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

A new series of phenylethynyl end-capped imide oligomers was synthesiz ed and analysed for thermal stability, thermo-oxidative stability, gla ss transition temperature (T(g)), cure temperatures and adhesive stren gth. Thus, 4-(phenylethynyl)phthalic anhydride (PEPA) and four substit uted 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 oligomer s underwent an exothermic reaction above 350-degrees-C to afford an in soluble network. The cure reaction was apparently promoted by electron -withdrawing groups as the oligomers end-capped with the substituted P EPAs started to cure at lower temperatures. Their rate of cure was als o faster, as evidenced by the faster rise in their T(g)s. The cured re sins had T(g)s as high as 405-degrees-C and displayed good thermo-oxid ative 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.