Temperature Dependence of the Soret Motion in Colloids.

We discuss thermally driven transport in both organic solvents and electrolyte solutions and, in particular, the variation of the thermophoretic mobility DTwith temperature. We find that the T-dependence in organic solvents arises from the viscosity η(T), in qualitative agreement with data on polystyrene in ethylbenzene. A more subtle effect occurs for charged colloids in an electrolyte, where the strong correlation of DTwith the thermal expansivity β of water is traced back to the thermoelectric effect. Our results provide an explanation for experiments on various colloidal suspensions and, in particular, for the observed change of sign of DTas a function of temperature. [ABSTRACT FROM AUTHOR]