Synthesis, characterization and photoreaction of side‐chain liquid‐crystalline polymers and copolymers comprising alkenyloxy‐biphenyl mesogen

Abstract Photoreactive (meth)acrylate monomers having mesogenic groups based on 4‐hexyloxy‐4′‐(3‐methyl‐2‐butenyloxy)biphenyl and 4‐hexyloxy‐4′‐(2‐butenyloxy)biphenyl were synthesized. Methacrylate monomers (3c, d) and acrylate monomer having 3‐methyl‐2‐butenyloxy group (3b) were polymerized by free radical mechanism; the acrylate monomer having 2‐butenyloxy group (3a) caused gelation during the polymerization. To obtain photoreactivity, 4‐benzoylphenyl (meth)acrylates were radically copolymerized with monomers 3b and 3d. Thermal behavior of (co)polymers was determined by differential scanning calorimetry, polarized optical microscopy and temperature‐controlled X‐ray analysis. (Co)polymers showed liquid‐crystalline behaviour with nematic and smectic phases. UV‐irradiation was used to photochemically crosslink copolymer films, and the resultant films were insoluble in organic solvents. The uniaxially oriented copolymer thin film was photo‐crosslinked and showed thermally stable orientation.