Characterization of a soluble polyimide

The solid phase thermal imidization of a soluble 4,4-prime-bis (3,4-dicarboxyphynoxy) diphenyl sulfide dianhydride plus 2,2-bis 4-(4-aminophenoxyl)phenyl hexafluoropropane (BDSDA-BDAF) polyimide precursor staged between 40 and 325 C was characterized by gel permeation chromatography, inherent viscosity, and number average molecular weight measurements. The information obtained indicated that this polyamic acid experienced an initial reduction in molecular weight during cure before achieving its ultimate molecular weight as a polyimide. The event was most likely related to the development of an anhydride band that appeared in the infrared spectrum around 1850/cm as the material cured. Correlation through infrared spectroscopy with a previous study dealing with several common, but insoluble, polyimide precursors, suggested that polyimides, in general, exhibit this trend in molecular weight behavior.