Landau model of the smectic C–isotropic phase transition

Mukherjee, Prabir K.; Pleiner, Harald; Brand, Helmut R.

doi:10.1063/1.1509055

Cited by 39 publications

(31 citation statements)

References 6 publications

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“…That fact is consistent with results presented in [37,38] and indicates that, in imines, S N < S A < S C takes place. Here S N , S A , and S C determine the ordering degree of nematic, SmA, and SmC mesophases, respectively.…”

Section: Resultssupporting

confidence: 94%

“…In these works a strongly first-order phase transition has been predicted. The SmC ↔ I phase transition has been experimentally investigated for various liquid crystalline materials in [47][48][49][50]. All these experiments showed the first-order character of the phase transition between the SmC mesophase and isotropic liquid.…”

Section: Resultsmentioning

confidence: 98%

“…The phase transition between the SmC mesophase and isotropic liquid was theoretically investigated in [38,47]. In these works a strongly first-order phase transition has been predicted.…”

Section: Resultsmentioning

confidence: 98%

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Thermotropic, Thermo-morphologic, and Thermo-optical Properties of New Smectogenic Calamitic Compounds Containing Imine Linking Groups

2011

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The synthesis and investigations of the mesomorphic, thermotropic, thermo-morphologic, and thermo-optical properties of two new salicylaldimine compounds, synthesized by our group, are reported in this work. Temperature transformations of specific textures of the smectic C mesophase, taking place in these compounds, and thermo-morphologic and thermotropic properties of the biphasic regions for direct and reverse phase transitions have been investigated. Temperature hysteresis and enlargement of the biphasic regions have been found. The character of texture transformations and temperature behavior of the optical birefringence indicate to the first order a smectic C-isotropic liquid-phase transition in these salicylaldimine compounds.

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Section: Resultssupporting

confidence: 94%

Section: Resultsmentioning

confidence: 98%

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Thermotropic, Thermo-morphologic, and Thermo-optical Properties of New Smectogenic Calamitic Compounds Containing Imine Linking Groups

2011

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“…This hysteresis is connected with the overheating and overcooling of liquid crystals. It was theoretically predicted in [15][16][17][18][19][24][25][26], is typical for firstorder phase transitions between the liquid crystalline mesophase and the isotropic liquid, and was experimentally observed by various scientists for different liquid crystals [12,[27][28][29][30][31][32].…”

Section: Discussionmentioning

confidence: 97%

Thermotropic and Thermo-optical Properties of Nematic Mesophase at Direct and Reverse Phase Transitions

2010

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Comparative investigations of the thermo-optical, thermotropic, and thermo-morphologic properties of aligned and non-aligned textures in the nematic mesophase over a large temperature interval and in regions of direct and reverse phase transitions between the nematic mesophase and the isotropic liquid have been carried out. The character of the optical transmission and adsorption coefficient has been compared with that of the texture transformations. Nonlinearity of the thermo-optical and thermotropic behavior at the nematic mesophase-isotropic liquid and isotropic liquid-nematic mesophase phase transitions has been observed. Differences in the temperatures of phase transitions for the aligned and non-aligned textures of the nematic liquid crystals have been found.

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“…Here, transition shifts and induced nematic order occur, which are linear in the field strength, (47), (49), (51), and (52). This also applies to tetrahedral-smectic transitions, since smectic order is always accompanied by nematic order [71]. Recently, isotropic-nematic transitions in bent-core material have been studied directly.…”

Section: Review Of the Experimental Situationmentioning

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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Landau model of the smectic C–isotropic phase transition

Cited by 39 publications

References 6 publications

Thermotropic, Thermo-morphologic, and Thermo-optical Properties of New Smectogenic Calamitic Compounds Containing Imine Linking Groups

Thermotropic, Thermo-morphologic, and Thermo-optical Properties of New Smectogenic Calamitic Compounds Containing Imine Linking Groups

Thermotropic and Thermo-optical Properties of Nematic Mesophase at Direct and Reverse Phase Transitions

Tetrahedral Order in Liquid Crystals

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