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Yadav N, Panov VP, Swaminathan V, Sreenilayam SP, Vij JK, Perova TS, Dhar R, Panov A, Rodriguez-Lojo D, Stevenson PJ. Chiral smectic-A and smectic-C phases with de Vries characteristics. Phys Rev E 2017; 95:062704. [PMID: 28709233 DOI: 10.1103/physreve.95.062704] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Indexed: 11/07/2022]
Abstract
Infrared and dielectric spectroscopic techniques are used to investigate the characteristics of two chiral smectics, namely, 1,1,3,3,5,5,5-heptamethyltrisiloxane 1-[4^{'}-(undecyl-1-oxy)-4-biphenyl(S,S)-2-chloro-3-methylpentanoate] (MSi_{3}MR_{11}) and tricarbosilane-hexyloxy-benzoic acid (S)-4'-(1-methyl-hexyloxy)-3'-nitro-biphenyl-4-yl ester (W599). The orientational features and the field dependencies of the apparent tilt angle and the dichroic ratio for homogeneous planar-aligned samples were calculated from the absorbance profiles obtained at different temperatures especially in the smectic-A* phase of these liquid crystals. The dichroic ratios of the C-C phenyl ring stretching vibrations were considered for the determination of the tilt angle at different temperatures and different voltages. The low values of the order parameter obtained with and without an electric field applied across the cell in the Sm-A^{*} phase for both smectics are consistent with the de Vries concept. The generalized Langevin-Debye model introduced in the literature for explaining the electro-optical response has been applied to the results from infrared spectroscopy. The results show that the dipole moment of the tilt-correlated domain diverges as the transition temperature from Sm-A^{*} to Sm-C^{*} is approached. The Debye-Langevin model is found to be extremely effective in confirming some of the conclusions of the de Vries chiral smectics and gives additional results on the order parameter and the dichroic ratio as a function of the field across the cell. Dielectric spectroscopy finds large dipolar fluctuations in the Sm-A^{*} phase for both compounds and again these confirm their de Vries behavior.
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Affiliation(s)
- Neelam Yadav
- Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland.,Centre of Material Sciences, University of Allahabad, Allahabad 211002, India
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - T S Perova
- Microelectronics Group, Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
| | - R Dhar
- Centre of Material Sciences, University of Allahabad, Allahabad 211002, India
| | - A Panov
- School of Chemistry & Chemical Engineering, Queens University, Belfast BT7 1NN, United Kingdom
| | - D Rodriguez-Lojo
- School of Chemistry & Chemical Engineering, Queens University, Belfast BT7 1NN, United Kingdom
| | - P J Stevenson
- School of Chemistry & Chemical Engineering, Queens University, Belfast BT7 1NN, United Kingdom
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Scaife BKP, Sigarev AA, Vij JK, Goodby JW. Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission of liquid crystals: comparison with experiments. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:021704. [PMID: 19792143 DOI: 10.1103/physreve.80.021704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Indexed: 05/28/2023]
Abstract
The theory of the absorbance of a semi-infinite medium characterized by a second-rank dielectric tensor for the entire electromagnetic spectrum, as given by Scaife and Vij [J. Chem. Phys. 122, 174901 (2005)], is extended to include molecules of prolate spheriodal shape with longitudinal and transverse polarizabilities and to cover the case of elliptically polarized incident radiation. The theory is applied to the infrared transmission experiments of biaxial liquid crystals. It is found that the formula for the dependence on frequency and on angle of polarization of the absorbance A(omega,theta)= -log(10)[10(A(omega,0)) cos(2) theta + (10(-A(omega,pi/2)) sin(2) theta)] is unaffected by the anisotropy of the molecules and by the elliptical polarization of the incident radiation. A small (+/-5%) discrepancy between theory and experiment has been found for bands with high absorbances. It is found that this discrepancy does not depend on birefringence of the sample but may depend on the precise method of absorbance measurement and on effects at the surface of the cell containing the liquid crystal under test.
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Affiliation(s)
- B K P Scaife
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Lee SC, Chang JY. Preparation of Layered Polymer Networks by Cross-Linking Reaction of a Liquid Crystalline Polyphosphazene in a Smectic Phase. Macromolecules 2009. [DOI: 10.1021/ma900405t] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Seung Cheol Lee
- Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-744, Korea
| | - Ji Young Chang
- Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-744, Korea
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Sigarev AA, Vij JK, Hall AW, Cowling SJ, Goodby JW. Molecular orientational properties of a high-tilt chiral smectic liquid crystal determined from its infrared dichroism. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:051707. [PMID: 18233673 DOI: 10.1103/physreve.76.051707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Revised: 08/02/2007] [Indexed: 05/25/2023]
Abstract
The orientational characterisitics and the temperature dependencies of the molecular apparent tilt angle of a partly fluorinated chiral smectic liquid crystal (/S/)-4-(1-methylheptyloxycarbonyl)phenyl 4'-[6-(3,4,4,4-tetrafluoro-3-trifluoromethylbutylcarbonyloxy)hexyloxy] biphenyl-4-carboxylate (acronym MHPHFHHOBC) are studied using the polarized Fourier transform infrared (FTIR) spectroscopy. The molecular orientational distributions and the orientational order parameters for a homogeneously aligned liquid crystalline sample at various temperatures and external electric fields are examined. The analysis uses the dichroic parameters of the phenyl and the carbonyl bands. For a temperature range of 65-80 degrees C corresponding to the antiferroelectric SmCA* phase, the molecular apparent tilt angle lies within the range 43 degrees -44 degrees; antiferroelectric smectic structure being rather close to the orthoconic SmCA* phase. An application of sufficiently high dc field across the cell in its SmA* phase surprisingly shows that the dichroism first increases slowly and then rapidly in two stages and finally a saturated apparent tilt angle of approximately 30 degrees is reached. The IR dichroic data is used to estimate the polar angles and the degree of rotational biasing of the carbonyl groups with respect to the molecular long axis. In the SmA* phase, the sample appears to demonstrate some of the typical properties of a de Vries material.
