阳离子两亲性三嵌段共聚物的合成及自组装

Synthesis and Self-Assembly of Cationic Amphiphilic Triblock Copolymers

采用可逆加成-断裂链转移(RAFT)自由基聚合及季铵化后处理方法制备出2种苯乙烯(St)和对氯甲基苯乙烯(VBC)的阳离子两亲性三嵌段共聚物PS-b-Q-PVBC-b-PS和Q-PVBC-b-PS-b-Q-PVBC。PS和PS-b-PVBC-b-PS的相对分子质量分别为8100和11700;PVBC和Q-PVBC-b-PS-b-Q-PVBC的相对分子质量分别为3600和12700,可以发现,二者的相对分子质量和嵌段比例均相近。以二甲基甲酰胺(DMF)为共溶剂,分别以去离子水和甲苯为选择性溶剂,对2种聚合物的自组装行为进行对比研究,探索了分子结构对聚合物自组装行为的影响。结果表明,当在相同的条件下进行自组装时,若成壳嵌段在大分子两端,聚合物自组装产生球形胶束聚集体;若成壳嵌段在大分子中间,聚合物自组装形态则是核壳胶束聚集体(选择性溶剂含量较低时)或棒状、球状胶束的聚集体(选择性溶剂含量较高时)。

Reversible addition fragmentation chain transfer(RAFT)was applied to prepare triblock copolymers polystyrene-b-poly(vinylbenzyl chloride)-b-polystyrene(PS-b-PVBC-b-PS)and poly(vinylbenzyl chloride)-b-polystyrene-b-poly(vinylbenzyl chloride)(PVBC-b-PS-b-PVBC).Cationic amphiphilic triblock copolymers PS-b-Q-PVBC-b-PS and Q-PVBC-b-PS-b-Q-PVBC were prepared by quaternarization of 1-chloromethyl-4-ethenylbenzene(VBC)with excess triethylamine.The molecular weight and molecular weight distributions of macro-CTA and corresponding triblock copolymers were obtained by GPC.The structure of polymers was characterized by FT-IR and 1 H-NMR spectra.The results show that珨Mnof PS,PS-b-PVBC-b-PS,PVBC and PVBC-b-PS-b-PVBC is 8100,11700,3600 and 12700respectively.珨Mnand the block ratio of the two cationic amphiphilic triblock copolymers are nearly the same.The effect of polymers chain architecture on self-assemble aggregate morphologies of copolymers in different selective solvents was observed by TEM.It's found that,under same conditions,aggregate morphologies are spheres in amphiphilic triblock copolymers with the coronaforming segment at the end;and for the amphiphilic triblock copolymers with the corona-forming segment in the middle,the aggregate morphologies are core-corona micelles(with relatively low content of selective solvent)or rods mixed with irregular spheres(with higher content of selective solvent).