(163ba) Shear-Induced Structure & Rheology of a Polymeric Sponge Phase

Sponge phases are typically found over certain composition ranges in water/surfactant mixtures, and are characterized by two interpenetrating domains of water separated by a convoluted surfactant bilayer membrane. More recently it has been that similar sponge phases may be found in blends of hompolymer (A) and triblock copolymers (A-B-A) [Falus et al., Phys. Rev. Lett. 93:145701, 2004]. Such polymer sponge phases should be useful models for studying dynamics and flow-induced structure, since the higher viscosity of the polymer matrix slows dynamics to a more readily accessible time scale. Following the work of Falus et al., we have constructed a sponge phase sample from polystyrene homopolymer and a triblock copolymer with styrene end blocks and an ethylene/butylene rubber midblock. The viscoelasticity of this sample has been studied using mechanical rheometry, while in situ SAXS techniques have been used to characterize the way in which applied shear flow perturbs the equilibrium interconnected morphology of this material.