Characteristics of electrical properties of wide temperature range TGB phases in liquid crystal dimers

• Autorzy: Dhar R. , Pandey M. B. , Pandey V. S. , Pandey A. S. , Das I. M. L. , Achalkumar A. S. , Yelamaggad C. V.
• Języki publikacji: EN

Abstrakty

EN

4-n-decyloxy-4'-(cholesteryloxycarbonyl-1-butyloxy) chalcone and its two successive homologous are optically active dimeric compound derived from cholesterol. They possess wide temperature ranges of two twist grain boundary (TGB) phases namely TGBA and TGBC*. Comprehensive dielectric studies have been carried out for these compounds in the frequency range of 1 Hz to 10 MHz for different conditions of molecular anchoring. Various electrical parameter viz. dielectric permittivity, dielectric anisotropy, dc conductivity, and activation energy have been determined for these two TGB phases. Weak relaxation processes have been detected under planar anchoring of molecules in the TGBA and TGBC* phases presumably due to amplitude (soft mode) and phase (Goldstone mode) fluctuations.

Słowa kluczowe

EN

TGB phases; dielectric relaxation; anisotropy; Goldstone and soft modes

• Wydawca: Stowarzyszenie Elektryków Polskich ; Polska Akademia Nauk ; Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
• Czasopismo: Opto-Electronics Review
• Rocznik: 2009
• Tom: Vol. 17, No. 2
• Strony: 144--149
• Opis fizyczny: Bibliogr. 31 poz., wykr., il.

Twórcy

autor

Dhar R.

autor

Pandey M. B.

autor

Pandey V. S.

autor

Pandey A. S.

autor

Das I. M. L.

autor

Achalkumar A. S.

autor

Yelamaggad C. V.

