Conjugated polymer liquid crystal solutions: control of conformation and alignment

Stable solutions of conjugated poly(phenylene vinylene)s and poly(phenylene ethynylene)s in nematic liquid crystals are reported. The polymers all contain triptycene units fused into their backbones to obtain the high solubility needed to maintain solubility in complex liquid crystalline media. The polymer backbones align with the director of the nematic liquid crystal, and by applying electric fields the polymers can be reoriented. The polymers all displayed lower band gaps in the liquid crystal solvents relative to those obtained in standard solvents such as methylene chloride. Hence, the liquid crystal solution induces a chain-extended highly conjugated structure in the polymers, which is generally associated with optimization of the polymer properties.