Thermophoresis of thermoresponsive polystyrene-poly(N-isopropylacrylamide) core-shell particles

We have investigated diffusion and thermodiffusion of thermosensitive core-shell particles (PS-PNIPAM) that consist of a poly(styrene) (PS) core and a poly( N -isopropyl acrylamide) (PNIPAM) shell by means of an optical beam deflection technique. The results are compared to recent literature values for linear PNIPAM chains and cross-linked PNIPAM microgel particles. The temperature dependence of the thermodiffusion coefficient of the core-shell colloids resembles that of the linear polymer and a number of other aqueous systems. It is significantly different from one of the crosslinked microgels. Thermophoresis of thermoresponsive PS-PNIPAM core-shell particles differs distinctly from that of the PNIPAM microgels and resembles the behaviour of the linear polymer.