Effect of intramolecular cycles on the formation of rigid polycyanate networks

Abstract

On the basis of the recursive method of Macosko and Miller (Macromolecules, 1976, 9, 199), a theoretical scheme with due considerations on the formation of intramolecular cycles is developed for polycyanate networks. Experimental observations on gelation behaviour of a typical aromatic dicyanate, 2,2-bis(4-cyanatophenyl)propane, are compared with the theoretical predictions. Results indicate that deviations from the classical behaviour (including the sluggish molecular weight build-up during the pre-gelation regime, the delayed gelation, and the steeper increase of gel fraction in the post-gelation stage) can be explained in terms of effects of intramolecular cyclisation, which is negligible in the early stage of curing, becomes more important with increasing conversion, and is then counterbalanced (presumably by loop-interlocking) in the post gelation regime.