The synthesis, characterization and investigation of electro-optic properties of polar group substituted banana shaped mesogens

Liquid crystals are an intermediate state of matter between isotropic liquids and crystals. Although the most common use of these materials in the field of display technology; they are advanced organic materials which are included in many different applications such as smart glasses, energy-efficient liquid crystal-added batteries, biosensors and controlled drug release. Banana-shaped liquid crystals, a noteworthy subclass of thermotropic liquid crystals, have been the focus of interest for the emergence of polar order and chiral superstructures in mesophases, despite the achiral nature of the molecule. Banana-shaped liquid crystals exhibit a wide variety of liquid crystal phases. One of the most important features affecting these phases is the lateral group substitution. Usually, the lateral group substitution takes place on the central core and the use of polar lateral groups mainly affects the occurrence of mesophase. For example, cyano substitution in the 4-position of resorcinol ring induces to form polar smectic phases as well as blue phases depending on the structure of the rod-like wing groups and nature of attached terminal groups, whereas other substitutions results in by the loss of LC phases. In this study, new bent-core liquid crystalline materials consisting of a 4-cyanoresorcinol central unit with two terephthalate based rod-like wings and terminated by (S)-3,7-dimethyloctyloxy chiral group and n-alkoxy chain were synthesized. The new compounds were characterized by spectroscopic methods (1H-NMR and 13C-NMR) and elemental analysis. The mesomorphic properties were investigated by polarizing microscopy, differential scanning calorimetry and electro-optic methods to study the influence of molecular chirality on the superstructural chirality and polar order in lamellar liquid crystalline phases.