Polyimide membranes derived from poly(amic acid) salt precursor polymers. 1. synthesis and characterization

A series of new poly(amic acid) salt polymers were synthesized and characterized. It has been found that these poly(amic acid) salt polymers are highly soluble in alcohol-based solvents, a feature that is useful for membrane preparation. It was also found that poly(amic acid) tertiary amine salts can be quantitatively imidized at 150 degreesC, a temperature that is lower than the imidization temperature of poly(amic acid) or of poly(amic acid) quaternary amine salts of identical backbone structure. This makes poly(amic acid) tertiary amine salt polymer a preferred precursor for preparation of polyimide gas separation membranes. Gas permeation characteristics of dense polyimide films prepared from poly(amic acid) tertiary amine precursors were further measured and compared to chemically identical polyimide films obtained by conventional methodologies.