Study of physical properties associated with some binary mixtures of chiral ferroelectric liquid crystalline compounds
Barnali Barman*, Malay Kumar Das
Department of Physics, University of North Bengal, 734 013, Siliguri, West Bengal, India
*E-mail ID: barnalibarman1991@gmail.com
Abstract
Among the various advanced technological materials in the modern era; Liquid Crystals (LCs) has become one of the most important self-organizing molecular materials with their growing applications in the various field of science. The research associated with the Ferroelectric Liquid Crystals (FLCs) has become a subject of most intense area during the past few decades owing to their valuable intrinsic fundamental properties.At present their successful utilization in flat television screens, fast electro-optical switching devices etc. makes them extremely demandable in the commercial field. The fulfilment of this promise depends greatly on an improved understanding on the physical properties of the FLC materials. However no single materials can exhibit all the desired properties for different applications. In order to fulfil all the requirements of the device manufacturer; preparation of suitable binary mixtures is one of the most simple and elegant way in the field of LC Research. Keeping this in mind some mixtures have prepared by using pure chiral FLC compounds [1,2,3] and investigated in the light of the static dielectric permittivity (ε), dielectric anisotropy (∆ε), spontaneous polarization (Ps), response time (τ), torsional bulk viscosity (h) and dielectric spectroscopy. The temperature variation of Ps of the studied mixtures provides a preliminary idea about the order of the associated phase transitions namely SmA*-SmC* and N*-SmC*. The activation energy of all the mixtures have been determined from the best fitted Arrhenius plot. This assignment mainly contributes to the preparation and investigation of some smart multifunctional FLC mixtures aimed for optoelectronic and photonic applications.
References
[1]A.Bubnov,M.Kaspar,V.Novotna,V.Hamplova,M.Glogarova,N.Kapernaum,F.Giesselmann; Liq. Cryst.2008, 35, 1329-1337.doi.org/10.1080/02678290802585525.
[2]B.Barman, B.Das, M.K.Das, V. Hamplová, A.Bubnov, Journal of Molecular Liquids.2019, 283.472-781. doi.org/10.1016/j.molliq.2019.03.071.
[3]M.K.Das,B.Barman,B.Das,V.Hamplová,A.Bubnov,Crystals.2019,9,473;doi:10.3390/cryst9090473.
One can observe some contribution for high frequency part of the dielectric spectrum, due to non−zero resistivity of electrode material or non−zero inductivity of connecting wires. At a higher frequency regime (~ few MHz) some relaxation process was found which is attributed due to the finite resistivity of (Indium Tin Oxide) ITO layers present in measuring cells (in which liquid crystals are filled) that is why so named. For more information about ITO effect one can read the following references.
There is no indication of such behaviour which arises due to the complex interaction of the two components of the binary mixtures in our observation.
[1] Perkowski, P. Dielectric spectroscopy of liquid crystals, Theoritical model of ITO electrodes influence on dielectric measurements. Opto-Electronics Review.2009, 17 (2), 180-186.doi.org/10.2478/s11772-008-0062-8.
[2] Shukla, R.K.; Raina, K. K.; Hamplová,V.; Kašpar,M.; Bubnov, A. Dielectric behaviour of the composite system: multiwall carbon nanotubes dispersed in ferroelectric liquid crystal, Phase Transitions.2011, 84(9-10), 850-857.doi.org/10.1080/01411594.2011.558300.
[3] Das, M.K.; Barman, B.; Das,B.; Hamplová, V.; Bubnov, A. Dielectric Properties of Chiral Ferroelectric Liquid Crystalline Compounds with Three Aromatic Rings Connected by Ester Groups. Crystals 2019 ,9, 473.
[4] Perkowski, P. Dielectric spectroscopy of liquid crystals. Electrodes resistivity and connecting wires inductance influence on dielectric measurements. Opto Electronics Review 20(1), 79–86 DOI: 10.2478/s11772−012−0004−3.
[5] Sathyanarayana , P.; Radhika, S.; Sadashiva , B. K. and Dhara, S; Structure–property correlation of a hockey stick-shaped compound exhibiting N-SmA-SmCa phase transitions, Soft Matter, 2012, 8, 2322, DOI: 10.1039/c2sm06767f.
