Structural Changes during Polymerization of Acrylamide in Semidilute Solutions of Wormlike Surfactant Micelles

Abstract

The structure and rheological properties of aqueous solutions of the anionic surfactant potassium oleate and the water-soluble monomer acrylamide before and after radical polymerization have been studied. In the absence of monomer and in the presence of a low-molecular-weight salt, potassium oleate forms a network of long entangled cylindrical (wormlike) micelles. The addition of the monomer does not lead to a change in their cylindrical shape and radius, but it promotes the transformation of branched micelles into linear ones. The structure of surfactant aggregates changes significantly after polymerization: according to neutron scattering data, it becomes bicontinuous and its local geometry becomes lamellar. The coexistence of such a structure with polyacrylamide macromolecules in a semidilute solution leads to a significant synergistic increase in viscosity and elastic modulus.