Effect of terminal polar substituents on the nature of smectic A liquid crystals of a series of 4-(4″-octyloxybenzoyloxy)benzylidene-4′-substituted anilines

Miyajima, Seiichi; Nakazawa, Kôzô; Niikura, Keiko; Ujiiye, Yasuhiro; Yashiro, Makiko; Chiba, Takehiko

doi:10.1080/02678299008047382

Cited by 9 publications

(3 citation statements)

References 24 publications

(9 reference statements)

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“…0.44 in the smectic A phase of hexakis(4-(4‘-dodecyl)biphenoxy)cyclotriphosphazene . This value is smaller than that found for the usual smectic A liquid crystals, , suggesting a relatively high disordering of the cyclotriphosphazene ring in the smectic A phase. The similar situation is considered to occur in the Sc phase of the HOCP.…”

Section: Resultscontrasting

confidence: 62%

Thermal and Structural Study on Liquid-Crystalline Phase Transition in Hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene

et al. 1997

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A series of hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene [PN(OC6H4C6H4OC) n H2 n +1)2]3 (HACP, n = 6−12) compounds was synthesized from sodium salts of 4-alkyloxy-4‘-hydroxybiphenyl and hexachlorocyclotriphosphazene. The phase transition and mesogenicity of these substances were studied by FT-IR, X-ray diffraction, and DSC measurements and polarizing microscope observations. In the crystalline-to-smectic C phase transition of HACP with n = 8, the infrared bands of PN and P−O−(C) stretching vibrations were found to shift to the lower frequency, indicating the weakening of the cyclotriphosphazene ring in the liquid-crystalline phase. The X-ray analyzed interlayer spacing 36 Å is smaller than the value expected for the fully extended molecular model, indicating that the tilt angle of the molecules is about 35° from the normal to the layer plane. For HACP with n = 6, monotropic nematic and smectic C phases were found to appear only in the cooling process. Enantiotropic N and Sc phases were found for the n = 7 member. For the HACP with the n = 8−12, only an enantiotropic Sc phase was detected. In the series of HACP, the temperature range of the mesomorphic phase increased with an increase in n. The odd−even effect was not clear, originating from the peculiar shape of the hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene with three side chains pointing three upward and three downward in both sides of the cyclotriphosphazene ring.

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Section: Resultscontrasting

confidence: 62%

Thermal and Structural Study on Liquid-Crystalline Phase Transition in Hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene

et al. 1997

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“…The chosen solution is the one that give the lowest value for the free energy in eq. (35). A phase transition occurs at the point at which one or more order parameters change from a zero to a non-zero value as the temperature is lowered.…”

Section: E Methodsmentioning

confidence: 99%

“…This approximation in principle has only limited validity, but in practice has been used with a good degree of success (see e.g. 35,36 ). The functions f (θ) and g(z) are each independently normalized:…”

Section: B Mcmillan Theory Of Smecticsmentioning

confidence: 99%

Molecular field theory for biaxial smectic A liquid crystals

Sluckin

Luckhurst

2013

The Journal of Chemical Physics

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Thermotropic biaxial nematic phases seem to be rare, but biaxial smectic A phases less so. Here we use molecular field theory to study a simple two-parameter model, with one parameter promoting a biaxial phase and the second promoting smecticity. The theory combines the biaxial Maier-Saupe and McMillan models. We use alternatively the Sonnet-Virga-Durand (SVD) and geometric mean approximations (GMA) to characterize molecular biaxiality by a single parameter. For non-zero smecticity and biaxiality, the model always predicts a ground state biaxial smectic A phase. For a low degree of smectic order, the phase diagram is very rich, predicting uniaxial and biaxial nematic and smectic phases, with the addition of a variety of tricritical and tetracritical points. For higher degrees of smecticity, the region of stability of the biaxial nematic phase is restricted and eventually disappears, yielding to the biaxial smectic phase. Phase diagrams from the two alternative approximations for molecular biaxiality are similar, except inasmuch that SVD allows for a first-order isotropic-biaxial nematic transition, whereas GMA predicts a Landau point separating isotropic and biaxial nematic phases. We speculate that the rarity of thermotropic biaxial nematic phases is partly a consequence of the presence of stabler analogous smectic phases.

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Crystalline smectic E phase revisited in case of symmetrical dibenzo-18-crown-6-ether azomethine dimers

Cozan

Ardeleanu

Airinei

et al. 2018

Journal of Molecular Structure

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Effect of terminal polar substituents on the nature of smectic A liquid crystals of a series of 4-(4″-octyloxybenzoyloxy)benzylidene-4′-substituted anilines

Cited by 9 publications

References 24 publications

Thermal and Structural Study on Liquid-Crystalline Phase Transition in Hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene

Thermal and Structural Study on Liquid-Crystalline Phase Transition in Hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene

Molecular field theory for biaxial smectic A liquid crystals

Crystalline smectic E phase revisited in case of symmetrical dibenzo-18-crown-6-ether azomethine dimers

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