Synthesis and Thermal Cure of Anthracenyl−Ethynyl End-Capped Imide Oligomers

The model compound, N -phenyl-4-(9-anthracenylethynyl)phthalimide ( 3 ), was synthesized and the thermal curing behavior analyzed. These results were compared to the curing kinetics of similar model compounds N -phenyl-4-(1-naphthylethynyl)phthalimide ( 1 ) and N -phenyl-4-phenylethynylphthalimide ( 2 ). The cure rates are found to increase in the order of phenyl < naphthyl ≪ anthracenyl with indistinguishable E a values for 1 and 2 . Compound 3 showed a slightly lower E a for the curing process. The end-capping reagent 4-(9-anthracenylethynyl)phthalic anhydride (4-AnEPA, 4 ) was prepared and used to synthesize an “anthracenyl−ethynyl terminated imide oligomer” (AnETI- 5 ) and a lower T g anthracenyl−ethynyl terminated imide- co -oxydiphthalic anhydride oligomer (AnETI- 5 -ODPA). Kinetic data for the thermal cure of the oligomers were measured by monitoring the change in T g and applying the DiBenedetto equation. To ensure consistency, the thermal cure kinetics of phenyl−ethynyl terminated imide oligomer (PETI- 5 ), naphthyl−ethynyl terminated imide oligomer (NETI- 5 ), and phenyl−ethynyl terminated imide- co -oxydiphthalic anhydride oligomer (PETI- 5 -ODPA) were co-analyzed. The T g observed for the cured resins was found to be independent of the end-cap type. However, the new aryl−ethynyl end caps provide significant thermal cure rate acceleration, often without a change in the E a . For example, the anthracenyl−ethynyl end-capped oligomers can be cured at the same rate as the phenyl−ethynyl analogue; however, at a temperature nearly 80 °C lower!