• Physics Department, University of Allahabad, Allahabad, 211 002, India,

Bibliografia

• [1] P. G. de Gennes, The Physics of Liquid Crystals, Oxford University Press, Oxford, 1975, P.G. de Gennes and J. Prost, 2nd ed., Oxford Science, Clarendon Press, Oxford 1993.
• [2] S. R. Renn and T.C. Lubensky, Abrikosov dislocation lattice in a model of cholesteric-to-smectic-A transition. Phys. Rev. A38, 2132-2147, 1988.
• [3] J. W. Goodby, M. A. Waugh, S. M. Stein, E. Chin, R. Pindak, and J. S. Patel: Characterization of a new helical smectic liquid crystal. Nature 337, 449-452, 1989.
• [4] O. D. Lavrentovich, Y. A. Nastishin, V. I. Kulishov, Y. S. Narkevich, and A. S. Tolochko: Helical smectic A. Europhys. Lett. 13, 313-318, 1990.
• [5] S. R. Renn: Multicritical behaviour of Abrikosov vortex lattices near the cholesteric-smectic-A-smectic-C* point. Phys. Rev. A45, 953-973, 1992.
• [6] K. J. Ihn, J. A. N. Zasadzinski, R. Pindak, A. J. Slaney, and J. W. Goodby: Observations of the liquid crystal analogue of the Abrikosov phase. Science 258, 275-278, 1992.
• [7] A. S. Petrenko, M. Hird, R. A. Lewis, J. G. Meier, J. C. Jones, and J. W. Goodby: A twist grain boundary phase with a local antiferroelectric structure. J. Phys: Condens. Mat. 12, 8577-8593, 2000.
• [8] R. Dhar: Twisted-grain-boundary (TGB) phases: nanostructured liquid-crystal analogue of Abrikosov vortex lattices. Phase Transit. 79, 175, 2006.
• [9] H. S. Kitzerow: Twist grain boundary phases. Chirality in Liquid Crystals, pp. 296-354, edited by H. S. Kitzerow and C. Bahr, Springer-Verlag, Berlin, 2001.
• [10] R. Dhar, M. B. Pandey, and V. K. Agrawal: Twisted grain boundary phases in the binary mixtures of 3 β-chloro-5-cholestene and 4-N-decyloxybenzoic acid. Phase Transit. 76, 763-780, 2003.
• [11] R. Dhar, M. B. Pandey, and V. K. Agrawal: Thermodynamical and optical studies of ternary mixtures of 4-n-heptyloxy benzoic acid, 4-n-decyloxy benzoic acid, and 5-cholesten 3 β-ol 3-octanoate”, Mol. Cryst. Liq. Cryst. 409, 269-284, 2004.
• [12] C. Girold, C. Legrand, N. Isaert, P. Pochat, J. P. Parneix, H. T. Nguyen, and C. Destrade: Dielectric investigation of the helical smectic A* (TGBA) SC* phase transition. Ferroelectrics 147, 171-157, 1993.
• [13] H. Xu, Y. P. Panarin, J. K. Vij, A. J. Seed, M. Hird, and J. W. Goodby: Investigations of the TGBA* phase in a ferrolectric liquid crystal using dielectric spectroscopy. J. Phys. Condens. Mat. 7, 7443-7452, 1995.
• [14] S. Wrobel, S. Hiller, M. Pfeiffer, M. Marzec, and W. Haase: Collective and molecular processes in a new class of ferroelectric liquid crystals. Liq. Cryst. 18, 21-29, 1995.
• [15] F. Bougrioua, N. Isaert, C. Legrand, A. Bouchta, P. Barois, and H. T. Nguyen: Dielectric properties of TGBA and TGBC phases. Ferroelectrics 180, 35-48, 1996.
• [16] S. L. Srivastava and R. Dhar: Dielectric anisotropy and AC conductivity of bicomponent mixtures of liquid crystals cholesteryl pelargonate and nonyloxybenzoic acid. Mol. Cryst. Liq. Cryst. 317, 23-26, 1998.
• [17] M. Ismaili, F. Bougrioua, N. Isaert, C. Legrand, and H. T. Nguyen: Dielectric properties of twist grain boundary phases. Influence of the anchoring and the distance between boundaries. Phys. Rev. E65, 011701, 2001.
• [18] M. B. Pandey: Study of the chiral phases of liquid crystals. D. Phil. Thesis, University of Allahabad, Allahabad, India, 2004.
• [19] M. Gupta, R. Dhar, V. K. Agrawal, R. Dabrowski, and M. Tykarska: Dielectric spectroscopy of a binary mixture of liquid crystals showing wide temperature twisted grain boundary phase with re-entrant cholesteric phase. Phys. Rev. E72, 021703, 2005.
• [20] M. R. Dodge, J. K. Vij, S. J. Cowling, A. W. Hall, and J. W. Goodby: Dielectric spectroscopy of the twist grain boundary phase and smectic-like behaviour in the isotropic phase. Liq.Cryst. 32, 1045-1051, 2005.
• [21] M. B. Pandey, R. Dhar, and W. Kuczynski: Dielectric investigations of induced twist grain boundary phases in the binary mixtures of cholesteryl benzoate and di-heptyloxyazoxybenzene. Ferroelectrics 343, 69-82, 2006.
• [22] C. V. Yelamaggad, A. S. Achalkumar, N. L. Bonde, and A. K. Prajapati: Liquid crystal Abrikosov flux phase: The exclusive wide thermal range enantiotropic occurrence. Chem. Mater. 18, 1076-1078, 2006.
• [23] M. B. Pandey, R. Dhar, A. S. Achalkumar, and C. V. Yelamaggad: Characteristic dielectric behaviour of the wide temperature range twist grain boundary phases of unsymmetrical liquid crystal dimmers. J. Phys. Condens. Mat. 19, 436219, 2007.
• [24] M. B. Pandey, R. Dhar, A. S. Achalkumar, and C. V. Yelamaggad: Frequency and temperature dependence of the dielectric parameters of wide temperature range TGBA and TGBC* phases of unsymmetrical liquid crystal dimmers. Phase Transit. 81, 449, 2008.
• [25] A. S. Pandey, R. Dhar, M. B. Pandey, A. S. Achalkumar, and C. V. Yelamaggad: Dielectric spectroscopy of unsymetrical liquid crystal dimers showing wide temperature range TGBA and TGBC* phases. Liq. Cryst. 36, 13-19, 2009.
• [26] M. B. Pandey, R. Dhar, V. K. Agrawal, and R. Dabrowski: Temperature dependence of dielectric behaviour of MHPB (H)PBC antiferroelectric liquid crystal. Mol. Cryst. Liq. Cryst. 414, 63-76, 2004.
• [27] M. B. Pandey, R. Dhar, V. K. Agrawal, R. Dabrowski, and M. Tykarska: Study of different modes of dielectric relaxation in a newly synthesized material exhibiting ferro-, ferri and antiferroelectric phases. Liq. Cryst. 31, 973-987, 2004.
• [28] V. S. Pandey, R. Dhar, A. K. Singh, A. S. Achalkumar, and C. V. Yelamaggad. 15th National Seminar on Ferroelectrics and Dielectrics, Thapar University, Patiala, India, 2008.
• [29] K. S. Cole and R. H. Cole: Dispersion and absorption in dielectrics. J. Chem. Phys. 9, 341-351, 1941.
• [30] M. B. Pandey, R. Dabrowski, and R. Dhar: Investigation of relaxation processes in anticlinic smectic C* (SmC*A) phase of liquid crystals by dielectric spectroscopy. Physica B387, 25-31, 2007.
• [31] S. L. Srivastava and R. Dhar: Characteristic time of ionic conductivity and electrode polarization. Ind. J. Pure Appl. Phys. 29, 745-751, 1991.