Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-39339 Wissenschaftlicher Artikel Vacogne, Charlotte D.; Brosnan, Sarah M.; Masic, Admir; Schlaad, Helmut Fibrillar gels via the self-assembly of poly(L-glutamate)-based statistical copolymers Polypeptides having secondary structures often undergo self-assembly which can extend over multiple length scales. Poly(gamma-benzyl-L-glutamate) (PBLG), for example, folds into a-helices and forms physical organogels, whereas poly(L-glutamic acid) (PLGA at acidic pH) or poly(L-glutamate) (PLG at neutral/basic pH) do not form hydrogels. We explored the gelation of modified PBLG and investigated the deprotection of the carboxylic acid moieties in such gels to yield unique hydrogels. This was accomplished through photo-crosslinking gelation of poly(gamma-benzyl-L-glutamate-co-allylglycine) statistical copolymers in toluene, tetrahydrofuran, and 1,4-dioxane. Unlike most polymer-based chemical gels, our gels were prepared from dilute solutions (<20 g L-1, i.e., <2% w/v) of low molar mass polymers. Despite such low concentrations and molar masses, our dioxane gels showed high mechanical stability and little shrinkage; remarkably, they also exhibited a porous fibrillar network. Deprotection of the carboxylic acid moieties in dioxane gels yielded pH responsive and highly absorbent PLGA/PLG-based hydrogels (swelling ratio of up to 87), while preserving the network structure, which is an unprecedented feature in the context of crosslinked PLGA gels. These outstanding properties are highly attractive for biomedical materials. Cambridge Royal Society of Chemistry 2015 13 Polymer Chemistry 6 28 5040 5052 10.1039/c5py00491h Institut für Chemie OPUS4-39297 Wissenschaftlicher Artikel Vacogne, Charlotte D.; Schlaad, Helmut Primary ammonium/tertiary amine-mediated controlled ring opening polymerisation of amino acid N-carboxyanhydrides Stable commercial primary ammonium chlorides were combined with tertiary amines to initiate the controlled ring opening polymerisation of amino acid N-carboxyanhydrides to yield polypeptides with defined end group structure, predetermined molar mass and narrow molar mass distribution. Cambridge Royal Society of Chemistry 2015 4 Chemical communications 51 86 15645 15648 10.1039/c5cc06905j Institut für Chemie OPUS4-45188 Wissenschaftlicher Artikel Vacogne, Charlotte D.; Schopferer, Michael; Schlaad, Helmut Physical Gelation of alpha-Helical Copolypeptides Owing to its rod-like alpha-helical secondary structure, the synthetic polypeptide poly(gamma-benzyl-L-glutamate) (PBLG) can form physical and thermoreversible gels in helicogenic solvents such as toluene. The versatility of PBLG can be increased by introducing functionalizable comonomers, such as allylglycine (AG). In this work we examined the secondary structure of PBLG and a series of statistical poly(gamma-benzyl-L-glutamate-co-allylglycine) copolypeptides, varying in composition and chain length, by circular dichroism (CD), Fourier-transform infrared (FTIR) and Raman spectroscopy, and wide-angle X-ray scattering (WAXS). The secondary structure of PBLG and the copolypeptides presented dissimilarities that increased with increasing AG molar fraction, especially when racemic AG units were incorporated. The physical gelation behavior of these copolypeptides was analyzed by temperature-sweep H-1 NMR and rheological measurements. The study revealed that both copolypeptide composition and chain length affected secondary structure, gelation temperature, and gel stiffness. Washington American Chemical Society 2016 8 Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences 17 2384 2391 10.1021/acs.biomac.6b00427 Institut für Chemie OPUS4-46424 Wissenschaftlicher Artikel Vacogne, Charlotte D.; Schlaad, Helmut Controlled ring-opening polymerization of alpha-amino acid N-carboxyanhydrides in the presence of tertiary amines The mechanism of the primary ammonium/tertiary amine-mediated ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) was investigated. Kinetic analyses revealed that the normal amine mechanism (NAM) together with a dormant-active chain end equilibrium were responsible for the controlled nature of this polymerization pathway, but that the polymerization also proceeded via the activated monomer mechanism (AMM). Mixtures of primary amines (1 equiv) and tertiary amines (0-1.5 equiv) were therefore tested to confirm the co-existence of the NAM and AMM and determine the limits for a controlled polymerization. For tertiary amine molar fractions smaller than 0.8 equiv, the reaction times were greatly reduced (compared to primary amine-initiated polymerization) without compromising the control of the reaction. Hence, the polymerization of NCA can proceed in a controlled manner even when the AMM contributes to the overall chain growth mechanism. (C) 2017 Elsevier Ltd. All rights reserved. Oxford Elsevier 2017 7 Polymer : the international journal for the science and technology of polymers 124 203 209 10.1016/j.polymer.2017.07.062 Institut für Chemie OPUS4-47672 Wissenschaftlicher Artikel Jain, Varun; Wheeler, Joshua J.; Ess, Daniel H.; Noack, Sebastian; Vacogne, Charlotte D.; Schlaad, Helmut; Bahr, Stephan; Dietrich, Paul; Meyer, Michael; Thissen, Andreas; Linford, Matthew R. Poly(gamma-benzyl l-glutamate), by near-ambient pressure XPS Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i. e., at greater than 2500 Pa. In this study, poly(.- benzyl L- glutamate) (PBLG) with a molar mass of 11.3 kg/mol was analyzed by NAP-XPS; here, we show the survey, C 1s, N 1s, and O 1s narrow scans of PBLG. The C 1s peak envelope was fitted in three different ways, to five, six, or seven synthetic peaks. In each fit, there was also a shake-up signal. The O 1s narrow scan was well fit with three peaks: CZO and CvO in a 1:2 ratio from the polymer, and a higher energy signal from water vapor. Hartree-Fock orbital energies of a model monomer served as a guide to an additional fit of the C 1s envelope. Melville American Institute of Physics 2019 10 Surface science spectra : SSS : an international journal & database devoted to archiving spectra from surfaces & interfaces 26 2 10.1116/1.5109121 Institut für Physik und Astronomie OPUS4-47787 Wissenschaftlicher Artikel Patel, Dhananjay I.; Noack, Sebastian; Vacogne, Charlotte D.; Schlaad, Helmut; Bahr, Stephan; Dietrich, Paul; Meyer, Michael; Thissen, Andreas; Linford, Matthew R. Poly(L-lactic acid), by near-ambient pressure XPS Near ambient pressure - x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at 2500Pa or higher. With NAP-XPS, one can analyze moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission we show C 1s, O 1s, and survey NAP-XPS spectra from poly(L-lactic acid). The C 1s and O 1s envelopes were fit with three and two Gaussian-Lorentzian sum functions, respectively. Water vapor (800Pa) was used as the residual gas for charge compensation, which was confirmed by the sharp peak at 535.0 eV in the O 1s narrow scan. The uniqueness plot corresponding to the C 1s fit shows that the fit parameters had statistical significance. C 1s and O 1s spectra of PLLA damaged by exposure to x-rays for ca. 1 hour are also included. Published by the AVS. Melville American Institute of Physics 2019 8 Surface Science Spectra 26 2 10.1116/1.5110309 Institut für Physik und Astronomie