Preparation and characterization of amphiphilic poly(ethylene glycol) graft copolymers

Amphiphilic graft copolymers of alkyl methacrylates, methoxy poly(ethylene glycol) (PEG) acrylate, and acrylic acid were synthesized by free radical polymerization. PEG graft copolymers with respect to structure, composition, and average molecular weight were characterized by FT-IR,H-1 NMR, and GPC. The critical micelle concentration and molar mass of the polymeric micelles were determined by fluorescence spectroscopy using pyrene as the fluorescence probe and static laser light scattering, respectively. The formation of polymeric micelles was influenced by the balance of hydrophobicity and hydrophilicity and other factors such as molecular weight of the copolymer products. The molar mass of polymeric micelles increased with mole content of hydrophobic comonomers. Loading capacity and weight average partition coefficient for the pyrene molecules into polymeric micelles were estimated via fluorescence quenching by Cu2+. Fluorescence quenching studies of pyrene indicated that a loose structure of micelles was formed from the graft copolymer containing high content of hydrophilic monomethoxy poly(ethylene glycol) (mPEG) and acrylic acid.