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Yaming Niu Xiaoliang Zhu Lingzhi Liu Yan Zhao Zhenhua Jiang 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1459-1467
The new monomer (4‐(4′‐trifluoromethyl)phenoxyphenyl)hydroquinone (TFPOPH) was synthesized in a three‐step synthesis. A series of poly(aryl ether ketone) copolymers were prepared by the reaction of (4‐(4′‐Trifluoromethyl)phenoxyphenyl)hydroquinone and hydroquinone (HQ) with 4,4′‐difluorobenzophenone (DFB) in the presence of potassium carbonate in tretramethylene sulfone (TMS). Thermal analyses of the fluorinated copolymers showed that the glass transition temperature and 5.0% weight loss temperature are similar with that of PEEK, and the crystallinity decreased with increasing of TFPOPH. For the copolymer synthesized with the molar fraction of TFPOPH in the diphenol monomers (TFPOPH, HQ) being over 0.2, no cold crystallization temperature and melting temperature were detected, indicating that these copolymers are almost amorphous. The crystal structure of the copolymers with the molar fraction of TFPOPH being not higher than 0.2 is rhombic. The solubility in polar aprotic solvents of poly(aryl ether ketone)s copolymers increases and dielectric constant decreases step by step. 相似文献
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Langang Niu Ramaswamy Nagarajan Dingsong Feng Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1983-1990
Main‐chain thermotropic liquid‐crystalline polyesters containing rigid biphenyl mesogens and flexible spacers were synthesized by chemo‐enzymatic route. The enzyme‐catalyzed polymerization showed high regio‐ and chemo‐ selectivity, and is environmentally friendly. The resulting polyesters were characterized with 1H‐NMR, 13C‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and polarized light optical microscopy (POM). 相似文献
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Highlights? The complete gougerotin biosynthetic gene cluster is cloned ? Heterologous production of gougerotin is accomplished in S. coelicolor M1146 ? Biosynthetic pathway is proposed based on bioinformatics, genetic, and chemical analyses ? Preliminary data support an uncommon enzymatic reaction for peptide bond formation 相似文献
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Seeking visible‐light‐active photocatalysts for efficient solar‐energy conversion has become an intensifying endeavor worldwide. In this concept paper, general requirements for finding new visible‐light‐active photocatalysts are briefly introduced, and recent progress in exploring elemental photocatalysts for clean‐energy generation and environmental remediation are reviewed. Finally, opportunities and challenges facing elemental photocatalysts are discussed. 相似文献