Solubility and Diffusion Behavior of Benzene in a Vinyl Acetate‐Methyl Acrylate Copolymer

Equilibrium sorption and the kinetics of sorption of benzene have been obtained in a 46% vinyl acetate‐54% methyl acrylate copolymer at temperatures from 25 to 55°C. and at equilibrium concentrations up to 0.19 volume fraction of benzene (V). The ther‐modynamic diffusion coefficient (Dt) obtained from the sorption rates can be fitted by a relationship of the kind suggested by Wilkens and Long: In Dt = In Do + AV ‐ BV2 but the data are not accurate enough for the A/B ratio to give useful information about the system. By using suitable values for Ao and Bo the relationship Dt = RT/Ao exp { ‐Bo/fv} due to Fujita enables the temperature and concentration dependence of the free volume fv to be calculated. The resulting relationship fv = 0.025 + 0.00043[T ‐ (21 ‐ 280V)] suggests a glass transition of 21°C. for the copolymer. The Flory‐Huggins interaction parameter x is calculated from the equilibrium data and the figure obtained, 0.36, is much closer to the value for polyvinylacetate than to polymethylacrylate. This is also true of the Do values.