EQUATION RELATING SELF-DIFFUSION AND MUTUAL DIFFUSION-COEFFICIENTS IN POLYMER-SOLVENT SYSTEMS

An equation which relates the mutual diffusion coefficient in a polymer-solvent system to the self-diffusion coefficient of the solvent and to the thermodynamic properties of the mixture is proposed and tested. The validity of the equation is checked by collecting mutual diffusion, self-diffusion, and thermodynamic data for the polystyrene-toluene system at 110 °C. A new apparatus has been constructed for measuring self-diffusion coefficients for polymer-solvent systems at elevated temperatures. It is concluded that the equation is valid for at least 75% of the mass fraction interval for the toluene-polystyrene system and that similar behavior should be expected for other amorphous polymer-solvent systems. © 1979, American Chemical Society. All rights reserved.