Membrane Gas Separation

2.7
Conclusions 
A variety of techniques, including gas adsorption, computer simulation, inverse gas chro-
matography and positron annihilation lifetime spectroscopy, all support the assertion that 
PIM - 1 behaves like a molecular sieve, with effective pores of dimensions
<
2 nm (i.e. 
micropores as defi ned by IUPAC). This, combined with its chemical structure, which 
includes both aromatic rings and highly polar nitrile groups, gives rise to extraordinarily 
high solubility coeffi cients for a wide range of gases and vapours, which in turn results 
in membranes with an exceptional combination of permeability and permselectivity for 
a number of important gas separations. Strongly interacting solutes can profoundly affect 
transport properties, so that water - treated membranes have reduced permeability but a 
methanol treatment can substantially enhance permeability.
Acknowledgements 
This collaboration was made possible by support from INTAS (Project 05 - 1000008 -
7862). The UK participants thank EPSRC for funding.
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