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941.
Effects of aromatic regularity on the structure and conductivity of polyimide‐poly(ethylene glycol) materials doped with ionic liquid
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Elyse Coletta Michael F. Toney Curtis W. Frank 《Journal of Polymer Science.Polymer Physics》2015,53(7):509-521
An understanding of the structure and properties of polymer electrolyte systems can be crucial to a variety of different applications. The current work performs a study of the composition, structure and properties of poly(ethylene glycol) (PEG)‐aromatic polyimide systems incorporating ionic liquids that are relevant to several applications especially fuel cell membranes. Composition was varied through using different aromatic dianhydrides, aromatic diamines and in some cases synthesis solvent. Properties were characterized using Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, small‐angle x‐ray scattering, electrochemical impedance spectroscopy and cyclic voltammetry. By varying solvent, aromatic regularity and expected rigidity can be tuned, impacting average conductivity by 30%. Varying the aromatic diamine can influence the length scale and amount of aromatic regularity, which can ultimately affect the conductivity by a factor of four. The maximum conductivity reached was 83 mS/cm at 80 °C and 70 %RH. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 509–521 相似文献
942.
Dr. James Jennings Dr. Erik J. Cornel Dr. Matthew J. Derry Dr. Deborah L. Beattie Dr. Matthew J. Rymaruk Oliver J. Deane Prof. Anthony J. Ryan Prof. Steven P. Armes 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10940-10945
Polymerization-induced self-assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so-called “high χ–low N” diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub-10 nm surface features. By varying the degree of polymerization of the stabilizer and core-forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre-organization of copolymer chains within sterically-stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution-cast molecularly-dissolved copolymer chains. 相似文献
943.
Dr. Jin Lu Hesam Mazidi Tianben Ding Oumeng Zhang Prof. Matthew D. Lew 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17725-17732
In soft matter, thermal energy causes molecules to continuously translate and rotate, even in crowded environments, thereby impacting the spatial organization and function of most molecular assemblies, such as lipid membranes. Directly measuring the orientation and spatial organization of large collections (>3000 molecules μm−2) of single molecules with nanoscale resolution remains elusive. In this paper, we utilize SMOLM, single-molecule orientation localization microscopy, to directly measure the orientation spectra (3D orientation plus “wobble”) of lipophilic probes transiently bound to lipid membranes, revealing that Nile red's (NR) orientation spectra are extremely sensitive to membrane chemical composition. SMOLM images resolve nanodomains and enzyme-induced compositional heterogeneity within membranes, where NR within liquid-ordered vs. liquid-disordered domains shows a ≈4° difference in polar angle and a ≈0.3π sr difference in wobble angle. As a new type of imaging spectroscopy, SMOLM exposes the organizational and functional dynamics of lipid-lipid, lipid-protein, and lipid-dye interactions with single-molecule, nanoscale resolution. 相似文献
944.
945.
Toward Functional Type III [Fe]‐Hydrogenase Biomimics for H2 Activation: Insights from Computation
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Kevin A. Murray Dr. Matthew D. Wodrich Prof. Dr. Xile Hu Prof. Dr. Clémence Corminboeuf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3987-3996
The chemistry of [Fe]‐hydrogenase has attracted significant interest due to its ability to activate molecular hydrogen. The intriguing properties of this enzyme have prompted the synthesis of numerous small molecule mimics aimed at activating H2. Despite considerable effort, a majority of these compounds remain nonfunctional for hydrogenation reactions. By using a recently synthesized model as an entry point, seven biomimetic complexes have been examined through DFT computations to probe the influence of ligand environment on the ability of a mimic to bind and split H2. One mimic, featuring a bidentate diphosphine group incorporating an internal nitrogen base, was found to have particularly attractive energetics, prompting a study of the role played by the proton/hydride acceptor necessary to complete the catalytic cycle. Computations revealed an experimentally accessible energetic pathway involving a benzaldehyde proton/hydride acceptor and the most promising catalyst. 相似文献
946.
Tristan Butler Sasha E. Alden Madeleine Taylor Stephen Deese David A. Rider Matthew Laskoski 《Journal of polymer science. Part A, Polymer chemistry》2018,56(23):2630-2640
Blended resins were prepared from the resorcinol-based PEEK-like oligomeric phthalonitrile resin (RES) and tetrakis(phenylethynyl)benzene (TPEB), a high char yield arylacetylene resin. Initial probing of curing properties using differential scanning calorimetry, indicated that TPEB and RES co-cure when heated. Characterization of thermal properties using thermogravimetric analysis indicated that a 1:1 TPEB-RES blend (by weight) exhibited a char yield of 80% which was 6% larger compared to pure RES (74%). According to FTIR characterization, the enhanced thermal properties of TPEB-RES were the result of increased crosslinking density. Rheological studies of TPEB, RES, and TPEB-RES blends indicated that blended systems exhibit similar processing characteristics as RES resin. For example, resins display ideal viscosities and relatively large processing windows when cured at 175 °C. Alternatively, pure TPEB resin exhibits low viscosities when melted, which are not suitable for preparing composite materials. This study indicates that preparing TPEB-RES blends is an effect strategy for improving thermal performance of potential RES composites while still maintaining the required processability for fabrication of dense polymer composites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2630–2640 相似文献
947.
We leverage the results of the prequel [8], in combination with a theorem of D. Orlov to create a categorical covering picture for factorizations. As applications, we provide a conjectural geometric framework to further understand M. Kontsevich's Homological Mirror Symmetry conjecture and obtain new cases of a conjecture of Orlov concerning the Rouquier dimension of the bounded derived category of coherent sheaves on a smooth variety. 相似文献
948.
949.
Antimicrobial loading into and release from poly(ethylene glycol)/poly(acrylic acid) semi‐interpenetrating hydrogels
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Yong Wu Jing Liang Ferenc Horkay Matthew Libera 《Journal of Polymer Science.Polymer Physics》2016,54(1):64-72
Electrostatic interactions within a semi‐interpenetrating network (semi‐IPN) gel can control the postsynthesis loading, long‐term retention, and subsequent release of small‐molecule cationic antibiotics. Here, electrostatic charge is introduced into an otherwise neutral gel [poly(ethylene glycol) (PEG)] by physically entrapping high‐molecular‐weight poly(acrylic acid) (PAA). The network structure is characterized by small‐angle neutron scattering. PEG/PAA semi‐IPN gels absorb over 40 times more antibiotic than PAA‐free PEG gels. Subsequent soaking in physiological buffer (pH 7.4; 0.15 M NaCl) releases the loaded antibiotics for periods as long as 30 days. The loaded gels elute antibiotics with diffusivities of 4.46 × 10?8 cm2/s (amikacin) and 2.08 × 10?8 cm2/s (colistin), which are two orders of magnitude less than those in pure PEG gels where diffusion is controlled purely by gel tortuosity. The release and hindered diffusion can be understood based on the partial shielding of the charged groups within the loaded gel, and they have a significant effect on the antimicrobial properties of these gels. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 64–72 相似文献
950.