DFT-based numerical study of the re-entrant phase and optical parameters of the homologous series of MBC liquid crystal molecules studied under the influence of an electric field

The homologous series of MBC liquid crystals (LCs) show re-entrant nematic phase (chiral nature or adverse order) under the external electric field in the THz frequency range. The MBC LCs show the phase conversion from isotropic to nematic and subsequently, nematic to isotropic with the variation in electric field and length of alkyl chain in the molecular structure. The negative order parameter is decreased and the positive order parameter of the MBC series is decreased with the length of the alkyl chain of the molecular structure. The positive values of the birefringence of MBC series are reduced; however, adverse birefringence approximately remains constant. On account of the director angle, a short alkyl chain has smaller values, but after 5 MBC, all the molecules are parallel to the applied electric field and maintain a large perspective θ = 90. The refractive index of MBC increases with the extension of the alkyl chain length in the structure. The abstract image of the MBC LC series indicates the phase variation of the MBC series and the band gap of the nematic phase MBC is also affected by the applied electric field. (author)