Design of hydrogen bond liquid crystals towards various electronic applications

• Published in: Journal of molecular liquids Vol. 408; p. 125189
• Main Authors: Janaki, Vidya. P., Moorthi, S., Madhu Mohan, M.L.N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-08-2024
• Subjects: Dielectric relaxation; Liquid crystal; Memory effect; Nematic; Thermistor; Thermistor; Liquid crystal; Memory effect; Nematic; Dielectric relaxation
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2024.125189

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•Optical, thermal and electrical characterization of thermotropic LC is reported.•A new technique for phase transition temperature identification is discussed.•For the first time in the history of liquid crystals, dielectrical hysteresis is reported.•Equivalent circuit modeling and simulated using LTspice is reported.•The experimental results are in good concurrence with simulated data.
A homologous series of hydrogen bond liquid crystals has been synthesized by mixing 4 − butyl benzoic acid (4BA) and p-n-alkyloxybenzoic acids (nBAO). Four homologues are isolated by varying the carbon number of alkyloxy benzoic acid from nonyloxy to dodecycloxy and the obtained mesogens are abbreviated as 4BA + 9BAO, 4BA + 10BAO, 4BA + 11BAO and 4BA + 12BAO. Presence of hydrogen bond is evinced through Fourier transform infrared spectroscopic studies. Optical microscopic studies ensure that all the four mesogens are mono-phase variant and exhibit nematic phase. Another interesting feature observed is the presence of Parachromatism in entire thermal span of nematic phase in all the four mesogens. The phase changeover temperatures and enthalpy values are elucidated from DSC studies. The thermal stability and thermal span of the phases has been inferred from phase diagram. Dielectric studies have been done in the nematic phase of all the mesogens and the activation energies has been calculated. Electrical analysis includes the measurement of resistance, permittivity and dielectric loss with respect to the applied stimulus. A new method to identify transition temperature is revealed. Yet another interesting observation is that the presence of memory and characteristics of thermistor in the nematic phase are discussed in detail. Furthermore, an equivalent circuit modelling of mesogen has been done and with a study on its behaviour has been studied using LTspice.