Evolution of the boulder model for the molecular origins of the polarization in ferroelectric liquid crystals

Walba, David M.; Razavi, Homaune A.; Horiuchi, Akiko; Eidman, Kirk F.; Otterholm, Bengt; Haltiwanger, R. C.; Clark, Noel A.; Shao, Renfan; Parmar, D. S.; Wand, Michael; Vohra, Rohini T.

doi:10.1080/00150199108014054

Cited by 24 publications

(5 citation statements)

References 12 publications

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“…The zig-zag model has also been implemented in the Boulder model by Walba and Clark to explain the polarization of ferroelectric liquid crystals. [115][116][117] According to this model an increase of the non-tilted alkyl chains should lead to a smaller layer contraction at the SmA-SmC phase transition.…”

Section: Investigation Of De Vries-like Properties Of the Uorenone Ilcsmentioning

confidence: 99%

Fluorenone imidazolium salts as novel de Vries materials

et al. 2020

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Section: Investigation Of De Vries-like Properties Of the Uorenone Ilcsmentioning

confidence: 99%

Fluorenone imidazolium salts as novel de Vries materials

et al. 2020

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“…In the homologous series KNnm, the electroclinic tilt angle of the SmA phase can be increased by making the hydrocarbon chains longer, thus making the molecules more oblique. Second, the Boulder model for ferroelectric liquid crystals shows that molecules in the SmC phase typically take the shape of bent cylinders [9]. For that reason, we can regard this shape as a generic feature of smectic liquid crystals.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulation of smectic liquid crystals and the electroclinic effect: The role of molecular shape

Selinger

et al. 1999

Phys. Rev. E

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Using Monte Carlo simulation methods, we explore the role of molecular shape in the phase behavior of liquid crystals and the electroclinic effect. We study a "bent-rod" mesogen shaped like the letter Z, composed of seven soft spheres bonded rigidly together with no intra-molecular degrees of freedom. For strongly angled molecules, we find that steric repulsion alone provides the driving force for a smectic-C phase, even without intermolecular dipole-dipole interactions. For weakly angled (nearly rod-like) molecules, we find a stable smectic-A (SmA) phase and a strong electroclinic effect with a saturation tilt angle of about 19• . In the SmA phase we find evidence of vortex-like point defects. We also observe a field-induced nematic-smectic phase transition.

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“…Thus it could be hypothesized that the switching is SmCP R -like and the development of polar order, leading to an increased polar domain size in the SmC a P R * phase, is supported by the applied electric field and the chiral recognition in the layers. 85 This means that the switching process is mainly based on the polar order of the bent cores. Also the relatively high polarization value is in line with a bent-core based switching process for this kind of molecules, with a stereogenic centre in the terminal alkyl chain being only weakly coupled with the aromatic core.…”

Section: And S5a Esi †)mentioning

confidence: 99%

Development of tilt, biaxiality and polar order in bent-core liquid crystals derived from 4′-hydroxybiphenyl-3-carboxylic acid

et al. 2015

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A homologous series of unsymmetric bent-core compounds derived from 4 0 -hydroxybiphenyl-3carboxylic acid and having strongly distinct chains at both ends has been synthesized and characterized.The liquid crystalline self-assembly of the compounds was investigated by differential scanning calorimetry, optical polarizing microscopy, X-ray scattering and electro-optic methods. With increasing chain length and upon cooling a series of smectic phases was observed, starting from SmA phases having an unusual structure composed of domains with a randomized tilt direction. This is followed by a series of biaxial smectic phases, involving a smectic phase composed of tilt domains with increased size (SmC r ), anticlinic and synclinic tilted smectic phases (SmC s , SmC a ) and finally columnar phases with an oblique (Col obl ) or pseudo-rectangular (Col rec ) lattice. This phase sequence is the result of the competition between an emerging tilt, the dense packing of the bent aromatic cores leading to restricted rotation and contributing to phase biaxiality, and the steric distortion of the dense packing by the bulky 3,7-dimethyloctyloxy chains, inhibiting the formation of long range polar order. In all smectic phases the tilt is relatively small, thus providing only weak layer coupling and this provides the basis for sensitive regulatory networks determining the mode of molecular self-assembly in the resulting LC phases. The columnar phases have a tilted B 1rev -like ribbon structure with a temperature and chain length dependent inversion of the sign of birefringence. Though none of the racemic compounds show polar switching, the (S)-enantiomer of one compound shows ferroelectric-like switching in an anticlinic tilted smectic phase (SmC a P R *).

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Evolution of the boulder model for the molecular origins of the polarization in ferroelectric liquid crystals

Cited by 24 publications

References 12 publications

Fluorenone imidazolium salts as novel de Vries materials

Fluorenone imidazolium salts as novel de Vries materials

Monte Carlo simulation of smectic liquid crystals and the electroclinic effect: The role of molecular shape

Development of tilt, biaxiality and polar order in bent-core liquid crystals derived from 4′-hydroxybiphenyl-3-carboxylic acid

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