Experimental and computational simulations of nematogenic liquid crystals based on cinnamic acid in pure and mixed state

Abstract

ABSTRACT Homologous series of nematogenic azomethine liquid crystals bearing different terminal alkoxy-chain lengths, 4-(cinnamolyloxy)benzylidene-4ʹ-n-alkoxyanilines (In), were synthesised and investigated via practical and theoretical tools. Differential scanning calorimetry (DSC) and polarised optical microscopy (POM) were used for mesomorphic and optical investigations. While the computational simulations and geometrical parameter estimations were carried out using a DFT approach at B3LYP/6-31 G(d,p) level of theory. The results revealed that all of the investigated compounds showed to exhibit the enantiotropic nematic mesophase. The temperature range of the nematic phase depends on the length of the terminally attached flexible alkoxy chain. Theoretical calculations were conducted and found to confirm the experimental data values of the mesophase stability and its temperature range. Furthermore, the length of the terminal alkoxy chains showed to exhibit remarkable effects on the stability of the mesophase as well as their thermal and physical properties. The mesomorphic and optical properties determined were correlated with the theoretically calculated parameters and the study revealed that many factors in different extents contribute together to manifest the behaviour of the observed nematic phase. The binary phase diagram of two corresponding homologues was constructed and their binary phase thermal properties were discussed in terms of the temperature range of the nematic phase.