Modulation of rheological behaviors of hydrophobically modified polyacrylamide based on micellar kinetics

Rheological behaviors of the aqueous solution of N-benzylacrylamide-modified partially hydrolyzed polyacrylamide in the presence of various surfactants are compared in this study. In addition to the electrostatic contribution, the steric factor of the surfactant molecules is found to play an important role in tuning the rheology of polymer solution presumably through diverse kinetics of mixed micelles composed of both surfactants and polymers. Specifically, it is speculated that faster micellar kinetics typical of smaller surfactant molecules allows the restructuring of micelles from intrapolymeric liaisons to interpolymeric ones when shear rate increases, giving rise to the unusual Newtonian and dilatant characteristics, while the impact of larger surfactant molecules is largely independent of the shear rate due to slower micellar kinetics. The possibility of the same polymer manifesting diverse rheological behaviors through fine-tuning added surfactants and associated micellar kinetics can be of great interests in applications such as enhanced oil recovery and painting formulation.