INFLUENCE OF THE GLASS-TRANSITION ON SOLUTE DIFFUSION IN POLYMERS BY INVERSE GAS-CHROMATOGRAPHY

The capillary-column inverse gas chromatography (CCIGC) method was use d to determine diffusivity data for several solvents in poly(styrene) at conditions approaching infinite dilution of the volatile component. Measurements were made over a temperature range traversing the polyme r glass transition temperature. The chromatographic data were analyzed by employing the elution model developed by Pawlisch et al. The Vrent as-Duda free-volume theory of diffusion was utilized to correlate the diffusion data and to interpret the effect of the glass transition tem perature on the diffusion coefficient and on the effective activation energy in the limit of zero penetrant concentration. The free-volume t heory was found to correlate the diffusion data very well. The results of this study confirmed the free-volume concept that molecular diffus ion is not as inhibited as one might expect below the glass transition temperature of the polymer.