MEASUREMENT OF SORPTION IN POLYMER MEMBRANES WITH A QUARTZ CRYSTAL MICROBALANCE

An application of the oscillating quartz crystal microbalance (QCM) in the measurements of sorption rates and equilibria in polymer-vapor systems is presented. The sorption isotherms of methanol, ethanol and n-heptane in cellulose acetate and poly(hexamethylene adipamide) were measured with the QCM at 298 K. The results agree reasonably with the Flory model except at low absorbate activities where appreciable deviations due to localized absorption were observed, as verified with IR spectroscopy. The diffusion coefficient of methanol in cellulose acetate was also calculated from the sorption rate data measured with the QCM.