Elaboration of Side-Chain Liquid-Crystalline Elastomers and Study of Their Swelling Behavior in Anisotropic Solvents

A poly [6-(4'-cyanophenyl-4"-phenoxy) alkyl acrylate] side chain liquid crystalline elastomer and a poly [n-butylacrylate] network were synthesized via photopolymerization using 1,6-hexanediol diacrylate as a crosslinking agent. The materials obtained were characterized by differential scanning calorimetry and polarized optical microscopy. In particular, the latter method allowed to follow the swelling behavior of the polymer networks in a low molar weight liquid crystal (LC) and to observe the formation of LC gels. In the case of the anisotropic network, a stable nematic gel phase and a miscibility gap were observed, in relationship with the nematic-isotropic transition temperatures of both LC-solvent and LC-gel. The experimental phase diagrams were well reproduced by a mean field model combining the Flory-Rehner model for isotropic mixing and the Maier Saupe theory for nematic ordering.