CURING REACTIONS OF BISMALEIMIDE RESINS CATALYZED BY TRIPHENYLPHOSPHINE - HIGH-RESOLUTION SOLID-STATE C-13 NMR-STUDY

The curing reactions of bismaleimide resins consisted of N,N'-4,4'-dip henylmethanebismaleimide (BMI) and o,o'-diallylbisphenol-A (DABA) in t he presence of triphenylphosphine (TPP) as a catalyst were investigate d, DSC measurements showed that the catalytic effect of TPP on the cur ing reaction of BMI was more in the presence of DABA than in its absen ce. In order to explore this curing reaction, N-phenylmaleimide (PMI) and o-allylphenol (AP) were selected as model compounds. The products of the PMI/TPP system were oligomers and polymers of PMI, whereas the main product of the PMI/AP/TPP system was the PMI trimer which had the five-membered ring formed via the phosphonium ylide intermediate. In these model reactions, C-13 NMR was found to be useful to distinguish between trimerization and polymerization of PMI. On the basis of the r esults of the model reactions. the curing reactions of bismaleimide re sins were investigated by high resolution solid state C-13 NMR techniq ues. In the BMI/TPP system, maleimides polymerize above 175 degrees C, but the polymerization does not proceed at 120 degrees C. On the othe r hand, maleimides trimerize above 120 degrees C in the presence of DA BA and TPP. The mechanism of the trimerization is briefly discussed.