The interactions between novel hydrophobically associating copolymer P(AM/POEA) and surfactants (SDS and CTAB) were studied in aqueous solution using viscometry, fluorescence probe and transmission electronic microscopy (TEM). The structure of the P(AM/POEA) consists of randomly distributed blocks of hydrophobe, 2-phenoxyethyl acrylate (POEA) in the polyacrylamide backbone. The polymer of this type easily interacts with surfactants SDS and CTAB through hydrophobic association to form a mixed micelle-like aggregate, resulting in a large viscosity enhancement. With the addition of SDS to the polymer solution, the viscosity varied dramatically and a pronounced maximum appeared at surfactant concentration around its CMC, which was found to be independent of the microstructure of polymer. However, their degree of associative thickening behavior was closely related to the hydrophobe content X_H and block size N_H of polymer. The larger the X_H or N_H, the higher the viscosity within the experimental concentration range. The morphology of the network structure for polymer/surfactant aggregates was also directly observed by TEM.

Key words: copolymer P(AM/POEA), polymer/surfactant system, microstructure, viscosity, hydrophobic association