Memory effects in collisional polarization in polystyrene, xylene and polystyrene toluene solutions

Abstract

Far-infrared (10–250 cm^–1) spectra of polystyrene in toluene, m- and p-xylene up to concentrations of 50% w/v are reported. Subtraction of the profiles for the pure components gives an excess loss associated with solvent–polymer collisional polarization. This increases with concentration up to 2%, decreases to 5% and then increases again. It is noted that these concentrations correspond to those at which hydrodynamic screening in the solvent flow velocity distribution starts increasing and then becomes constant, as evidenced in solution viscosity. An explanation of these variations in excess collisional polarization is offered in terms of the way in which the distribution of solvent molecular velocities affects the polarization via translation–vibration excitations. Perturbation of this distribution by prior inelastic collisions with polymer molecules then provides a ‘memory’ effect analogous to hydrodynamic screening.