A GENERALIZED FORM OF THE LANGMUIR ISOTHERM FOR GAS-ADSORPTION IN GLASSY-POLYMERS

Glassy polymers contain sites where excess free volume makes adsorptio n of gases possible; they also contain sites where ordinary absorption governed by Henry's law can occur. In this paper, we analyze the poss ibility of a continuous distribution of site types, characterized by v alues of adsorption capacity, affinity constant, and sorption constant which span a continuous range. Experimental data are easily fitted wi th great accuracy by the resulting equations; indeed, different sets o f parameter values may fit any given set of data equally well, indicat ing that evaluation of parameter values from experiments should be reg arded with careful skepticism.