Effect of the structure of amphiphilic poly(ethylene glycol)-containing graft copolymers on styrene emulsion polymerization

Amphiphilic graft copolymers consisting of monomeric units of poly(ethylene glycol) monomethyl ether acrylate, lauryl or stearyl methacrylate, and 2-hydroxyethyl methacrylate were synthesized and characterized. The effectiveness of these poly(ethylene glycol)-containing graft copolymers in stabilizing styrene emulsion polymerization was evaluated. The polymerization rate (RP) increases with increasing graft copolymer concentration, initiator concentration, or temperature. At a constant graft copolymer concentration, RP increases, and the amount of coagulum decreases with the increasing hydrophilicity of graft copolymers. The polymerization system does not follow Smith-Ewart case II kinetics. The desorption of free radicals out of latex particles plays an important role in the polymerization kinetics. The overall activation energy and the activation energy for the radical desorption process are 85.4 and 34.3 kJ/mol, respectively. (C) 2002 Wiley Periodicals, Inc.