SynopsisThe free-volume theory describing diffusion in polymer-solvent systems is reexamined. Calculation of the specific free volume for such systems is discussed, and equations are presented for the determination of the self-diffusion coefficients of the polymer and the solvent. Conditions under which the mutual diffusion coefficient can be deduced solely from free-volume considerations are clarified, and a more general version of the free-volume diffusion theory proposed by Fujita is presented. The further restrictions needed for the theory of Fujita are discussed, and it is concluded that these additional restrictions are responsible for failures of the Fujita theory.

A new free‐volume theory is combined with the thermodynamic theory of Flory and the entanglement theory of Bueche to provide a means of predicting the temperature, concentration, and molecular weight dependence of mutual‐diffusion coefficients in amorphous polymer–solvent systems. The predictions of the theory are compared with actual data for the ethylbenzene–polystyrene system.

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A revised version of a recently proposed free‐volume theory of polymer‐solvent diffusion is introduced and evaluated using experimental diffusivity data collected over wide temperature and concentration ranges. The theory accurately predicts the large temperature and concentration variations typically observed for polymer‐solvent diffusion coefficients.

H P = 0.0015607 I; T In( Pout/Pin) OP = annual operating cost, $/yr. ;tic fluids, it is reasonable to expect that a diffusion Deborah number can be defined which corresponds to the Deborah number used to characterize flow of polymeric materials. In this paper we propose a Deborah number which can be used to characterize diffusional transport in amorphous polymer-solvent systems and consider the calculation and utilization of this dimensionless group. Deborah number is demonstrated by using this dimensionless group to anticipate conditions under which thicknezs anomalies can be expected in sorption experiments for the atactic polystyrene-pentane system.Investigations of diffusion phenomena in amorphous polymer-solvent systems have shown that it is possible to observe widely differing behavior by traversing a large enough range of temperature, concentration, and polymer molecular weight. Alfrey ( 1965) and Hopfenberg and FriscEi (1969) depicted the different types of diffusional transport of penetrants in higll polymers by utilizing a tcmperature-penetrant concentration diagram. It was later noted (Duda and Vrentas, 1970) that the various regions on this diagram could be distinguished by the ratio of two characteristic times, a cliaracteristic relaxation time for the