Rubbery polymers sorption theory

This review does not aim for an encyclopedic coverage of the rapidly expanding field of membrane science. The topics treated do, however, present a reasonable sampling of the current literature on membrane science. The subfects treated reflect directly the interests of the authors and many of the topics are fundamentally related to the fact that the membrane is a high polymer. Indeed, the transport and sorption theories presented provide parameters whose physical interpretation often is a useful complement to other methods of physical analysis of the polymeric state. The study of gas sorption and transport in rubbery polymers is petbaps the simplest example of such a case and will be treated first. 

The solubility of hydrocarbons in rubbery polymers can be described in more detail by several theories of solutions using various criteria of thermodynamic affinity [7,25-28], of which the Flory-Huggins theory is the most popular one. It takes into account the volume content of the penetrant dissolved in the polymer and the change in the length of the polymer s thermodynamic segment as a result of dissolution [7]. However, it should be pointed out that to describe dissolution, a rehned dual-mode sorption model can be used, e.g., the model by Pace and Datyner [7,29,30]. 

While the permeability of most rubbery polymers to most gases is pressure independent, the permeability of glassy polymers usually is observed to decline with increasing pressure. This is accounted for by the dual sorption theory if one assumes that both the Henry and Langmuir type sites contribute to per-... 

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