Tetragonal Phase of 6-Oxoverdazyl Bent-Core Derivatives with Photoinduced Ambipolar Charge Transport and Electrooptical Effects

Jasiński, Marcin; Pociecha, Damian; Monobe, Hirosato; Szczytko, Jacek; Kaszyński, Piotr

doi:10.1021/ja507594h

Cited by 37 publications

(42 citation statements)

References 35 publications

(54 reference statements)

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“…An experimental candidate for which such a piezoelectric coupling plays a role is ref. [13], where it was found that a tetragonal liquid crystalline phase (below two optically isotropic phases at higher temperatures) shows a linear response to an applied electric field. A natural explanation for the behavior observed would be an actual phase sequence isotropic liquid -T d phase -tetragonal phase with octupolar order.…”

Section: The Elastic εT D Phasementioning

confidence: 99%

“…In one case a liquid crystalline tetragonal phase showing a linear electro-optic effect was observed at lower temperatures [13], while in the other three cases Tschierske's group reported the existence of mesoscopic to macroscopic chiral domains of either hand in the lower temperature optically isotropic phase [14][15][16]. This observation was linked to the formation of clusters and or agglomerates of substantial size and associated with steric and packing interactions [14][15][16].…”

Section: Introductionmentioning

confidence: 97%

“…Quite recently isotropic-isotropic phase transitions have been observed for several compounds composed of achiral molecules with liquid crystalline phases following at lower temperatures [13][14][15][16][17]. In one case a liquid crystalline tetragonal phase showing a linear electro-optic effect was observed at lower temperatures [13], while in the other three cases Tschierske's group reported the existence of mesoscopic to macroscopic chiral domains of either hand in the lower temperature optically isotropic phase [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Brand

Pleiner

2017

Eur. Phys. J. E

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Abstract.We investigate the influence of transient or permanent elasticity on liquid phases with octupolar (tetrahedral) order, a question that has never been addressed before. The focus will be on optically isotropic liquid phases with tetrahedral order including the T d phase and the chiral T phase introduced by Fel. It turns out that the presence of both, a network as well as tetrahedral order can lead to the formation of chiral domains of both hands in an optically isotropic fluid due to a completely novel mechanism, thus providing a possible macroscopic explanation for recent experimental observations. We study in detail how elasticity influences the macroscopic dynamics of both, the T d and the T phase. The simultaneous presence of a transient network as well as of octupolar order is shown to lead to completely new crosscoupling phenomena for optically isotropic systems including transient dissipative elastic strains due to temperature gradients.

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Section: The Elastic εT D Phasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Brand

Pleiner

2017

Eur. Phys. J. E

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“…The statics is completed by adding up all the energy contributions ε = ε 0 + ε g + ε l + ε c +ε E , where ε 0 is the part of isotropic liquids andε E describes the influence of external fields (see below). The conjugate quantities then follow from ε as partial derivatives according to (73).…”

Section: Staticsmentioning

confidence: 99%

“…where h is the conjugate to , (73). The stress tensor carries the appropriate counter terms that guarantee zero entropy production.…”

Section: The Non-polar Orthorhombic D2 Tetrahedral Phasementioning

confidence: 99%

Tetrahedral Order in Liquid Crystals

Pleiner

Brand

2016

Braz J Phys

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We review the impact of tetrahedral order on the macroscopic dynamics of bent-core liquid crystals. We discuss tetrahedral order comparing with other types of orientational order, like nematic, polar nematic, polar smectic, and active polar order. In particular, we present hydrodynamic equations for phases, where only tetrahedral order exists or tetrahedral order is combined with nematic order. Among the latter, we discriminate between three cases, where the nematic director (a) orients along a fourfold, (b) along a threefold symmetry axis of the tetrahedral structure, or (c) is homogeneously uncorrelated with the tetrahedron. For the optically isotropic T d phase, which only has tetrahedral order, we focus on the coupling of flow with, e.g., temperature gradients and on the specific orientation behavior in external electric fields. For the transition to the nematic phase, electric fields lead to a temperature shift that is linear in the field strength. Electric fields induce nematic order, again linear in the field strength. If strong enough, electric fields can change the tetrahedral structure and symmetry leading to a polar phase. We briefly deal with the T phase that arises when tetrahedral order occurs in a system of chiral molecules. To case (a), defined above, belong (i) the non-polar, achiral, optically uniaxial D2d phase with ambidextrous helicity (due to a linear gradient Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth, Germany free energy contribution) and with orientational frustration in external fields, (ii) the non-polar tetragonal S4 phase, (iii) the non-polar, orthorhombic D2 phase that is structurally chiral featuring ambidextrous chirality, (iv) the polar orthorhombic C2v phase, and (v) the polar, structurally chiral, monoclinic C2 phase. Case (b) results in a trigonal C3v phase that behaves like a biaxial polar nematic phase. An example for case (c) is a splay bend phase, where the ground state is inhomogeneous due to a linear gradient free energy contribution. Finally, we discuss some experiments that show typical effects related to the existence of tetrahedral order. A summary and perspective is given.

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Light Tunable Gratings Based on Flexoelectric Effect in Photoresponsive Bent‐Core Nematics

Jing

Xiang

et al. 2019

Advanced Optical Materials

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A new photoresponsive bent‐core nematic (BCN) material, which exhibits flexoelectric domains (FDs) driven by electric field, is reported. Unexpectedly, it is found that the morphologies of FDs can be controlled by irradiation with light fields. This light tunability is ascribed to the photoisomerization effect of the azo moiety within the BCN molecules, where the ratio of trans and cis isomers changes according to the parameters of the light field, resulting in adjustable electric threshold and periodicity of FDs. Based on this principle, a prototype of controllable optical grating is assembeled, whose operation can be manipulated by the wavelength or intensity of light. Due to the easy, instant, and remote operation by light, this optical, contactless tunability has a great advantage over traditional electric control in tunable photonic devices.

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Tetragonal Phase of 6-Oxoverdazyl Bent-Core Derivatives with Photoinduced Ambipolar Charge Transport and Electrooptical Effects

Cited by 37 publications

References 35 publications

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Tetrahedral Order in Liquid Crystals

Light Tunable Gratings Based on Flexoelectric Effect in Photoresponsive Bent‐Core Nematics

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