(64g) Dynamics and Rheology of Polymer-Surfactant Association Complexes

The rheological properties of polymer-surfactant mixtures play a significant role in applications ranging from enhanced oil recovery, pharmaceutical and biological fluids, cosmetics, food, soft adhesives and coating. It is well stablished that addition of an ionic surfactant to an aqueous solution of neutral polymer like polyethylene oxide is known to result in a shear rheological response with non-monotonic concentration dependent variation, attributed to association complexes formed by hydrophobic interactions between surfactant monomers and polymers chains, as well as charge effects. Furthermore, the formation of association complexes changes both dynamic and equilibrium surface tension. However, due to a lack of suitable techniques, dynamic adsorption and extensional rheology response of polymer-surfactant mixtures have not been characterized in adequate detail remains relatively poorly understood even though drop formation or liquid transfer applications are influenced by adsorption kinetics, extensional rheology and pinching dynamics. In this study, we examine how pinch-off dynamics and extensional rheological response of polymer solutions (PEO) are modified by the addition of ionic surfactants (SDS), using the recently developed dripping-onto-substrate (DoS) rheometry protocols, and characterize dynamic adsorption using a home-built maximum bubble pressure tensiometry (MBPT). We find the PEO-SDS mixtures exhibit a weaker-concentration dependence variation in the extensional relaxation time, filament lifespan, and extensional viscosity response than anticipated by the shear rheology characterization. We finally discuss the implications of dynamic adsorption and extensional rheology response for dispensing of multicomponent complex fluids.