SYNTHESIS AND CHARACTERIZATION OF IMIDE OLIGOMERS END-CAPPED WITH 4-(PHENYLETHYNYL)PHTHALIC ANHYDRIDES

A new series of phenylethynyl end-capped imide oligomers was synthesized and analysed for thermal stability, thermo-oxidative stability, glass transition temperature (T(g)), cure temperatures and adhesive strength. Thus, 4-(phenylethynyl)phthalic anhydride (PEPA) and four substituted PEPAs containing electron-withdrawing groups were synthesized and used as end-capping agents for oligomers of 1,4-diaminobenzene and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. The oligomers underwent an exothermic reaction above 350-degrees-C to afford an insoluble network. The cure reaction was apparently promoted by electron-withdrawing groups as the oligomers end-capped with the substituted PEPAs started to cure at lower temperatures. Their rate of cure was also faster, as evidenced by the faster rise in their T(g)s. The cured resins had T(g)s as high as 405-degrees-C and displayed good thermo-oxidative stability at 371-degrees-C. A cured sample of a PEPA end-capped oligomer with a calculated molecular weight of 4200 g mol-1 displayed moderate high-temperature adhesive strength.