Micelle formation and sol-gel transition behavior of comb-like amphiphilic poly((PLGA-b-PEG)MA) copolymers

Comb-like amphiphilic poly(poly((Iactic acid-co-glycolic acid)-block-poly (ethylene glycol)) methacrylate (poly((PLGA-b-PEG)MA)) copolymers were synthesized by radical polymerization. (PLGA-b-PEG)MA macromonomer was prepared by ring-opening bulk polymerization Of DL-lactide and glycolide using purified poly(ethylene glycol) monomethacrylate (PEGMA) as an initiator. (PLGA-b-PEG)MA macromonomer was copolymerized with PEGMA and/or acrylic acid (AA) by radical polymerization to produce comb-like amphiphilic block copolymers. The molecular weight and chemical structure were investigated by GPC and H-1 NMR. Poly((PLGA-b-PEG)MA) copolymer aqueous solutions showed gel-sol transition behavior with increasing temperature, and gel-to-sol transition temperature decreased as the compositions of the hydrophilic PEGMA and AA increased. The gel-to-sol transition temperature of the terpolymers of the poly((PLGA-b-PEG)AM-co-PEGMA-co-AA) also decreased when the pH was increased. The effective micelle diameter obtained from dynamic light scattering increased with increasing temperature and with increasing pH. The critical micelle concentration increased as the composition of the hydrophilic monomer component, PEGMA and AA, were increased. The spherical shape of the hyper-branched polymers in aqueous environment was observed by atomic force microscopy. (C) 2008 Wiley Periodicals, Inc.