Free‐volume theories for self‐diffusion in polymer–solvent systems. II. Predictive capabilities

The predictive and correlative capabilities of two recent versions of the free‐volume theory for self‐diffusion in polymer–solvent systems are examined by comparisons with experimental data. Neither the Vrentas–Duda free‐volume theory nor the Paul version generally provides satisfactory predictions for the temperature and concentration variations of solvent self‐diffusion coefficients. However, the Vrentas–Duda theory does provide good correlations of solvent self‐diffusion data, and, furthermore, this theory can provide good predictions if a small amount of solvent self‐diffusion data is used to help estimate the parameters of the theory. New diffusivity and equilibrium data were collected for the toluene‐PVAc system to provide a broader database for evaluation of the self‐diffusion theories.