A Group Contribution-Based Model to Predict Organic Solvent Diffusivities in Amorphous Rubbery Polymers

A modified free-volume model was developed to predict solvent diffusion coefficients in amorphous rubbery polymers, with the introduction of the Sanchez-Lacombe equation-of-state (EOS) into the free-volume theory. The characteristic parameters of the EOS are the only introduced parameters, and they can be determined with the knowledge of polymer structural units. Since all of the parameters with respect to the polymer can be determined by the group contribution method, this model provides feasibility to correlate the solvent diffusivities with polymer structures, without the knowledge of any diffusion or viscoelastic data. The calculations of infinite dilution diffusion coefficients and solvent self-diffusion coefficients for seven kinds of organic solvents in seven kinds of polymers were generally consistent with the published experimental results.