Collect. Czech. Chem. Commun. 1985, 50, 2364-2368

Contribution to the theory of nonfickian diffusion of gas in a polymer

Ivan Samohýl, X. Quang Nguyen and Milan Šípek

Department of Physical Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6


Based on the previous work on rational thermodynamics of a fluid-solid mixture in linear approximation, an expression for the diffusion flux was derived. This (with tensor phenomenological coefficients) depends linearly on the temperature gradient and on the isothermal gradient of chemical potential, hence not only on the gas concentration gradient but also on the second deformation gradient of the polymer and on the gradient of the internal parameter (characterizing long-term memory effects in the polymer). Nonequilibrium values of the internal parameter may cause a diffusion flux also directly. However, this is not the case in an isotropic solid or fluid polymer, where the tensor phenomenological coefficients and thus also the diffusion coefficient are reduced to scalars. The results are discussed in relation to the classical diffusion in fluids.