H. Derand et al., POLY(ETHYLENE GLYCOL) GRAFT-COPOLYMERS CONTAINING CARBOXYLIC-ACID GROUPS - AGGREGATION AND VISCOMETRIC PROPERTIES IN AQUEOUS-SOLUTION, Macromolecules, 29(27), 1996, pp. 8770-8775
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.