Orientation of alkyl chains and hindered rotation of carbonyl groups in the smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="italic">C</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">*</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math>phase of antiferroelectric liquid crystals studied by polarized Fourier transform infrared spectroscopy

Kim, Kyeong Hyeon; Ishikawa, Ken; Takezoe, Hideo; Fukuda, Atsuo

doi:10.1103/physreve.51.2166

Cited by 117 publications

(41 citation statements)

References 34 publications

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“…Formation of carbosilane sublayers leads to ferroelectric structure by weakening the tendency to parallel alignment of banana arms of molecules from the neighboring layers (entropic effect). Tendency for parallel packing of molecular arms is usually considered as a driving force for the antiferroelectric arrangement of transverse dipole moments in the consecutive layers [16,[25][26][27]. The sublayer formation, visible in both smectic phases by the appearance of additional X-ray signal at high angle region, is apparently more pronounced in the SmA d P F phase, as evidenced by high number of harmonics of the main signal related to the layer periodicity.…”

Section: Discussionmentioning

confidence: 99%

Ferroelectric behavior of orthogonal smectic phase made of bent-core molecules

et al. 2011

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Ferroelectric behavior in the recently reported orthogonal ferroelectric SmA d PF phase in an unsymmetric bent-core molecule with a carbosilane terminal group was studied. The ferroelectricity of the SmA d PF phase was unambiguously confirmed by optical second-harmonic generation (SHG) activity in the absence of an electric field, ferroelectric response, and high dielectric strength. The long-range polar order is a consequence of weakened interlayer coupling due to the formation of carbosilane sublayers, which allows for the parallel order of dipole moments of bent-core molecules in the neighboring layers. It develops in the system gradually through the second-order phase transition from the orthogonal SmA d phase. In the SmA d PF phase the strong surface anchoring results in the splay of polarization across the sample thickness. The polar surface anchoring also brings about strongly thickness dependent polar fluctuations, as proved by the dielectric measurements (Goldstone-like mode). The relaxation frequency and dielectric strength vary more than one order of magnitude with cell thickness; in particular the dielectric strength attains more than 2000 in a 25-µm-thick cell and continues to increase for thicker cells. Simple theory developed qualitatively explains the experimental results, supporting the polarization splay model proposed.

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Section: Discussionmentioning

confidence: 99%

Ferroelectric behavior of orthogonal smectic phase made of bent-core molecules

et al. 2011

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“…5 shows an example of the absorbance for the carbonyl group. Although the sinusoidal curve of absorbance with the minimum at ω = 0 should be obtained in conventional monomeric liquid crystals [5,6], the absorbance curve obtained in this study is not sinusoidal. Therefore, it is guessed that a domain structure having two alignments of the mesogenic parts including the carbonyl group may form both in the N and SmC A phases of the dimeric LC, which takes a bent molecular conformation.…”

Section: Resultsmentioning

confidence: 95%

“…In this study, the molecular alignment structure of both liquid-crystalline phases has been researched in detail with a polarized Fourier transform infrared spectroscopy (FT-IR). For an investigation of the molecular conformation and orientation, the polarized FT-IR can be used as a powerful tool [5,6]. The orientations of the function groups with which LC molecule forms can be…”

Section: Introductionmentioning

confidence: 99%

Molecular alignment structure of dimeric liquid crystals

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et al. 2005

Materials Science and Engineering: B

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“…The results of FTIR spectroscopy shows that the rotation of both chiral and core carbonyl C=O groups aroind the long molecular axis is hindered in tilted smectic phases [48-5 11. The investigation of the switching mechanism under application of electric f eld by time-resolved FTIR spectroscopy [48] shows that all the molecular segments reorient simultaneously, at least in the microsecond Iange. These methods do not provide direct information about the structure of ferrielectric phases; however, a careful analysis of the experimental results enables a validation of the structure of some phases, such as SmCi and even SmC; [47].…”

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confidence: 99%