探究环状拓扑结构在聚合诱导自组装中的影响

Exploring the topological effect of linear and cyclic macroCTAs during polymerization-induced self-assembly(PISA)

近些年,聚合诱导自组装得到了广泛的关注,但使用环状聚合物作为聚合诱导自组装的大分子链转移剂的研究还尚未报道。为此,本文合成了环状和线形两种聚乙二醇大分子链转移剂,分别以甲基丙烯酸苄酯和2,3,4,5,6-五氟苯乙烯为单体进行可逆加成断裂链转移分散聚合,研究了拓扑结构对聚合动力学和嵌段聚合物组装体形貌转变的影响。研究发现,环状拓扑结构可以延长聚合诱导自组装过程的成核期,同时嵌段聚合物组装体的形貌转变也会被延迟,这可能是由于环状聚乙二醇具有更好的溶解性。

Polymerization-induced self-assembly(PISA) is a robust strategy for the syntheses of block copolymer nanoobjects with various morphologies.Although PISA has been extensively studied,the use of cyclic macromolecular chain transfer agents(macro CTAs) as the hydrophilic block has not been reported.We explored the effects of macro CTA topology on the polymerization kinetics and morphologies of block copolymer assemblies during reversible addition-fragmentation chain transfer(RAFT) dispersion polymerization.To this end,linear and cyclic poly(ethylene oxide)(PEO) with 4-(4-cyanopentanoic acid) dithiobenzoate(CPADB) groups were synthesized and used as CTAs to mediate the RAFT polymerization of benzyl methacrylate(Bz MA) and 2,3,4,5,6-pentafluorostyrene(PFSt) under PISA formulation.Interestingly,the nucleation period of the linear PEO is slightly shorter than that of its cyclic analog,and the cyclic hydrophilic segment leads to a delayed morphological transition during PISA.