Liquid crystalline elastomers based on diglycidyl terminated monomers and aliphatic acids. Part 1: synthesis and characterization

Liquid crystalline elastomers (LCEs) were prepared by reacting rigid-rod mesogenic epoxy monomers with aliphatic diacids of variable length. The influence of acid and nature of epoxy monomer on the mechanism of network growth was investigated through DSC, FT-IR, MALDI, 1H and 13C NMR and rheological experiments. Depending on the nature of epoxy monomer, different mechanisms of network growth occurred, which were responsible for the formation of elastomers with different extent of branching. Isotropization temperatures, entalpies and entropies, and the nature of mesophases were also analyzed through DSC and X-ray diffraction, carried out on unstrained elastomers. It was found that both the rigid-rod mesogens and the aliphatic portions of carboxylic acids contribute to stabilize the mesophase. Moreover, upon stretching, all the LCEs exhibited the polydomain-to-monodomain transition, which is typical of this class of materials