Diffusion in Glassy Polymers. III. Temperature Dependence and Solvent Effects

Absorption and desorption of benzene and ethyl acetate by atactic polystyrene (A-PS) were studied at various temperatures below the glass transition point of the polymer. In the A-PS+ benzene system raising temperature did not alter the general feature of the family of successive differential absorption curves, but merely compressed the whole family of curves towards a low concentration region. The critical concentration of penetrant at which the transition from non-Fickian to Fickian behavior occurred became lower in the order benzene, ethyl methyl ketone, and ethyl acetate. The logarithm of the time, t*, which specifies the inflection point of the second stage on the two-stage absorption curve, were linearly dependent on the initial concentration of penetrant, Ci, and the correlation lines between log t* and Ci obtained for various combinations of temperature and solvent were nearly parallel with one another. The features of integral absorptions were essentially the same in all cases, and the absorption curves showed a pronounced dependence on concentration.