Highly Branched Waxy Potato Starch-Based Polyelectrolyte: Controlled Synthesis and the Influence of Chain Composition on Solution Rheology

In the present work, a series of highly branched random copolymers of acrylamide (AM), sodium 2-acrylamido-2-methyl-1-propanesulfonate (SAMPS), and N-isopropylacrylamide (NIPAM) were prepared by using water-soluble waxy potato starch-based macroinitiator via aqueous Cu0-mediated living radical polymerization (25 °C). The AM/SAMPS/NIPAM ratio was varied to investigate the influence of chain composition on the aqueous rheological properties of the prepared copolymers. Rheological results indicated an optimum SAMPS intake (25 mol %) for the balanced performance of viscosity and salt resistance in saline water. The intake of NIPAM units (e.g., 25 mol %), contrary to what was expected, undermines the thickening ability of the copolymers in saline water because of hydrophobic association. In high salinity solution, thermo-thickening behavior can be observed at low shear rates (γ≤ 3 s-1) because of the screening effect of salt on the negatively charged SAMPS units. At the high shear rate, the thermo-thickening behavior disappears because of the disruption of the NIPAM aggregates. These results pave the way toward the use of the prepared polymers as rheology modifiers in a variety of possible formulations for different applications, in particular in enhanced oil recovery.