Critical conditions for structure formation in semidilute polymer solutions induced under continuous shear flow

Publisher Website
Google Scholar
Abstract
Critical conditions for shear-induced structure formation in semidilute polystyrene solutions with dioctyl phthalate as a solvent are studied by light scattering and rheological measurement. The critical shear rate γ̇cx for the onset of the nonlinear enhancement (defined in the text) of the concentration fluctuations are investigated as functions of temperature and concentration. γ̇cx increases with increasing temperature or decreasing concentration, reflecting the temperature and concentration dependence of the thermodynamic and viscoelastic properties. This temperature and concentration dependence of γ̇cx was found to be in parallel to that of the critical shear rate for the onset of the linear enhancement (also defined in the text) of the concentration fluctuations, which can be explained in terms of a linear theory proposed by Onuki. The critical shear stress and the critical first normal stress difference corresponding to γ̇cx are also explored, the physical interpretation of which will be discussed in detail in conjunction with the stress components arising from anisotropic concentration fluctuations, based on the calculation by van Egmond.