RIGID-ROD THERMOSETS BASED ON 1,3,5-TRIAZINE-LINKED AROMATIC ESTER SEGMENTS

Liquid-crystalline (LC) thermosets were prepared by the thermal cyclotrimerization of dicyanate compounds of ring-substituted bis(4-hydroxyphenyl) terephthalates. The resulting triazine networks formed a mesophase as the curing reaction proceeded, thereby enabling alignment in applied fields. Alignment of the LC phase during the curing process under the influence of a magnetic field produced oriented triazine networks with a smecticlike molecular organization. The effect of this anisotropy on the properties of these networks was investigated by both wide-angle X-ray diffraction and by measuring the coefficient of thermal expansion parallel and perpendicular to the direction of alignment. Remarkably well-oriented triazine networks were obtained (f approximately 0.50) with low values of the coefficient of thermal expansion observed (17 ppm/degrees-C) in the direction of the applied field. The triazine networks have glass transition temperatures of approximately 190-degrees-C and show little decomposition until approximately 440-degrees-C. The alignment of the LC triazine networks induced by curing in magnetic fields was found to be thermally stable until at least 100-degrees-C above the glass transition temperature.