Interaction between sodium oleate and partially hydrolyzed polyacrylamide: A rheological study

The interaction between sodium oleate (C17H33COONa) and partially hydrolyzed polyacrylamide (HPAM) was investigated by rheological measurements. Mainly four series with concentration of HPAM to be 0.1 wt%, 0.2 wt%, 0.4 wt% and 0.6 wt%, respectively, were studied. At low concentrations of C17H33COONa (cC17H33COONa<0.01 wt%)(cC17H33COONa<0.01 wt%), an increase in viscosity is observed due to interpolymer cross-linking through hydrogen bonding between C17H33COONa and HPAM. With increasing concentration of C17H33COONa, the repulsion between C17H33COONa micellar aggregates attached to the HPAM chains increases and the coil of HPAM shrinks. As a result, the network between C17H33COONa and HPAM collapses and the viscosity of the system decreases. Correspondingly, the critical angular frequency ω* obtained from oscillation measurements shows a decrease at low concentrations of C17H33COONa, passes through a minimum and then increases continuously at higher C17H33COONa concentrations. Polarized microscopic observations reveal a possible transition from three dimensional network structures to lamellar structures induced by C17H33COONa addition.