Thermal and Optical Characterization of Multiple Hydrogen Bonded Liquid Crystals and Its Application in Display Devices

Novel homologous series of phloroglucinol (PG) and 4-n-alkyloxybenzoic acid (nOBA, n = 4 to 12) hydrogen bonded liquid crystal (HBLC) complex have been designed and synthesized. In the self-assembly process, intermolecular interaction between the molecules produce the multiple HBLCs with various shapes and structure. Existences of multiple hydrogen bonds in the PG+nOBA HBLC complex are confirmed by FT-IR spectroscopic method. Textural changes along with that phase transition temperature are identified by polarizing optical microscope (POM). Due to the polymerization, an induced stabilized smectic phase along with re-entrant disordered phase is noticed in the present PG+nOBA HBLC complex. The thermodynamic properties such as enthalpy values, thermal stability and thermal span width are analyzed by differential scanning calorimetry (DSC). An induced re-entrant phenomenon in the present HBLC complex is due to the dipolar aggregation has been discussed. The band gap energy is calculated by UV–Visible spectrometer (UV–Vis) which gives the clear evidence for the existence of band gap energy value (Eg = 3.5 eV) in the present HBLC complex. The desirable band gap in the present HBLC and its display device application is reported in the present communication. The other liquid crystal parameters (thermal stability, tilt angle, etc.) are also discussed.