可逆加成-断裂链转移方法合成两亲液晶嵌段功能大分子及其自组装的研究

采用可逆加成-断裂链转移(RAFT)可控聚合反应方法,合成制备了一系列窄分子量分布、结构规整的两亲液晶嵌段功能大分子聚甲基丙烯酸亚己基胆固醇酯-b-聚甲基丙烯酸羟乙酯(PMA6Chol-block-PHEMA).运用核磁共振(NMR)、凝胶渗透色谱仪(GPC)、示差扫描热分析仪(DSC)和热失重分析仪(TGA)对制备所得两亲嵌段功能大分子的化学结构、热物理性能以及液晶相结构与转变温度进行了研究.在此基础上,采用纳米沉淀法研究了所得系列液晶嵌段功能大分子在混合溶剂中的自组装,制备得到微米尺度球形组装体.研究结果表明刚性胆固醇液晶共聚单元的存在对于溶液自组装产生重要影响.

PREPARATION OF NEW CHOLESTEROL-BASED AMPHIPHILIC LIQUID-CRYSTALLINE DIBLOCK COPOLYMERS via RAFT APPROACH AND THEIR THERMAL PROPERTIES AND SELF-ASSEMBLY IN MIXED SOLUTIONS

A new series of amphiphilic diblock liquid crystalline copolymers denoted as PMA6Chol-block-PHEMA were prepared by sequential reversible addition-fragmentation chain transfer polymerization(RAFT) and successive removal of TMS protection groups,and their chemical structures were further characterized by 1H-NMR and GPC.By means of differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA),thermal properties and liquid crystal phase transitions were characterized for the resultant diblock copolymers,and the presence of hydrophilic PHEMA hydrogen-bond network may be one possible reason of higher TLC-I of diblock copolymers than those of PMA6Chol homopolymers.Through nanoprecipitation in THF/water mixed solutions,the synthesized LC diblock copolymers PMA6Chol-block-PHEMA were found to self-assemble into micron-scale core-shell spherical aggregates,and the rapid kinetically trapping rigid LC PMA6Chol chains may be the reason for self-assembling microscopic spheres at ambient temperatures in THF/water mixed solutions.