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Jing-wu Wang Shi-jun Zheng Xiao-hui Xu Xing-qi Zhu Shu-yuan Zhang Tie-sheng Li Zi-fa Li Qi-feng Zhou 《高分子科学》2005,(5):549-556
A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy) dibenzoyl dichloride (M1), 2,5-bis(p-octyloxybenzoyloxy) hydro-quinone (M2) and cis-4,4′-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 (M3). Monomer M1 was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid, monomer M2 was synthesized by esterfication and reduction reaction of 2,5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high,and the intrinsic viscosity [η] of copolyesters ranges from 0.25-0.35. The monomers' structures were identified by using elemental analysis, IR, UV, 1H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHCl3 at room temperature except CP9. The properties of copolyesters were investigated by using GPC, [η] , DSC, TG,WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature (Tm). The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 unit in the copolyesters. 相似文献
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Polystyrene-block-poly(5,6-benzo-2-methylene-1,3-dioxepane) (PSt-b-PBMDO), poly(methyl methacrylate)-block-PBMDO (PMMA-b-PBMDO) and poly(methyl acrylate)-block-PBMDO (PMA-b-PBMDO) were synthesized by two-step atom transfer radical polymerization (ATRP) of conventional vinyl monomers, then BMDO. First, the polymerization of St, or MMA, or MA was realized by ATRP with ethyl α-bromobutyrate (EBrB) as initiator in conjunction with CuBr and 2,2′-bipyridine (bpy). After isolation, polymers with terminal bromine, PSt-Br, PMMA-Br and PMA-Br, were obtained. Second, the ATRP of BMDO was performed by using macroinitiator, PSt-Br (or PMMA-Br, PMA-Br) in the presence of CuBr/bpy. The structures of block copolymers were characterized by 1H NMR spectra. Molecular weight and polydispersity index were determined on gel permeation chromatograph. Among the block copolymers obtained, PMA-b-PBMDO shows the most narrow molecular weight distribution. 相似文献
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Thermoplastic elastomers show considerable flow if they are subjected to large strains. To investigate the influence of stress induced crystallization, elastomers showing stress induced crystallization are synthesized by hydrogenation of poly(butadienes) and poly(styrene-b-butadiene-b-styrene) block polymers. The influence of the methylene sequence length on the crystallization behaviour is evaluated. From stress relaxation experiments, the crystallization kinetic is analyzed. Heterogeneous nucleation and fibrillar crystal growth is detected for all block polymer systems. The kinetic behaviour is described by a preorientation of elastomer chains near the domain surface.Dedicated to Prof. Dr. R. Kosfeld on the occasion of his 60th birthday. 相似文献