Dispersion copolymerization of polyoxyethylene macronomer and styrene 4. Solution properties of polystyrene-graft-polyoxyethylene copolymers

The graft copolymers (polystyrene-graft-polyoxyethylene) (PSt-graft-PEO) we re prepared by the radical dispersion copolymerization of methacryloyl (MA) -terminated PEO macromonomer and styrene. By means of size-exclusion chroma tography, liquid chromatography at the critical adsorption point, and light scattering, the molecular weight parameters and the solution properties of PSt-graft-PEO were investigated. The apparent average molecular weight and the molecular weight distribution (MWD) of graft copolymers were found to decrease with increasing molecular weight of PEO-MA macromonomer. This decr eased molecular weight was attributed to the chain transfer to PEO unit and increased contribution of the solution polymerization. The broad MWD varie d with the ratio of the polymerization in the continuous phase and the poly mer particles. The number of PEO grafts per PSt backbone decreased with inc reasing molecular weight of the PSt-graft-PEO copolymer, which was attribut ed to the intramolecular association of PEO segments. The intrinsic viscosi ty or the coil size of graft copolymer molecules varied with temperature as a result of the dehydration of PEO segments. (C) 1999 John Wiley & Sons, I nc.