Diffusion of benzene vapor in blends of poly(vinyl acetate) and poly(methyl acrylate)



Sorption and diffusion of benzene in miscible blends of poly(vinyl-acetate), PVAc, and poly(methyl acrylate), PMA, have been studied. The polymer-polymer interaction parameter values calculated from equilibrium vapor sorption data were all negative, indicating favorable interaction between the two polymers. The sorption of benzene vapor into these blends was measured at a temperature above the Tg's of the pure polymers and found to obey Fickian kinetics. The mutual diffusion coefficients were estimated from the initial slopes of the sorption curves. The concentration dependent diffusion coefficients were fitted to the empirical relation D = Do exp(αC) which satisfactorily correlated the data. Values of the constant Do were found to vary continuously with blend composition, while the α values did not. These experimental data were analyzed employing Fujita's free volume theory. It was found that the data was consistent with this theory. If the fo values for the blends are assumed to be the weighted average of the component polymers, then the β parameter values for the blends also obey the additivity rule.