Journal of Chemical Physics, Vol.100, No.4, 3224-3232, 1994
A Neutron-Scattering Study of Shear-Induced Turbidity in Polystyrene Dissolved in Dioctyl Phthalate
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 (gamma equal to or greater than 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 how direction is distorted and the scattering data normal to how 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.
Keywords:ENHANCED CONCENTRATION FLUCTUATIONS;SEMIDILUTE POLYMER-SOLUTIONS;INDUCED DENSITY GRADIENTS;INDUCED PHASE-SEPARATION;CRITICAL SOLUTION POINT;LIGHT-SCATTERING;PRESSURE-DEPENDENCE;INDUCED DEFORMATION;CRITICAL FLUIDS;DILUTE-SOLUTION