Synthesis, characterization, rheological behavior, and shear response of hydrophobically modified polyacrylamide and network structure of its microhydrogel

Octylphenol polyoxyethylene acrylate (OP‐10‐AC) was synthesized, and then OP‐10‐AC was copolymerized with acrylamide (AM) to form hydrophobically modified polyacrylamide P(AM/OP‐10‐AC) through micellar copolymerization. OP‐10‐AC content and rheology behavior of P(AM/OP‐10‐AC) were investigated in detail. Especially, under the conditions of different test methods, P(AM/OP‐10‐AC) showed interesting shear responsive behavior. The results of rheology study show that OP‐10‐AC content, polymer solution concentration, salt solution concentration, and different test methods powerfully influenced shear viscosity of aqueous solutions of P(AM/OP‐10‐AC). In addition, according to the dynamic shear experimental results, the critical hydrogel concentration range (CHCR) could be confirmed for aqueous solutions of P(AM/OP‐10‐AC). Above CHCR, these polymer solutions were essentially a kind of microhydrogels, which could explain the effect of concentration and hydrophobe content on their shear viscosity and viscoelasticity from the microstructure's point of view.