Synthesis and gas transport properties of random amide imide copolymers

Fully imidized random amide imide copolymers (rPAI) can be prepared in an a protic solvent from trimellitic anhydride chloride (TMAc) and mixtures of v arious aromatic diamines via condensation polymerization. The polymers are soluble in a number of aprotic organic solvents including 1-methyl-2-pyrrol idinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), a nd dimethylsulfoxide (DMSO). The gas transport properties of the rPAI mater ials are governed by the local structure around both the amide and imide li nkages and can be tuned by the choice and ratio of diamines used. Significa nt improvement in selectivity relative to polyimides can be achieved. When inorganic carbonate salts are used to scavenge byproduct hydrogen chloride, the amount of residual salt in the dense films has a substantial effect on their gas transport properties. A fugitive salt process tvas identified, w hich eliminated this problem of residual inorganic salts. The activation en ergy for O-2, N-2, He, CO2, and CH4 permeability was determined for one of the copolymers. (C) 2000 John Wiley & Sons, Inc.