KINETICS OF MASS-TRANSFER IN POLYMERS WIT H COMPLEX SUPERMOLECULAR STRUCTURE

The kinetics of sorption, proceeding according to the mechanism of par allel diffusion, is investigated. This mechanism is supposed to accoun t for mass transfer in polymers with complex supermolecular structure, where each particular structural unit is described by-an intrinsic di ffusion coefficient. The apparent diffusion coefficient is function of time D(t), By means of the initial absorption rate and the initial va lue of the diffusion coefficient D(0), one can determine-the average d iffusion coefficient and the ultimate concentration of the sorbate, wh ich differ depending on the type of averaging. These averages make it possible to refer the deviations in sorption kinetics from Fick's law to inhomogeneities present in the supermolecular structure of the poly mer or to other causes (e,g., to relaxation of the system).