Abstract A new method for linear polymerization of maleimides via the Diels–Alder reaction has been developed. This method involves use of a new cross-linking agent, benzene-3, 4- dimethylenesuccinimide, which can be generated in situ from its thiophene precursor, benzene-2, 5-dihydrothiophene-3, 4-dicarboximide-S, S-dioxide. This new cross-linking agent is reasonably reactive, readily prepared, and stable at room temperature. A ...