Enhanced liquid crystal properties in symmetric ethers containing the oxazepine core: synthesis and characterization of seven member heterocyclic dimers

Abstract

Four new series of symmetric dimers derived from the basic heterocyclic oxazepine core were designed, synthesized, characterized and investigated for liquid crystal properties. The chemical structures of the prepared molecules were characterized by infrared, 1H/13C nuclear magnetic resonance spectra and elemental analysis. Thermal properties and mesophase textures were evaluated by using a combination of differential scanning calorimetry and polarized optical microscopy techniques. Most of the compounds exhibited monotropic liquid crystalline phases in cooling processes. The effect of the spacer chain length and terminal alkoxy chain were studied for the influence on the type of mesophase formed by the homologous series of compounds. Lower members possessing the methylene spacer and a terminal alkoxy-chain favoured smectogenic properties; those derived from medium methylene spacer with terminal alkoxy chain favoured nematogenic properties whereas molecules derived with a higher methylene spacer with terminal alkoxy chain members did not favour any liquid crystalline properties.