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

The kinetics and mechanisms of polymerization of equifunctional 4,4'-(N,N'- bismaleimide)-diphenylmethane/2,2'-diallyl-bisphenol A (BMDM/DABPA) and mod el (phenylmaleimide/2-allylphenol) (PMI/AP) systems have been studied in th e temperature range 140 - 400 degreesC using IR-, H-1 and C-13 NMR spectros copy, GC/MS, DSC, and isothermal calorimetry. It was established that the c ure mechanism consisted of a unique combination of step-wise and chain poly merization as well as polycondensation reactions: the polyaddition "ene" ad dition of the allyl group to the maleimide and the consecutive and parallel chain polymerization of maleimide and propenyl groups generated by the fir st reaction. The last reaction was the main branching reaction. The second source of branching was the dehydration reaction of phenol groups (polycond ensation reaction) that proceeds with the participation of the 1:1 "ene" ad duct as one of the component. Homopolymerization of maleimide groups procee ded autocatalytically, initiated by free radicals generated by thermal deco mposition of the maleimide-propenyl group's donor-acceptor pairs. The steri c hindrance in 2,2'-diallyl-bisphenol A prevented the reversible Diels-Alde r reaction, but the reaction proceeded in model systems. Some thermodynamic and kinetics parameters of the reactions have been determined.