一种含乙氧羰基偶氮苯液晶三嵌段共聚物的合成与表征

SYNTHESIS AND CHARACTERIZATION OF A LIQUID CRYSTALLINE TRIBLOCK COPOLYMER CONTAINING ETHOXYCARBONYLAZOBENZENE UNITS

利用原子转移自由基聚合(ATRP),合成了一种含有乙氧羰基偶氮苯的液晶三嵌段共聚物,并合成了一种同样偶氮生色团的均聚物进行对比.均聚物(PC6ET)由偶氮单体甲基丙烯酸{6-[4-(4-乙氧羰基苯基偶氮)苯氧基]己酯}(C6ET)的ATRP反应制备.嵌段共聚物的合成,先通过聚环氧乙烷(PEO)和过量的2-溴异丁酰溴、三乙胺反应,得到双端大分子引发剂(Br-PEO-Br);再进一步通过C6ET的ATRP反应,得到了三嵌段共聚物(PC6ET-PEO-PC6ET).热分析、偏光显微镜观察和X射线衍射实验证实,合成的均聚物和嵌段共聚物均为近晶型液晶聚合物.三嵌段共聚物的液晶清亮点比均聚物的稍低.

The synthesis and characterization of a liquid-crystalline triblock copolymer containing ethoxycarbonylazobenzene units were described.The methacrylate containing ethoxycarbonylazobenzene functional group,6-（4-（4-ethoxycarbonylphenylazo）phenoxy）hexyl mathacrylate（C6ET）,was prepared as the monomer.For the synthesis of the triblock copolymer,a macro-initiator was prepared by the reaction of PEO-2000 with an excessive amount of 2-bromoisobutyryl bromide catalyzed with triethylamine.The ABA triblock copolymer（PC6ET-PEO-PC6ET） was obtained by ATRP of C6ET with the macroinitiator.For comparison,a homopolymer PC6ET also was obtained by the atom transfer radical polymerization（ATRP） of C6ET.UV-Vis spectroscopy,FT-IR spectroscopy,1H-NMR analysis and GPC measurements were used to characterize the structure and molecular weights of the products.Thermal analysis,optical microscopy and X-ray diffraction were used to characterize the LC phase types and phase-transition temperature.Results show that PC6ET is a liquid crystalline polymer with smectic phase.The clearing temperature of the homopolymer was 20℃ higher than the corresponding azo polymer with alkoxyl groups,which indicated the effect of substitutents on the liquid crystalline properties.The cleaning temperature of the ABA triblock copolymer PC6ET-PEO-PC6ET was slightly lower than that of the homopolymer.The phase transition temperatures of the homopolymer and block copolymer were determined to be Cr 70 s 153 i 151 s 58 g,and Cr 65 s 139 i 139 s 48 g（℃） respectively.The azobenzene-containing block copolymer could be used as a potential photo-induced self-assemble system.