DIELECTRIC RESPONSE MEASUREMENTS ON CONCENTRATED COLLOIDAL DISPERSIONS

We investigated the low-frequency dielectric response of colloidal suspensions of a monodisperse latex suspended in mM KCI. Measurements were made at frequencies between 500 and 200 kHz with particle concentrations up to 30% (vol.) using a four-electrode cell. Particle mobility and static conductivity were also measured to test the consistency of theoretical models. With dilute systems, neither the standard electrokinetic model nor models with surface transport could be used to interpret the data in an internally consistent fashion. Nevertheless, we found empirical formulas correlated the data over the whole range of particle concentrations. Maxwell's equation was used for the static conductivity and the Cole-Cole expression could be used for the frequency-dependent dielectric constant. (C) 1995 Academic Press, Inc