The Aggregation Behavior of Poly(ethylene oxide)-Poly(methyl methacrylate) Diblock Copolymers in Organic Solvents

Abstract

Poly(ethylene oxide)-poly(methyl methacrylate) and poly(ethylene oxide)-poly(deuteromethyl methacrylate) block copolymers have been prepared by group transfer polymerization of methyl methacrylate (MMA) and deuteromethyl methacrylate (MMA-d 8 ), respectively, using macroinitiators containing poly(ethylene oxide) (PEO). Static and dynamic light scattering and surface tension measurements were used to study the aggregation behavior of PEO-PMMA diblock copolymers in the solvents tetrahydrofuran (THF), acetone, chloroform, N.N-dimethylformamide (DMF), 1,4-dioxane and 2,2,2-trifluoroethanol. The polymer chains are monomolecularly dissolved in 1,4-dioxane, but in the other solvents, they form large aggregates. Solutions of partially deuterated and undeuterated PEO-PMMA block copolymers in THF have been studied by small-angle neutron scattering (SANS). Generally, large structures were found, which cannot be considered as micelles, but rather fluctuating structures. However, 1 H NMR measurements have shown that the block copolymers form polymolecular micelles in THF solution, but only when large amounts of water are present. The micelles consist of a PMMA core and a PEO shell.