(539a) Molecular Design of Wormlike Surfactant Micelles – Effects of Branching

The molecular design of structured surfactants with optimal flow properties is critical to applications ranging from consumer products such as shampoos to enhanced oil recovery, where such complex fluids undergo both steady and dynamic nonlinear deformations during processing, transport, and use. To design such materials, a thorough understanding of the coupling between the molecular topology and the flow properties is required. Prof. Jack Zakin conducted foundational research in micellar solutions of cationic surfactants for rheology control applications. Building on his research in this work, novel spatio-temporial resolved flow-small angle neutron scattering (flow-SANS) and rheology measurements are performed on model systems of mixed ionic surfactants to understand this non-trivial coupling between the macroscopic flow behavior, molecular topology, and material performance. Such methods enable simultaneous measurements of the material microstructure during an applied shear deformation, which quantifies the structure-rheology relationship. Specifically, we study the role of branching in WLM solutions to alter or eliminate undesirable flow instabilities such as shear banding. This work provides a critical test of microstructure-based constitutive equations that incorporate micellar breakage and branching.