AbstractUsing the Gibbs description of surfaces, a sorption model is developed which describes sorption isotherms for such systems as water in polymers. Moreover, the Freundlich isotherm for monolayer sorption is obtained. The physical interpretation of the constants of the model and the boundary conditions required for application to sorption isotherms are discussed. On basis of the Freundlich isotherm, a multilayer model is proposed to describe the water sorption in polymers. Experimental results within the whole range of relative humidity are found to be in excellent agreement with the multilayer model. Disagreement between model isotherm and experimental data of some polymers at relative humidities above 90 might be due to capillary phenomena not considered in the present model description.
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