The polyaddition, chain, and polycondensation machanisms of formation of networks based on bismaleimides

Abstract

The kinetics and mechanisms of polymerization of equifunctional 4,4'-(N,N'-bismaleimide)-diphenylmethane/2,2'-diallyl-bisphenol A (BMDM/DABPA) and model (phenylmaleimide/2-allylphenol) (PMI/AP) systems have been studied in the temperature range 140 – 400 °C using IR-, 1H and 13C NMR spectroscopy, GC/MS, DSC, and isothermal calorimetry. It was established that the cure mechanism consisted of a unique combination of step-wise and chain polymerization of maleimide and propenyl groups generated by the first reaction. The last reaction was the main branching reaction. The second source of branching was the dehydration reaction of phenol groups (polycondensation reaction) that proceeds with the participation of the 1:1 “ene” adduct as one of the component. Homopolymerization of maleimide groups proceeded autocatalytically, initiated by free radicals generated by thermal decomposition of the maleimide-propenyl group's donor–acceptor pairs. The steric hindrance in 2,2'-diallyl-bisphenol A prevented the reversible Diels–Alder reaction, but the reaction proceeded in model systems. Some thermodynamic and kinetics parameters of the reactions have been determined.