High-Temperature Thermosets Derived from the Diels-Alder Polymerization of Bisbenzocyclobutenes and Bimaleimides

A number of compatible mixtures of 2,2-bis4-N-4-benzocyclobutenyl phthalimide-4-phenyl hexafluoropropane BCB and 1,1-methylene di-4, 1- phenylene bismaleimide BMI were prepared. Complete compatibility of the mixtures was evidence by a single initial t sub g. All mixtures showed relatively low initial t sub gs and characteristic polymerization exotherms of benzocyclobutene-based systems providing and excellent processing window. The cured sample of the mixtures, pure BCB and BMI were subjected to comparative isothermal gravimetric analysis ITGA. After 200 hours at 650 F 343 C in circulating air, the cured BMI exhibited similar thermo-oxidative stabilities to BCB. A model compound was synthesized from the intimate mixture of N-phenyl maleimide and N-benzocyclobutenyl phthalimide in 63 recrystallized yield. The ITGA results and isolation of the model Diels-Alder adduct render strong support to the conviction that Diels-Alder polymerization is the predominant curing process in the BCBBMI system.