Liquid crystalline thermosets from triaromatic azomethine group containing diepoxides and 4,4´-methylenedianiline

Abstract

Five triaromatic azomethine-linked diepoxides have been cured by reaction with 4,4′-methyl-enedianiline (MDA) in a molar ratio epoxide/amine of 1:1 and 2:1. The influence of the structure of monomers, of the molar ratio epoxide/amine, and of the curing conditions on the formation of liquid crystalline networks was studied. Initially a decrease of the clearing temperature was caused by mixing with the nonmesogenic diamine. The clearing point of the mixture increased with conversion, and thermosets with a liquid crystal order of the monomers were obtained from the 2:1 combinations. Curing occurs in two stages as revealed by DSC: first epoxy/amine reaction occurs, and at higher temperature homopolymerisation of residual oxirane takes place. This is due to non-homogeneous melting of the diepoxides in dynamic curing.