Dielectric and Spontaneous Polarization Studies of a Ferroelectric Chiral Smectic Liquid Crystal

Abraham K. George, C. Carboni, S. H. Al-Harthi, W. M. Zoghaib, D. M. Potukuchi

Department of Chemistry, Sultan Qaboos University, Muscat, Oman.
Department of Physics, Sultan Qaboos University, Muscat, Oman.
Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University, Kakinada, India.

DOI: 10.4236/wjcmp.2012.22013                

Abstract

Dielectric relaxation and spontaneous polarization studies have been carried out in a low molar mass organosiloxane liquid crystal, TSi10PPBN4 which displays a wide temperature range of de Vries Smectic A* and chiral Smectic C* phases. The temperature variation of the permittivity and dielectric loss studied are found to have anomalous variations in the vicinity of the phase transitions. The frequency variation of permittivity and dielectric loss are also studied in the de Vries Smectic A* and Smectic C* phases. The relaxation frequency, f_R is found to decrease with decreasing temperature. Temperature variation of fR is found to follow an Arrhenius shift from which the activation energy is estimated. The thermal variation of the spontaneous polarization, Ps is measured using the polarization reversal technique in the Smectic C* phase. Ps increases initially, reaches a peak value and then drops drastically in the vicinity of the SmC*-SmA*de Vries phase transition.

Keywords

Smectic C* and Smectic A*de Vries Phases; Dielectric Permittivity; Dielectric Relaxation; Activation Energy; Spontaneous Polarization

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	G. R. Luckhurst and C. A. Veracini, “The Molecular Dynamics of Liquid Crystals,” Kluwer Academic Publishers, Dordrecht, 1994.
[2]	J. Naciri, J. Ruth, G. Crawford, R. Shashidar and B. R. Ratna, “Novel Ferroelectric and Electroclinic Organosi-loxane Liquid Crystals,” Chemistry Materials, Vol. 7, No. 7, 1995, pp. 1397-1402. doi:10.1021/cm00055a019
[3]	W. K. Robinson, P. S. Kloess, S. P. Perkins, C. Carboni and H. J. Coles, “Ferroelectric and Antiferroelectric Low Molar Mass Organosiloxane Liquid Crystals,” Liquid Crystals, Vol. 25, No. 3, 1998, pp. 301-307. doi:10.1080/026782998206092
[4]	W. K. Robinson, P. Lehman and H. J. Coles, “Bi-Mesogenic Fluorinated Organosiloxanes: An Electro-Optic Study Revealing Unusual Phase Behavior,” Molecular Crystals and Liquid Crystals, Vol. 328, No. 1, 1999, pp. 229-236. doi:10.1080/10587259908026063
[5]	A. Kaeding and P. Zugenmaier, “Investigations of a Homologous Series of Chiral Siloxane Based Dimesogenic Compounds,” Liquid Crystals, Vol. 25, No. 4, 1998, pp. 449-457. doi:10.1080/026782998205958
[6]	K. Miyasato, S. Abe, H. Takezoe, A. Fukuda and E. Kuze, “Direct Method with Triangular Waves for Measuring Spontaneous Polarization in Ferroelectric Liquid Crystals,” Japanese Journal of Applied Physics, Vol. 22, 1983, pp. L661-L663. doi:10.1143/JJAP.22.L661
[7]	J. V. Selinger, P. J. Collins and R. Shashidar, “Field Dependent Tilt and Birefringence of Electroclinic Liquid Crystals,” Physics Review E, Vol. 64, No. 6, 2001, pp. 1-9.
[8]	J. Naciri, C. Carboni and A. K. George, “Low Transition Temperature Organosiloxane Liquid Crystals Displaying a de Vries Smectic A Phase,” Liquid Crystals, Vol. 30, No. 2, 2003, pp. 219-225. doi:10.1080/0267829021000060250
[9]	D. M. Potukuchi, A. K. George, C. Carboni, S. H. Al-Harthi and J. Naciri, “Low Frequency Dielectric Relaxation, Spontaneous Polarization, Optical Tilt Angle and Response Time Investigation in a Fluo-rinated Ferroelectric Liquid Crystal,” Ferroelectrics, Vol. 300, No. 1, 2004, pp. 79-93. doi:10.1080/00150190490442245
[10]	A. K. George, M. Al-Hinai, D. M. Potukuchi, S. H. Al-Harthi and C. Carboni, “Study of Dipole Dynamics and Pre-transitional Effects at Isotropic to Nematic Phase Transition by Low-Frequency Dielectric Relaxation Measurements,” Phase Transitions, Vol. 76, No. 12, 2003, pp. 1037-1045. doi:10.1080/0141159031000114865
[11]	M. Wojciechowski, L. A. Gromice and G. W. Bαk, “Dielectric Relaxations in Liquid Crystalline 4-(1-Methylhept-locabonyl)phenyl-4’-(ω-perfluoroacetoxypropoxy)biphenyl-4-carboxylate,” Journal of Molecular Liquids, Vol. 86, No. 1-3, 2000, pp. 269-272. doi:10.1016/S0167-7322(99)00148-8
[12]	B. Zeks and R. Blinc, “Dielectric Properties of Smectic C* Liquid Crystals,” Molecular Crystals and Liquid Crystals, Vol. 220, No. 1, 1992, pp. 63-65. doi:10.1080/10587259208033429
[13]	P. G. Castello, Y. P. Kalmykov and J. K. Vij, “High Frequency Dielectric Behavior of a Ferroelectric Liquid Crystal near the Smectic C*-Smectic A Phase Transition,” Physical Review A, Vol. 46, No. 8, 1992, pp. 4852-4858.
[14]	A. K. George, M. Al-Hinai, D. M. Potukuchi, C. Carboni, S. H. Al-Harthi and J. Naciri, “Dielectric Response in the Smectic A and Smectic C* Phases of a Ferroelectric Liquid Crystal, 12CN5(R*),” Molecular Crystals and Liquid Crystals, Vol. 409, No. 1, 2004, pp. 343-353. doi:10.1080/15421400490431714
[15]	A. de Vries, “Experimental Evidence Concerning Two Different Kinds of Smectic C to Smectic A Transitions,” Molecular Crystals and Liquid Crystals, Vol. 41, No. 2, 1977, pp. 27-31. doi:10.1080/01406567708071949
[16]	C. Carboni, R. Mehdi, A. K. George and S. H. Al-Harthi, “Electroclinic Effect in Low Molar Mass Organosiloxane Liquid Crystal,” Molecular Crys-tals and Liquid Crystals, Vol. 410, No. 1, 2004, pp. 61-69. doi:10.1080/15421400490434937