Synthesis and properties of isothiocyanate liquid crystals containing cyclohexene unit

Abstract

ABSTRACT Isothiocyanate liquid crystals containing cyclohexene core unit were designed and synthesised through a practical synthetic route. The structures of the designed mesogens and intermediate products were confirmed by 1H NMR, 13C NMR and GC/EI-MS. The effect of this core unit on the mesomorphic and physical properties were investigated by comparing with four reference compounds based on trans-cyclohexane and phenyl. The results illustrated that the function of this unit on the melting points and nematic phase range fell in between classical cores trans-cyclohexane and benzene. When compared with phenyl, this core structure can depress the presence of smectic phase. The birefringence and dielectric anisotropy values of the cyclohexene-based liquid crystals were higher than the trans-cyclohexane-based references, respectively, illustrating that this core could be used as an enhanced version of trans-cyclohexane. Density Functional Theory (DFT) calculations of energy minimum structures, polarisability anisotropy (Δα) and dipole moment (µ) were carried out at last to clarify the structure–property relationship of the mesogens.