Study of phase transitions in a bent-core liquid crystal probed by infrared spectroscopy

A new four ring bent-core liquid crystal (4′-n-octylphenylazo)-phenyl-4-yl-3-[N-(4′-n-dodecyloxy-2-hydroxybenzylidene) amino]-2-methyl benzoate has been synthesized and investigated using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and temperature-dependent Fourier transform infrared (TD-FTIR) spectroscopy. DSC and POM were used to detect transition temperatures and identify mesophases. TD-FTIR spectroscopic technique was utilized as a probe to analyze the dynamics of the liquid crystal molecules during the phase transition. The quantum chemical density functional theory (DFT) was used to predict the most stable conformation and the correct vibrational assignment of different modes. Combined theoretical and experimental techniques provided a clear picture of the structural modifications and dynamics of mesophases during the phase transitions.