Water-soluble copolymers. 37. Synthesis and characterization of responsive hydrophobically modified polyelectrolytes

Abstract

Hydrophobically-modified, water-soluble polyelectrolytes have been prepared by a micellar technique from acrylamide, n-decylacrylamide, and a third monomer, sodium 3-acrylamido-3-methylbutanoate, sodium acrylate, or sodium 2-acrylamido-2-methylpropanesulfonate. These terpolymers exhibit rheological behavior dependent upon the terpolymer composition, nature of the charged monomer, ionic strength, and pH. Although the hydrophobic monomer is incorporated in low concentration, the associative effects are profound, with some compositions maintaining high viscosity in NaCl concentrations of up to 0.514 M. Hydrophobic associations in terpolymers with the carboxylate anion are stronger than those in structurally analogous terpolymers containing the sulfonate anion, especially at high NaCl concentrations. Within the carboxylate series, copolymers with the carboxylate group closer to the polymer backbone exhibit greater viscosity increases with added electrolyte above the critical overlap concentration, C*. Presence of carboxylate or sulfonate groups farther from the macromolecular backbone disrupts to a greater extent such hydrophobic associations.