TY - JOUR A1 - Jain, Varun A1 - Wheeler, Joshua J. A1 - Ess, Daniel H. A1 - Noack, Sebastian A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut A1 - Bahr, Stephan A1 - Dietrich, Paul A1 - Meyer, Michael A1 - Thissen, Andreas A1 - Linford, Matthew R. T1 - Poly(gamma-benzyl l-glutamate), by near-ambient pressure XPS JF - Surface science spectra : SSS : an international journal & database devoted to archiving spectra from surfaces & interfaces N2 - 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. KW - near-ambient pressure x-ray photoelectron spectroscopy KW - NAP-XPS KW - XPS KW - polymer KW - poly(gamma-benzyl L-glutamate) KW - PBLG Y1 - 2019 U6 - https://doi.org/10.1116/1.5109121 SN - 1055-5269 SN - 1520-8575 VL - 26 IS - 2 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Patel, Dhananjay I. A1 - Noack, Sebastian A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut A1 - Bahr, Stephan A1 - Dietrich, Paul A1 - Meyer, Michael A1 - Thissen, Andreas A1 - Linford, Matthew R. T1 - Poly(L-lactic acid), by near-ambient pressure XPS JF - Surface Science Spectra N2 - 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. KW - near-ambient pressure X-ray photoelectron spectroscopy KW - NAP-XPS KW - XPS KW - Water Vapor Y1 - 2019 U6 - https://doi.org/10.1116/1.5110309 SN - 1055-5269 SN - 1520-8575 VL - 26 IS - 2 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Brosnan, Sarah M. A1 - Masic, Admir A1 - Schlaad, Helmut T1 - Fibrillar gels via the self-assembly of poly(L-glutamate)-based statistical copolymers JF - Polymer Chemistry N2 - 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. Y1 - 2015 U6 - https://doi.org/10.1039/c5py00491h SN - 1759-9954 SN - 1759-9962 VL - 6 IS - 28 SP - 5040 EP - 5052 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut T1 - Primary ammonium/tertiary amine-mediated controlled ring opening polymerisation of amino acid N-carboxyanhydrides JF - Chemical communications N2 - 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. Y1 - 2015 U6 - https://doi.org/10.1039/c5cc06905j SN - 1359-7345 SN - 1364-548X VL - 51 IS - 86 SP - 15645 EP - 15648 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut T1 - Controlled ring-opening polymerization of alpha-amino acid N-carboxyanhydrides in the presence of tertiary amines JF - Polymer : the international journal for the science and technology of polymers N2 - 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. KW - Ring-opening polymerization KW - Amino acid N-carboxyanhydride KW - NCA KW - Kinetics KW - Mechanism Y1 - 2017 U6 - https://doi.org/10.1016/j.polymer.2017.07.062 SN - 0032-3861 SN - 1873-2291 VL - 124 SP - 203 EP - 209 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Schopferer, Michael A1 - Schlaad, Helmut T1 - Physical Gelation of alpha-Helical Copolypeptides JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - 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. Y1 - 2016 U6 - https://doi.org/10.1021/acs.biomac.6b00427 SN - 1525-7797 SN - 1526-4602 VL - 17 SP - 2384 EP - 2391 PB - American Chemical Society CY - Washington ER -