Moisture Permeation in Liquid Crystalline Epoxy Thermosets

Abstract

Abstract A liquid crystalline thermoset (LCT), 4,4′‐diglycidyloxy‐α‐methylstilbene/sulfanilamide, is studied by dynamic mechanical and vapor sorption measurements. Sub‐ T g transitions are assigned to the specific segmental motions through molecular modeling and used to define the environmental temperatures for the study of water transport properties in LCT. The variation of moisture transport with amine‐epoxy ratio reveals that the crosslink density and local concentration of polar groups play the key role in determining both the diffusivity and solubility. The LCT exhibits much lower water diffusion than analogous isotropic networks while the solubility is essentially the same. Segmental flexibility and an ordered smectic layered structure are responsible for the lower permeability.