Comparative study on polyimides derived from isomeric diphenylsulfonetetracarboxylic dianhydrides

Abstract

In this study, three diphenylsulfonetetracarboxylic dianhydride (DSDA) isomers namely 2,2′,3,3′-DSDA (3,3′-DSDA), 2,3,3′,4′-DSDA (3,4′-DSDA) and 3,3′,4,4′-DSDA (4,4′-DSDA) were prepared from the corresponding diphenylthioethertetracarboxylic dianhydride isomers. Based on the three DSDA isomers, a series of isomeric polyimides were prepared. The properties, such as film-forming ability, solubility, wide-angle x-ray diffraction, thermal and mechanical properties as well as rheological behavior, were compared among the isomeric polyimides. It was found that 4,4′-DSDA-based polyimides had much better film-forming ability than 3,3′-DSDA- and 3,4′-DSDA-based polyimides. 3,4′-DSDA-based polyimides had better solubility than 3,3′-DSDA- and 4,4′-DSDA-based polyimides. Furthermore, for a given diamine, the glass transition temperatures of the polyimides from the three DSDA isomers decreased in the order of 3,3′-DSDA > 3,4′-DSDA > 4,4′-DSDA, while the 5% weight loss temperatures in both air and nitrogen atmospheres of the polyimides mainly increased in the order of 3,3′-DSDA < 3,4′-DSDA < 4,4′-DSDA. Moreover, 3,4′-DSDA- and 4,4′-DSDA-based polyimides showed much better melt stability than 3,3′-DSDA-based polyimide.