Shear SANS Study of Entangled Polymer Solutions

In situ small angle neutron scattering and rheological measurements have been carried out on entangled polybutadiene solutions in simple shear flow in a Couette shear cell (SANS) and cone/plate cell (rheology). Stable shear flow has been achieved over a range of shear rates covering the stress plateau, at which polymer chains are expected to partially disentangle [1]. Shear-induced structure was recorded in both the flow-vorticity and gradient-vorticity planes. The data appeared to imply the absence of ensemble averaged large chain deformation in steady state, whereas geometrical scaling analysis suggested that chain stretching could occur locally. [1] Tapadia, P.; Wang, S. Q. Macromolecules, 37, 9083 (2004).