基于原子转移自由基聚合技术的偶氮苯星形液晶聚合物的合成与表征

Synthesis and Characterization of Tri-arm Star Side-chain Liquid Crystalline Polymers Containing Azobenzene via Atom Transfer Radical Polymerization

利用原子转移自由基聚合(ATRP)技术合成了含不同端基取代基的偶氮苯三臂星形侧链液晶聚合物.均苯三酚与2-溴异丁酰溴通过酯化反应制备三官能团引发剂,引发偶氮苯单体6-[4-(4-甲氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(MMAzo)或6-[4-(4-乙氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(EMAzo)的ATRP反应.利用核磁共振氢谱(1HNMR)、凝胶色谱(GPC)、差示扫描量热法(DSC)和偏光显微镜(POM)等手段对星形聚合物进行表征.星形聚合物的液晶性与相应均聚物相似,但偶氮苯端基取代基的不同导致星形聚合物的液晶性差别显著.在紫外/可见光照射下星形聚合物呈现明显的异构化转变.

Tri-arm star side-chain liquid crystalline（LC）polymers containing azobenzene with different terminal substituents were synthesized by atom transfer radical polymerization.Trifunctional initiator prepared by the esterification between phloroglucinol and 2-bromoisobutyryl bromide was utilized to initiate the polymerization of 6-[4-（4-methoxyphenylazo）phenoxy]hexyl methacrylate or 6-[4-（4-ethoxyphenylazo）phenoxy]hexyl methacrylate.The star polymers were characterized by ^1H NMR,gel permeation chromatography,differential scanning calorimetry,and polarizing optical microscopy.The tri-arm star side-chain LC polymer with p-methoxyazobenzene moieties exhibits a smectic and nematic phase,while that with p-ethoxyazobenzene moieties shows only a nematic phase,which derives from different terminal substituents.The star polymers have similar LC behavior to the corresponding linear homopolymers.Both star polymers show photoresponsive isomerization under the irradiation with UV-Vis light in THF solution.