A Physical Chemistry seminar by Professor Jan Dhont, Research Center Jülich, Germany

Title: Temperature-Induced Migration of Uncharged Interacting Macromolecules

Abstract: Migration of molecules induced by temperature gradients is commonly referred to as thermophoresis, thermodiffusion, thermal diffusion, or the (Ludwig-)Soret effect. The thermophoretic force experienced by a macromolecule (like a colloidal particle) that drives thermodiffusion consist of two distinct contributions: a contribution resulting from internal degrees of freedom of single colloidal particles (for example due to an electric double layer), and a contribution due to the interactions between the colloids. An irreverible thermodynamics-based theory will be discussed for the latter collective contribution to the thermophoretic force. The present theory leads to a novel "thermophoretic interaction force", which has not been considered in earlier approaches. This force will be shown to be essential to describe data on a sticky hard sphere suspension. The experimental method to obtain these data is commonly referred to as TDFRS (Thermo Diffusion Forced Rayleih Scattering), the principle of which will be briefly explained.