Chain-extendable polyimide precursors based on oligoamic acid derivatives

Abstract

A number of different pyromellitic dianhydride (PMDA)/p,p'-oxydianiline (ODA) based polyamic acid alkyl esters have been synthesized and characterized with respect to their imidization behavior. It was found that these materials did indeed imidize at higher temperatures than the corresponding amic acid. This behavior closely tracks the observed reactivity of the corresponding PMDA alkyl diester diacids toward ring closure, i.e. anhydride formation, at elevated temperatures which increases with the acidity of the parent alcohol. The increase in imidization temperature, in some cases by as much as 100°C, allows for much greater flexibility in the type of chain extender employed and leads to greatly improved, chain-extendable polyimide precursor formulations. The synthesis and characterization of various amine-terminated oligoamic alkyl esters in conjunction with chain extenders based on different aromatic dianhydride derived dialkylester diacids to prepare high solids content polyimide formulations is discussed.