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

Abstract

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 (Mn = 9200 and Mw/Mn = 1.62) groups is prepared first by condensation of α, ω-dihydroxyl poly(ethylene oxide) with S, S″Bis(α, α′-dimethyl- α′-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), 1H 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. © 2006 Wiley Periodicals, Inc.