DIELECTRIC RESPONSE MEASUREMENTS ON CONCENTRATED COLLOIDAL DISPERSIONS

We investigated the low-frequency dielectric response of colloidal sus pensions of a monodisperse latex suspended in mM KCI. Measurements wer e made at frequencies between 500 and 200 kHz with particle concentrat ions up to 30% (vol.) using a four-electrode cell. Particle mobility a nd static conductivity were also measured to test the consistency of t heoretical models. With dilute systems, neither the standard electroki netic model nor models with surface transport could be used to interpr et the data in an internally consistent fashion. Nevertheless, we foun d empirical formulas correlated the data over the whole range of parti cle concentrations. Maxwell's equation was used for the static conduct ivity and the Cole-Cole expression could be used for the frequency-dep endent dielectric constant. (C) 1995 Academic Press, Inc