Orientational Effects in Ferroelectric and Antiferroelectric Liquid Crystals using Infrared Spectroscopy

Kocot, A.; Vij, J. K.; Perova, T. S.

doi:10.1002/9780470141724.ch6

Cited by 13 publications

(4 citation statements)

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“…MHPSBO10 possesses two carbonyl groups associated with the thioester and the ester parts, respectively. ν(CO) vibrations along with the ν(CC) stretching in phenyls are probably the most important normal modes in the context of the ferroelectric liquid crystals studies, due to their reversal vibrational transitions geometry and, hence, their direct application potential in the orientational ordering studies. − Thus, the proper band assignment is essential in this case. According to the literature, for alkyl thiobenzoates, a ν(CO) band can be observed in the range ∼1675–1665 cm –1 .…”

Section: Resultsmentioning

confidence: 99%

“…It is believed that the local dipole moment associated with this molecular fragment underlies the spontaneous polarization phenomenon observed in ferro-/antiferroelectric liquid crystals. Hence, the vibration is of interest to many studies. − …”

Section: Resultsmentioning

confidence: 99%

“…It has been shown that vibrational spectroscopy of liquid crystals could be a very useful tool in a great number of phase transitions studies that can be investigated by both IR and Raman techniques. It has also been proven that the temperature dependent FT-IR spectroscopy of the aligned samples is an extremely valuable technique for exploration of the structure and order parameters in ferroelectric liquid crystals. − The similar studies, performed using Raman spectroscopy have been reported, e.g., by Fukuda and co-workers. − Two dimensional correlation analysis has also been proven to be a valuable supplementation of such experiments. , In all the cases an unambiguous knowledge of band assignment, their composition, and the related transition moment geometry is crucial. Because liquid crystal mesogens are one of the biggest size molecules studied by molecular orbitals calculations, the calculations were limited in quality for many years.…”

Section: Introductionmentioning

confidence: 89%

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Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy

et al. 2012

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The experimental and theoretical vibrational spectroscopic study of one of a novel antiferroelectric liquid crystals (AFLC), known under the MHPSBO10 acronym, have been undertaken. The interpretation of both FT-IR and FT-Raman spectra was focused mainly on the solid-state data. To analyze the experimental results along with the molecular properties, density functional theory (DFT) computations were performed using several modern theoretical approaches. The presented calculations were performed within the isolated molecule model, probing the performance of modern exchange-correlations functionals, as well as going beyond, i.e., within hybrid (ONIOM) and periodic boundary conditions (PBC) methodologies. A detailed band assignment was supported by the normal-mode analysis with SQM ab initio force field scaling. The results are supplemented by the noncovalent interactions analysis (NCI). The relatively noticeable spectral differences observed upon Crystal to AFLC phase transition have also been reported. For the most prominent vibrational modes, the geometries of the transition dipole moments along with the main components of vibrational polarizability were analyzed in terms of the molecular frame. One of the goals of the paper was to optimize the procedure of solid-state calculations to obtain the results comparable with the all electron calculations, performed routinely for isolated molecules, and to test their performance. The presented study delivers a complex insight into the vibrational spectrum with a noticeable improvement of the theoretical results obtained for significantly attracting mesogens using modern molecular modeling approaches. The presented modeling conditions are very promising for further description of similar large molecular crystals.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

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Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy

et al. 2012

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“…11,12 In solution, on the other hand, molecules are easily reoriented and the fieldinduced reorientation can be detected by the EA measurements. [13][14][15] However, the precise measurements of the EA spectra in solution are not so easy due to the difficulty in application of strong electric fields to solutions.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of electroabsorption spectra of polar and nonpolar organic molecules in solution and in a polymer film

Tayama

Iimori

Ohta

2009

The Journal of Chemical Physics

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Electroabsorption ͑EA͒ spectra of polar and nonpolar molecules of coumarin 153 ͑C153͒ and pyrene in solution and in a polymer film of polymethylmethacrylate ͑PMMA͒ have been measured in the UV-visible region at room temperature. The shape of the EA spectra of C153 in benzene, 1,4-dioxane, or monochlorobenzene remarkably depends on the angle between the polarization direction of the absorption light and the applied electric field, whereas the EA spectra of C153 doped in PMMA show only the Stark shift and the field-induced change in spectral shape is negligible. These results demonstrate that C153 is reoriented by application of electric fields in solution, but the molecules are immobilized in a PMMA film. Based on the EA spectra, electric dipole moments both in the ground state and in the excited state have been evaluated for C153 in different solvents. In the EA spectra of pyrene, only the Stark shift is observed both in solution and in PMMA, indicating that the field-induced molecular reorientation does not occur both in solution and in PMMA. The change in dipole moment of C153 as well as the change in molecular polarizability of pyrene following absorption is much larger in solution than that in PMMA.

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Introduction

Luckhurst¹,

Sluckin²

2015

Biaxial Nematic Liquid Crystals

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Orientational Effects in Ferroelectric and Antiferroelectric Liquid Crystals using Infrared Spectroscopy

Cited by 13 publications

References 50 publications

Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy

Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy

Comparative study of electroabsorption spectra of polar and nonpolar organic molecules in solution and in a polymer film

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