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Kalman Toth Nur Cicek Kekec Nihan Nugay Joseph. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2016,54(8):1119-1131
We describe the synthesis, characterization, and select properties of a novel polyurethane (PU) prepared using a new polyisobutylene diol, HO‐CH2CH2‐S‐PIB‐S‐CH2CH2‐OH, soft segment and conventional hard segments. The diol is synthesized by terminal functionalization of ally‐telechelic PIB followed by low‐cost thiol‐ene click chemistry. Properties of ‐S‐ containing PU (PIBS‐PU) containing 72.5% PIB were investigated and compared to similar PUs made with HO‐PIB‐OH (PIBO‐PU). Hydrolytic resistance was studied by contact with phosphate‐buffered saline, oxidative resistance by immersing in concentrated HNO3, and metal ion oxidation resistance by exposure to CoCl2/H2O2. Hydrolytic and oxidative resistances of PIBS‐PU and PIBO‐PU are similar and superior to a commercial PDMS‐based PU, Elast‐Eon? E2A. According to 1H NMR spectroscopy the ‐S‐ in PIBS‐PUs remained unchanged upon treatment with HNO3, however, oxidized mainly to ‐SO2‐ by CoCl2/H2O2. Static mechanical properties of PIBS‐PU and PIBO‐PU are similar, except creep resistance of PIBS‐PU is surprisingly superior. The thermal stability of PIBS‐PUs is ~15 °C higher than that of PIBO‐PU. FTIR spectroscopy indicates H bonded S atoms (N‐H…S) between soft and hard segments, which noticeably affect properties. DSC and XRD studies suggest random low‐periodicity crystals dispersed within a soft matrix. Energy dispersive X‐ray spectroscopy–scanning electron microscopy indicates homogeneous distribution of S atoms on PIBS‐PU surfaces. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1119–1131 相似文献
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Automatized Parameterization of the Density‐functional Tight‐binding Method. II. Two‐center Integrals
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Henryk A. Witek Chien‐Pin Chou Grzegorz Mazur Yoshifumi Nishimura Stephan Irle Bálint Aradi Thomas Frauenheim Keiji Morokuma 《中国化学会会志》2016,63(1):57-68
We present an efficient numerical integration scheme (TWOCENT) to be used in the context of automatized parameterization of the density‐functional tight‐binding (DFTB) method. The accuracy of the integration process is assessed and its range of applicability is discussed. The functionality of the developed code is tested by reproducing the electronic portion of the existing mio parameter sets and by reproducing a series of reference DFT band structures of elemental solids. 相似文献
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Martin B. Hocking Keith A. Klimchuk Stephen Lowen 《Journal of polymer science. Part A, Polymer chemistry》2001,39(12):1960-1977
The preparation of a series of copolymers of N‐t‐butylacrylamide (NTBAM) with acrylamide (AM) is reported. The insolubility of NTBAM in water led to the testing of methanol, t‐butanol, and mixtures of these solvents with water to obtain effective copolymerization. Several of these polymerizations produced nonhomogeneous product mixtures. Samples of the components were separated and characterized by photoacoustic Fourier transform infrared spectroscopy and 13C NMR spectroscopy. Hydrodynamic volumes of the products were obtained from solution‐viscosity measurements, gel permeation chromatography, and multi‐angle laser light scattering methods. The NTBAM‐co‐AM copolymers had degrees of polymerization and molecular weights in the 4.1–5.9 × 104 monomer units and 3.25–4.5 × 106 g/mol range, respectively. They contained from 15 to 36 mol % NTBAM. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1960–1977, 2001 相似文献
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