Spectroscopic and DFT investigation of a ferroelectric nematic liquid crystal

Understanding the molecular dynamics of ferroelectric nematic and its thermodynamical behaviour is crucial for the development of advanced technologies because of their unique electro-optical properties. In this paper, a detailed study of temperature dependent Raman spectroscopy of a ferroelectric nematic liquid crystal, namely (4-((4-nitrophenoxy)carbonyl) phenyl-2,4-dimethoxybenzoate) or RM734 is carried out. Raman spectral features of the sample, viz., peak position, linewidth and peak intensity have been investigated for temperature range of 30–194°C. The integrated peak intensity combined with full width at half maximum of different vibrational peak associated with different chemical bonds are carefully analysed at various temperatures to understand the ferroelectric behaviour and polar ordering of the molecules in the LC state. Also, IR studies have been carried out to obtain a complete detailed information of the structure and the vibrational characteristics of the sample. UV spectroscopy study of the sample has also been done to determine the key electronic transition properties such as absorption co-efficient and band gap of the compound at room temperature. Further, the Density Functional theory (DFT) is used for geometry optimisation and assignments of vibrational bands and are compared with the experimental results.