Study of temperature dependence of thermal diffusion in polystyrene/ethylbenzene by thermal field‐flow fractionation

Using a special thermal field‐flow fractionation apparatus capable of working over a broad temperature range, we have observed that retention in the polystyrene/ethylbenzene system decreases substantially as the cold wall temperature increases from 360 to 424 K. Polymers of four different molecular weights ranging from 20,000 to 160,000 were used to verify this conclusion. Based on our earlier work showing that thermal diffusion parameters could be calculated from retention data, we have used the present measurements along with earlier values to generate a compilation of thermal diffusion data over the temperature range from 270 to 424 K. These results are used to develop empirical expressions for the thermal diffusion factor and the thermal diffusion coefficient for polystyrene in ethylbenzene as a function of temperature and molecular weight. It is shown that these results have potential usefulness both in terms of the new physicochemical data obtained and in terms of the guidelines they provide for choosing experimental conditions for thermal field‐flow fractionation experiments.