Synthesis and self-assembly morphologies of amphiphilic multiblock copolymers [poly(ethylene oxide)b-polystyrene]n via trithiocarbonate-embedded PEO macro-RAFT agent

An amphiphilic multiblock copolymer [poly(ethylene oxide)-b-polystyrene](n) [(PEO-b-PS)(n)] is synthesized by using trithiocarbonate-embedded PEO as macro-RAFT agent. PEO with four inserted trithiocarbonate (M-n = 9200 and M-w/M-n, = 1.62) groups is prepared first by condensation of alpha, omega-dihydroxyl poly(ethylene oxide) with S, S ' Bis(alpha, alpha '-dimethyl-alpha ''-acetic acid)-trithiocarbonate (BDATC) in the presence of pyridine, then a series of goal copolymers with different St units (varied from 25 to 218 per segment) are obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization. The synthesis process is monitored by size exclusion chromatography (SEC), H-1 NMR and FT-IR. The self-assembled morphologies of the copolymers are strongly dependent of the length of PS block chains when the chain length of PEO is fixed, some new morphologies as large leaf-like aggregates (LLAs), large octopus-like aggregates (LOAs), and coarse-grain like micelles (CGMs) are observed besides some familiar aggregates as large compound vesicles (LCVs), lamellae and rods, and the effect of water content on the morphologies is also discussed. (c) 2006 Wiley Periodicals, Inc.