Shear-Induced Structures in Semidilute Polystyrene Solution: Effect of Solvent Quality

Abstract

The effect of solvent quality on shear-induced structures in semidilute polystyrene solutions are investigated by using light-scattering and rheological methods. We found that the shear-induced structures are universally formed in various solvents employed in this experiment. We especially focus on a critical shear rate γ̇cx, at which the light scattering intensity starts to increase in our experimental geometry, and on a critical shear stress, σxy,cx, at γ̇ = γ̇cx. We found that γ̇cx is not well correlated with χ but rather that σxy,cx is better correlated with χ, where χ is the Flory−Huggins interaction parameter between polystyrene and solvents. σxy,cx increases with decreasing χ. This indicates that the structure formation is strongly affected by solvent quality, mainly through the thermodynamic state of the solution. We also analyzed the solvent quality dependence of γ̇cx in the context of Onuki's linear theory, and found that γ̇cx can be scaled by Kos/η0, where Kos is the osmotic modulus and η0 the zero-shear viscosity.