| Abstract: | Several aromatic mono- and dicyanate monomers bearing ether and ketone groups in the main chain have been synthesized through high-yield reactions widely used in organic chemistry. FT-IR and NMR were used to characterize these monomers and the intermediate products. The cyclotrimerization reaction was studied by DSC in monocyanate models, and the enthalpy of the reaction was determined. The value obtained was approximately 95 kJ/mol of cyanate irrespective of the substituent and symmetry of the substitution. For short dicyanates, cyclotrimerization did not reach completion, and for long dicyanates, the enthalpy of reaction could not be evaluated with accuracy. The resulting cured polycyanurates networks, due to the selectivity of the cyclotrimerization reaction, could be considered as true fully aromatic crosslinked poly(ether ketone)s with controlled structure. Tg values of the networks were above 180°C. The higher values were found for shorter dicyanates and for monomers with para substitution. The 1% and 5% weight loss values in nitrogen were above 310 and 380°C, respectively, with char yields in the range 50–60%. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3155–3168, 1999 |
