THERMOGRAVITATIONAL THERMAL-DIFFUSION IN LIQUID POLYMER-SOLUTIONS

We analyzed the steady state behavior of a thermogravitational column for a toluene-polystyrene system at different concentrations and at mo lecular weights of polystyrene in the 45 000-540 000 range. The result s obtained indicate that steady state separation strongly increases wi th concentration and molecular I weight. From steady state separation measurements, the thermal diffusion coefficient of the mixtures consid ered was determined. It is shown that this quantity is in the dilute r egion, irrespective of molecular weight and concentration. The close a greement between our values and those reported in the literature obtai ned using different techniques indicates that closed columns can be us ed to accurately determine thermal diffusion properties of macromolecu lar solutions.