The Diels-Alder polymerization reaction between a bisdiene derived from abi
etic acid and 4,4'-diphenylmethanedimaleimide (bismaleimide) was studied. T
he bisdiene was the dehydrodecarboxylation product of abietic acid, denoted
here as diabietyl ketone. An insoluble and infusible polymer with high mol
ecular weight was obtained. It is a poly(ketoimide) with hydrophenanthrene
moieties in the backbone. The analyses showed that the chemical structure o
f the polymer was different from that expected. The polymer structural unit
was found to contain bismaleimide and diabietyl ketone units not in a mola
r ratio of 1:1, as expected, but in a ratio of 5-6:1. The phenomenon was as
cribed to the difference between the rates of the two concomitant reactions
in the synthesis; the homopolymerization of bismaleimide and the proper Di
els-Alder polymerization. The polymer having in structure the monomer units
in 1:1 ratio was, however, obtained by both the dehydrodecarboxylation of
the diacid resulted from the Diels-Alder reaction between abietic acid and
4,4'-diphenylmethanedimaleimide and the polycondensation of the ketone of m
aleated abietic acid with 4,4'-diaminodiphenylmethane. The monomers and the
polymers were investigated by usual physical and chemical methods. The the
rmal stability of polymers was evaluated by TGA. The synthesized polymers w
ere identical heat-resistant as the crosslinked polymer obtained from 4,4'-
diphenylmethanedimaleimide. They were stable in air up to 360 degrees C.