RHEOLOGICAL PROPERTIES OF HYDROPHOBICALLY MODIFIED ACRYLAMIDE-BASED POLYELECTROLYTES

Associative polymers of acrylamide and n-decylacrylamide with sodium-3-acrylamido-3-methylbutanoate, sodium acrylate, or sodium-2-acrylamido-2-methylpropanesulfonate have been prepared by a micellar technique. Low shear rheometry was used to obtain plots of apparent viscosity as functions of ionic group type and mole percent incorporation into the backbone, polymer concentration and solution ionic strength. Results indicate that these polymers maintain high viscosity in NaCl concentrations of up to 0.514 M by intermolecular association of the hydrophobic groups. The amount of aggregation is dependent on the type of ionic group incorporated as well as the distance of the charged group from the backbone. Maximum increases in apparent viscosity are observed for the terpolymers containing carboxylate groups close to the polymer backbone. A conceptual model based on placement of both charged and hydrophobic groups along the macromolecular backbone is proposed consistent with rheological behavior.