Synthesis and properties of siloxane modified perylene bisimide discotic liquid crystals

A series of symmetric and asymmetric 1,6,7,12-tetrachloroperylene bisimides (PBICls) were synthesized and modified by siloxane substituents at the imide nitrogen atom. Siloxane substitutions do not apparently affect the electronic properties of PBICIs as demonstrated by CV experiments. They display both thermotropic and lyotropic liquid crystalline behaviors. The effect of different siloxane substituents on their liquid crystal structures was investigated in detail. Small angle X-ray scattering indicates that PBICls adopt hexagonal columnar packing in thermotropic liquid crystals. In addition, PBICls exhibit good optical properties, good solubility and film-forming ability. Thus the oriented films of PBICl liquid crystals could be easily fabricated by mechanical shear, which show anisotropic properties in UV-vis absorption spectra.