三臂对称星形偶氮苯聚合物的合成与表征

通过均苯三酚与2-溴异丁酰溴的酯化反应,得到三官能团引发剂;以苯甲醚为溶剂,在CuB r/1,1,5,5,7-五甲基二亚乙基三胺催化体系下,三官能团引发剂引发偶氮苯单体6-[4-(4-乙氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯进行原子转移自由基聚合反应合成三臂对称星形偶氮苯聚合物。通过凝胶渗透色谱与核磁共振氢谱对三臂对称星形偶氮苯聚合物进行结构表征;利用示差扫描量热法与偏光显微镜分析了其热行为和液晶性。实验结果表明,三臂对称星形偶氮苯聚合物和对应的偶氮苯线型均聚物的液晶性相似,均显示向列相,且在室温下相态能稳定保持。与偶氮苯线型均聚物相比,三臂对称星形偶氮苯聚合物的玻璃化转变温度有所提高,而液晶相转变点的焓变降低。

Synthesis and Characterization of 3-Arm Symmetric Star-Shaped Azobenzene Polymer

3-Arm symmetric star-shaped azobenzene polymer was synthesized by atom transfer radical polymerizatiom(ATRP).The polymerization of 6-[4-(4-ethoxyphenylazo)phenoxy]hexylmethycrylate was carried out at 85℃ for 20h by using trifunctional group initiator,which was prepared by the esterification of phloroglucinol with 2-bromoisobutylryl bromide,CuBr/1,1,5,5,7-pentamethyldiethylenetriamine as catalytic system and anisole as solvent.The star-shaped polymer was characterized by means of gel permeation chromatography and ~1H NMR.The thermal and liquid crystalline properties of the polymer were investigated by means of DSC and polarized optical microscopy(POM).It was found that starshaped polymer has similar liquid crystalline behavior to corresponding azobenzene linear homopolymer.They all show nematic phase and are stable even at room temperature.Glass transition temperature(68℃)of star polymer is higher than that of homopolymer(62℃),but enthalpy of mesophase transition is lower.