Regiospecific polyamide-imides for gas separations

The separation of gas mixtures by polymeric membranes has become a commercially important methodology for a number of different systems (1). Several recent review articles have discussed the interaction between polymer structure and gas permeability properties (2,3). The quantification of the effect of polymer structure on gas transport properties recently has been reported (4,5) and it is now possible to optimize gas transport properties for well defined polymeric materials. For those materials which do not have a well defined data base it is necessary to prepare and measure the gas transport properties. The polyamide-imides (PAI) are a class of polymeric materials which do not have an extensive data base for gas transport properties (6,7). Work by Yamazaki and coworkers (8) demonstrated that PAI materials could be prepared easily and in a manner whereby the amide bond could be prepared from a phosphite activated carboxylic acid and an aromatic amine. Yang and CO workers (9-11) have shown that novel dicarboxyl ic acids could be prepared from trimellitic acid anhydride (TMA) and aromatic diamines and that these dicarboxylic acids could be coupled with a second diamine to form regiospecific PAI materials. Our focus was to examine the effects of a phenylene diamine and its alkylated analogs on the gas transport properties of regiospecific PAI materials and to identify those structures which maximized both permeability and selectivity. 

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