Chemistry and Characterization Of Polyimides Derived from Poly(Amic Alkyl Esters)

ABSTRACTThe modification of the pendant acid groups along the poly(amic acid) backbone in the form of alkyl ester groups leads to greatly improved polyimide precursors. These poly(amic alkyl esters) are characterized by the absence of hydrolytic instability due to elimimation of the “monomer-polymer” equilibrium associated with poly(amic acids), a broad imidization temperature regime, improved solubility characteristics, and enhanced mechanical properties. In the absence of hydrolytic instability, it is now possible to use an aqueous work-up of the polyimide precursor. This presents an attractive synthetic pathway for the preparation of well-defined, amine-terminated oligomers. Such oligomers can then be utilized both in the preparation of low molecular weight, chain-extendable polyimide precursors as well as polyimide block copolymers. The higher imidization temperatures offered by the “amic ester” chemistry allows for more efficient chain extension prior to imidization. Alternatively, the lack of the “monomer-polymer” equilibrium and accompanying propensity for monomer randomization reactions presents a potential pathway for the preparation of polyimide blends.