多嵌段共聚物(P4VP-b-PS-b-P4VP)_n的胶束化行为研究

MICELLIZATION BEHAVIOR OF MULTIBLOCK COPOLYMER (P4VP-b-PS-b-P4VP)_n

研究了一系列具有不同链段长度和组成的聚4-乙烯基吡啶-聚苯乙烯-聚4-乙烯基吡啶多嵌段共聚物(P4VP-b-PS-b-P4VP)n在其选择性溶剂甲苯和pH<3的水中的胶束化过程,主要研究了多嵌段共聚物链段长度、溶液浓度和溶剂对其胶束形态的影响.透射电镜和原子力显微镜结果表明随着P4VP段链的相对增长,多嵌段共聚物在甲苯中的胶束形态由蠕虫链状向短棒状到球状胶束变化,而其在pH<3的水溶液中均形成球形胶束.由于特殊的链结构,聚合物的浓度对(P4VP-b-PS-b-P4VP)n多嵌段共聚物的胶束行为和胶束形态有着重要的影响.同时,(P4VP-b-PS-b-P4VP)n多嵌段共聚物分子量分布的多分散性对其在选择性溶剂中的胶束形态也有所影响.

The micellization behavior of a series of muhiblock copolymers [ poly（4-vinylpyridine）-b-polystyrene-bpoly （4-vinylpyridine） ] n （P4VP-b-PS-b-P4VP） n in selective solvents, namely toluene and acidic water with pH 〈 3, was investigated by using transmission electron microscopy （TEM） and atomic force microscopy （AFM）. Three multiblock copolymers （P4VP-b-PS-b-P4VP）n were synthesized via reversible addition-fragmentation chain transfer （RAFT） polymerization with a cyclictri-thioearbonate as chain transfer agent. The muhiblock copolymers were relatively polydisperse with polydispersity indexes of ca. 1.74 - 2.19. The effects of block length, polymer concentration and selective solvent on the morphology of the muhiblock copolymer micelle were discussed. Because P4VP blocks have longer length than that of PS blocks and can not dissolved in toluene, the （P4VP-b-PS-b- P4VP） n multiblock copolymers showed rich micellar morphologies in toluene. The experimental results indicated thatthe morphology of muhiblock copolymer micelle in toluene changed from worm-like shape to short-rod and finally to spherical micelle as the length of P4VP block increased. The polymer concentration was found to have strong effects on the micelle morphology due to the special sequence structure of the multiblock copolymer. At low concentration, the multiblock copolymer tended to form spherical micelle in toluene. The polydispersity of molecular weight also affected the micelle morphology of the muhiblock copolymer. For acidic water with pH 〈 3, a selective solvent for the P4VP blocks, all of the multiblock copolymers studied here formed spherical micelles in it due to the longer block length of P4VP blocks.