Ordered structure and critical phenomena of a semidilute solution of polymer mixtures under shear flow

Abstract

A semidilute solution of a polymer mixture with a nearly critical composition was studied by using the small-angle light scattering method as a model system to study ordered structures and critical phenomena of mixtures under shear flow. The experimental studies revealed that there are five regimes in the shear-rate dependence of the concentration fluctuations of the solution, as discussed in the text, including the regime in which the ‘‘shear-induced homogenization’’ takes place. The results were interpreted, as much as possible, with the theories developed for binary mixtures of simple liquids and, when necessary, with a theory proposed here for polymer systems. Unique features of polymer dynamics in comparison with the dynamics for the critical mixtures of simple liquids were presented in the text, e.g., the shear-rate (S) dependence of the cutoff wave number being proposed to be given by qc,S∼(Dcξ20)−1/4 S1/4 rather than qc,S∼(6πη/kBT)1/3S1/3 for the simple liquids.