Copolymers derived from bismaleimide oligomer with active solvent

An oligomer from 4, 4′‐bis(maleimido)diphenyl methane and methylenedianiline were dissolved in active solvent N, N ‐dimethyl acrylamide in a solid content up to 50–70%; the solution was poured in a sheet‐shaped module and irradiated by 60 Co with the dose from 20 to 350 kGy at room temperature. The polymerized sheet was postcured at 180°C to obtain a transparent red‐orange sheet with tensile strength above 100 MPa. The glass transition temperature before and after postcuring was around 100°C and 150–180°C, respectively. Styrene was used along with DMAA to decrease the water absorption for the copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2879–2882, 2004