ELECTROOPTICS OF SEMIDILUTE DISPERSIONS - INFLUENCE OF ELECTROSTATIC INTERACTIONS ON COLLOID PARTICLE RELAXATION LIMES

The variation of the electro-optic decay times with the intensity and frequency of the applied electric field are investigated for a colloid system of rigid rod-like particles. In the kilohertz frequency range the decay process is consistent with field-free Brownian disorientatio n and the time constants are sensitive to interparticle electrostatic interactions. The abrupt rise in the electro-optic relaxation times ac companied by a decrease in the saturation value of the effects, observ ed in the process of deionization of the medium, indicates a phase tra nsition from a gas to a liquid-like state of the colloid system. At lo w frequencies (hertz range and de pulses) the decay times are reduced by an additional effect, most probably of a hydrodynamic nature. (C) 1 995 Academic Press, Inc.