Rubbery polymers size selectivity

CO2 separation by using a membrane prepared from a rubbery polymer is based on high solubility selectivity, while diffusivity selectivity should be maintained or even increased. The CO2/H2 permselectivity is increased (due to the inaeased EO units), which is a consequence of solubility selectivity increase. The strategy of increasing the solubility plays an important role, because of the unfavourable diffusivity selectivity. Incorporation of PEG increases the permselectivity of the pair CO2/H2 to 13. However, the CO2/N2 and CO2/CH4 permselectivities are maintained almost constant due to the similar penetrants size. 

Epoxy resins are toughened with functionally terminated liquid polymers. Small rubbery domains of a definite size and shape are formed in situ during cure. The selectivity and reactivity of the functional groups of liquid polymers are critical for the in situ formation of rubber particles. 

Glassy polymers are inherently more size and shape seiective than rubbery materials. This additional mobility selectivity arises from the restrictive nature of transport in glassy environments, which are characterized by extremely limited segmental motions. Because of their large potential for use as monolithic membranes and selective coatings on composite membranes, a fairly detailed discussion of the sorption and transport behavior of glassy polymers is presemed in the following section. 

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