High performance thermosetting bismaleimide resins via thiol-maleimide "click" reaction

A telechelic thiol functionalized poly(p-phenylene sulfide) oligomer (SPPSO) was prepared by the reaction of 1,4-dichlorobenzene and excess sodium sulfide. 4,4'-Bismaleimidodiphenylmethane (BMI) was prepolymerized with various molar ratios of SPPSO, a pentaerythritol-based tetrathiol (S4P) and an isocyanurate-based trithiol (S3I) at the maleimide/SH ratio of 1/1 at 200 degrees C in the presence or absence of dimethylphenylphosphine (Me2PPh) and then compression-molded at finally 210-230 degrees C to produce cured resins (BMI-SPPSO, BMI-SPPSO/S4P, BMI-SPPSO/S3I, BMI-S4P and BMI-S3I). The FT-IR analysis revealed that the maleimide and thiol groups of all the cured resins were almost consumed by the thermal thiol-Michael reaction. Although the temperature at which the thiol-maleimide reaction starts to occur was reduced by the addition of Me2PPh, the flexural strength, modulus and thermal degradation temperature for the cured resins with Me2PPh were rather lower than those for the cured resins without Me2PPh. Regarding the cured resins without Me2PPh, BMI-SPPSO/S4P 2/1 and BMI-SPPSO/S3I 2/3 exhibited the highest flexural strength and modulus among BMI-SPPSO/S4Ps and BMI-SPPSO/S3Is, respectively. The glass transition temperature (T-g) and 5% weight loss temperature (T-d5) for the cured resins increased with increasing SPPSO/S4P or SPPSO/S3I ratio, and BMI-SPPSO exhibited the highest T-g (170 degrees C) and T-d5 (442 degrees C).