SYNTHESIS AND SELF-ASSEMBLY OF AMPHIPHILIC TRI-BLOCK COPOLYMERS CONTAINING GLYCOPOLYMER SEGMENTS

Abstract

A series of tri-block copolymers of methyl methacrylate (MMA) and 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose ( MAIPGal ) were synthesized by sequential atom transfer radical polymerization (ATRP) of MMA and MAIPGal,using 4,4'-biphenol di(2-bromoisobutyrate) (BiBBP) as the initiator. The chemical composition and molecular weights of the copolymers were characterized by 1H-NMR and GPC. It was demonstrated that the block chain length of both PMMA and PMAIPGal can be tuned by the feed molar ratio and monomer conversion. After de-protecting the isopropylidene groups of PMAIPGal,amphiphilic tri-block copolymers were obtained. Their self-assembly behavior in water was investigated by TEM. We investigated the effects of polymer structure,composition and initial concentration in good solvents on the final morphologies of the aggregates. For BAB copolymers,with the hydrophobic PMMA in the center,when the hydrophilic PGA was short,they tended to form vesicle like assemblies at lower polymer concentration. Increasing the chain length of the PGA chain,large irregular micelles were obtained. For ABA copolymers,small sized micelles were the main morphologies,but they were connected with each other due to the interaction of the PGA segments. The difference of self-assembly behavior was attributed to the polymer structure,which dominates the molecular packing as well as the chain segregation of the glycopolymer chains.