POLY(ETHYLENE GLYCOL) GRAFT-COPOLYMERS CONTAINING CARBOXYLIC-ACID GROUPS - AGGREGATION AND VISCOMETRIC PROPERTIES IN AQUEOUS-SOLUTION

Poly(ethylene glycol) monomethyl ethers (MPEG) were grafted on copolym ers of maleic anhydride and styrene, methyl methacrylate, and ethylhex yl methacrylate, respectively. Hydrolysis of the remaining anhydride r esidues gave graft copolymers carrying a large number of carboxylic ac id groups along the main chains. The properties in aqueous solutions o f these graft copolymers were studied with respect to aggregation beha vior and viscometric properties, Aggregation of the polymers was exami ned by quasi-elastic light scattering and now field-flow fractionation in water and KCl solution. Both methods showed that the anionic graft copolymers mainly were present as single molecules in pure water, wit h a minor fraction of aggregates. In KCI solution, aggregates with ave rage sizes of approximately 30 nm were the dominant species. In aqueou s solution, the polymers exhibited polyelectrolyte behavior, i.e., a d ramatic increase of the viscosity upon neutralization. Graft copolymer s with hydrophobic groups in the backbone had lower viscosities.