Synthesis, characterization and self-assembly of hybrid pH-sensitive block copolymer containing polyhedral oligomeric silsesquioxane (POSS)

In this study, a series of novel hybrid pH-sensitive block copolymers containing POSS (HBCPs), poly(methacrylisobutyl-POSS)-b-poly(4-vinylpyridine) (PMAiBuPOSS-b-P4VP) and poly(methacrylisobutyl-POSS)-b-polystyrene-b-poly(4-vinylpyridine) (PMAiBuPOSS-b-PS-b-P4VP), were synthesized via reversible addition fragmentation chain-transfer (RAFT) polymerization. Their structures and molecular weight were characterized via 1H NMR, GPC and TEM. Their self-assembly behaviors, including pH-sensitive behaviors and self-assembly morphologies in aqueous solution, were investigated via DLS and TEM. It was found that the size of aggregates in aqueous solution would initially decrease and later increase as the pH value increased. It is supposed that this behavior was caused by the pH sensitivity of the P4VP block of the HBCPs. Our hybrid triblock copolymers were found to assemble nanowires and nanospheres. Unique dot-like phase separation was also observed in the aggregates of the HBCPs at pH 1. Furthermore, we investigated the effects of block length and structure on the self-assembly morphologies of the HBCPs.