Mechanisms and kinetics of isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane with 5,5-dimethylbarbituric acid in the presence of triphenylphosphine

Mechanisms and kinetics of isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) with 5,5-dimethylbarbituric acid (55BTA) in the presence of triphenylphosphine (Ph3P, as a base catalyst for aza-Michael addition reaction) were investigated. Both model-free and model-fitting methods were used to determine triplet kinetic parameters, and comparable kinetic parameters obtained. Based on the model-free method, average activation energy (Eα) and pre-exponential factor (Aα) are 33 ± 1 kJ mol−1 and 8267 ± 2 min−1 in the α range 0.1-0.9, respectively, with g(α) = [(1 − α)−0.1 − 1]/0.1 [i.e. f(α) = (1 − α)1.1]. As to the model-free method, overall activation energy (E) and pre-exponential (A) are 32 ± 1 kJ mol−1 and 4583 ± 1 min−1 with the g(α) = [(1 − α)−0.1 − 1]/0.1. Aza-Michael addition reaction mechanism played an important role in the polymerization of BMI/55BTA in the presence of Ph3P at low temperature. By contrast, free radical polymerization predominated in the BMI/55BTA system at higher temperature.