b00565}, pages = {47 -- 52}, year = {2018}, abstract = {Stepped supporting tools were developed and used in the university seminar Organic Chemistry taken by nonmajor chemistry students, which supported self-regulated learning. These supporting tools were also used for accompanying homework, which included a QR code that led to additional supporting tools. The application of stepped supporting tools in the seminars was evaluated by a four-item Likert scale. The students assessed the tools as a helpful instrument for solving tasks in chemistry.}, language = {en} } @article{NoackSchanzenbachKoetzetal.2018, author = {Noack, Sebastian and Schanzenbach, Dirk and Koetz, Joachim and Schlaad, Helmut}, title = {Polylactide-based amphiphilic block copolymers}, series = {Macromolecular rapid communications}, volume = {40}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201800639}, pages = {6}, year = {2018}, abstract = {The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures.}, language = {en} }