A neutron scattering study of shear induced turbidity in polystyrene dissolved in dioctyl phthalate

Abstract

The influence of shear on the small angle neutron scattering from a semidilute solution of polystyrene (PS) dissolved in dioctyl phthalate (DOP) is examined in the limit of strong shear (γ̇≥100 s⁻¹). These experiments are restricted to room temperature, which is close to the theta point of PS/DOP. The fraction of deuterated PS chains is varied, while the total polymer weight fraction is fixed at 3%. This is near the critical composition of hydrogenated PS in DOP. The increased scattering at high shear rates (‘‘shear induced turbidity’’) is interpreted in terms of a critical temperature shift. Scattering along the flow direction is distorted and the scattering data normal to flow is uninfluenced by shear above a wave vector cutoff q*, which is independent of shear rate. This cutoff is found to correspond to the Debye length, characterizing the average intermolecular potential range.