Phase transformations of a liquid crystalline epoxy during curing

Abstract

The phase transformations of a novel liquid crystalline epoxy, diglycidyl ether of 4,4'-dihydroxy-[alpha]-methylstilbene (DGEDHMS), from isotropic phase to liquid crystalline phase during curing have been studied using a cross-polarized optical microscope equipped with a hot-stage. Time-temperature-transformation (TTT) diagrams were constructed following the isothermal curing of the DGEDHMS in the isotropic phase with a difunctional amine, the aniline adduct of the DGEDHMS, and a tetrafunctional sulfonamido amine, sulfanilamide. Our results show that curing with the difunctional amine results in a nematic-like texture, while curing with the tetrafunctional sulfonamido amine leads to a smectic-like texture. Furthermore, curing with the difunctional amine gives rise to a faster development of the liquid crystalline phase, but with a less stable mesophase as compared to the tetrafunctional curing agent. These results are explained in terms of intermolecular interaction and the chain conformation anisotropy resulting from the curing reactions. The TTT diagram will be useful for providing guidelines for processing these new liquid crystalline epoxy systems.