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Affiliation(s)
- A A Sigarev
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Huang JY, Shih WT. Probing field-induced submolecular motions in a ferroelectric liquid crystal mixture with time-resolved two-dimensional infrared spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:7593-7603. [PMID: 21690872 DOI: 10.1088/0953-8984/18/32/008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Time-resolved two-dimensional infrared (2D IR) spectroscopy has been applied to analyse an electro-optic switching ferroelectric liquid crystal (FLC) mixture. The 2D IR correlation technique clearly shows that the Goldstone mode in the SmC* phase is suppressed by an applied electric field. The field-induced reorientation process initiates from intramolecular motions in about 10 µs. The intramolecular motions then propagate from the molecular segments attached to the same molecule to those fragments on other surrounding molecules. During the field-induced switching, the IR dipoles undergo a collective reorientation but with hindered rotation about the molecular long axis.
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Affiliation(s)
- Jung Y Huang
- Department of Photonics and Institute of Electro-Optical Engineering, Chiao Tung University, Hsinchu 305, Taiwan, Republic of China
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Korlacki R, Fukuda A, Vij JK, Kocot A, Görtz V, Hird M, Goodby JW. Self-assembly of biaxial ordering and molecular tilt angle of chiral smectic liquid crystals in homeotropically aligned cells investigated using infrared spectroscopy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:041704. [PMID: 16383399 DOI: 10.1103/physreve.72.041704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 04/21/2005] [Indexed: 05/05/2023]
Abstract
Temperature dependences of the infrared absorbance have been measured for the four chiral liquid crystal samples in the homeotropic cell configuration. It is shown that the values of the orientational order parameter obtained using this method exhibit a remarkable similarity to the x-ray diffraction results of the smectic layer spacing and lead to accurate values of the molecular tilt angle. This has important consequences for the existing interpretation of the x-ray data. The proposed method, in many cases, may be considered as a valuable alternative to the x-ray diffraction, giving additional, important information about the orientations and the ordering of the molecular fragments. It is found that if the experimentally obtained order parameter is low, then the molecular biaxiality is exceptionally large. The average phenyl ring plane is found to lie close to the molecular tilt plane.
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Affiliation(s)
- R Korlacki
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Scaife BKP, Vij JK. Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals. J Chem Phys 2005; 122:174901. [PMID: 15910063 DOI: 10.1063/1.1874833] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The theory of absorbance is developed for the entire electromagnetic spectrum of radiation in a semi-infinite anisotropic medium with a second rank dielectric tensor, the elements of which are complex and frequency dependent. The theory of the absorbance A(omega,theta) of an optically anisotropic liquid in an infrared (IR) test cell is then outlined and applied to IR transmission experiments. A formula for the dependence of A(omega,theta), on theta (theta being the angle between the electric vector and the principal optical axis) is derived from first principles. The formula, for radiation of angular frequency omega, viz, A(omega,theta)=-log(10)[10(-A(omega,0))cos(2)theta+10(-A(omega,pi2))sin(2)theta] is in agreement with that proposed by Jang, Park, Maclennan, Kim, and Clark [Ferroelectrics 180, 213 (1996) ] and confirms some of the work of Kocot, Wrzalik, and Vij [Liq. Cryst. 21, 147 (1996)]. The comments on this formula by Jang, Park, Kim, Glaser, and Clark [Phys. Rev. E 62, 5027 (2000)], and by Kocot et al. are discussed. The absorbance A(omega,0) and A(omega,pi2) have been expressed in terms of the optical properties of the material and the dimensions of the cell.
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Affiliation(s)
- B K P Scaife
- Laboratory of Advanced Materials, Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Ireland
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Hayashi N, Kato T, Fukuda A, Vij JK, Panarin YP, Naciri J, Shashidhar R, Kawada S, Kondoh S. Evidence for de Vries structure in a smectic-A liquid crystal observed by polarized Raman scattering. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:041705. [PMID: 15903689 DOI: 10.1103/physreve.71.041705] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2003] [Revised: 07/26/2004] [Indexed: 05/02/2023]
Abstract
The second- and fourth-order apparent orientational order parameters of the core part of the molecule P2 (app) and P4 (app) , have been measured by polarized vibrational Raman spectroscopy for a homogeneously aligned ferroelectric smectic liquid crystal with three dimethyl siloxane groups in the achiral terminal chain, which shows de Vries-type phenomena, i.e., very large electroclinic effect in the smectic- A (Sm-A) phase and a negligible layer contraction at the phase transition between the Sm-A and Sm- C(*) phases. The apparent orientational order parameters of the rigid core part of the molecule are extremely small both with and without the external electric field in Sm-A . These results provide evidence for the existence of the de Vries Sm-A phase, where the local molecular director is tilted at a large angle.
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Affiliation(s)
- Naoki Hayashi
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan.
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