Synthesis of novel non-glycidyl ether epoxy resins the Corey–Chaykovsky reaction and preparation of high heat-resistant cured products by their curing reaction

In this study, three types of non-glycidyl ether epoxy resins, namely, 2,2′-(1,4-phenylene)bisoxirane (PBOX), 1,7-dioxadispiro[2.2.2.2]decane (DCD), and 1,1′-dioxa-6,6′-bispiro[2.5]octane (DBO), were synthesized via a peroxide-free route using the Corey–Chaykovsky reaction between carbonyl compounds and methylsulfonium methylide. Differential scanning calorimetry measurements indicated that the reactivity of PBOX was comparable to that of its glycidyl ether analogue and that DCD and DBO have larger strain energy than their glycidyl ether counterparts. The non-glycidyl ether epoxy resins were found to be curable with phenol novolak and m-phenylenediamine (MPDA) as curing agents, and the thermal stability of the resulting cured products was compared with that of the corresponding glycidyl-ether-type cured derivatives. The PBOX-derived cured product exhibited higher physical thermal stability than its glycidyl ether counterpart, and the DCD- and DBO-derived cured products showed higher physical/chemical thermal stability than the corresponding glycidyl ether cured derivatives. The DBO-derived cured product showed the highest thermal stability among the compounds evaluated, with a 5% weight loss temperature of 408 °C and a glass transition temperature of 291 °C. These results suggest that non-glycidyl ether epoxy resins are promising highly heat-resistant thermosetting resins suitable for various applications, such as encapsulation of next-generation power devices for high-temperature operation.