Low transition temperature organosiloxane liquid crystals displaying a de Vries smectic A phase

Naciri, Jawad; Carboni, C.; George, A. K.

doi:10.1080/0267829021000060250

Cited by 30 publications

(31 citation statements)

References 13 publications

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“…3 Later on it was found that the electroclinic effect could also be possible in tilted Sm-A phase in which although the molecules are tilted in Sm-A phase but the individual layer polarization is zero due to randomization of tilt in each layer. [4][5][6][7][8] These are the de Vries liquid crystals reported by Diele et al, 9 and later explained by de Vries in 1974. 10 Diele et al had obtained layer spacing, which was temperature independent for a number of compounds but at that time people failed to consider the wider implications of his findings.…”

Section: Introductionmentioning

confidence: 99%

A dielectric mode in electroclinic liquid crystals

Thakur

Choudhary

Kaur

et al. 2006

Journal of Applied Physics

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The dielectric properties of electroclinic and ferroelectric liquid crystal materials have been investigated in the frequency range of 100 Hz-10 MHz. A dielectric mode has been predicted in electroclinic liquid crystals near the transition temperature of Sm-C * -Sm-A phase. It has been observed that the investigated material has nonlayer shrinkage near the transition temperature of Sm-C * -Sm-A phase and shows anomalous behavior of dielectric spectra, tilt, and texture which is entirely different from the behavior of ferroelectric liquid crystals ͑FLCs͒. The dielectric relaxation frequency and tilt angle are almost constant with respect to temperature near the transition temperature under high bias field, which is characteristically different from FLCs. The high dielectric permittivity near T c owing to the presence of mode contribution leads to the fact that there is an intralayer phason variation few degrees before transition. The mode has been named random mode due to its origin from randomization of tilt near T c . Tilt randomization has been considered as an order parameter because in both the phases molecules are tilted but it is disordered in Sm-A phase making its intralayer polarization zero.

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Section: Introductionmentioning

confidence: 99%

A dielectric mode in electroclinic liquid crystals

Thakur

Choudhary

Kaur

et al. 2006

Journal of Applied Physics

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“…In these devices, large layer-shrinkage causes chevron defects and bright zigzag lines, which have hindered their commercialization for decades. Consequently, a large number of de Vries smectic mesogens have been synthesized [8][9][10][11] in recent years. Generally, these mesogens have either a perfluorinated or a siloxane segment in one of the end chains that tends to nanosegregate and enhance lamellar order, which is believed to promote the de Vries behavior [12][13][14].…”

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confidence: 99%

Direct Observation of Diffuse Cone Behavior in de Vries Smectic-Aand -CPhases of Organosiloxane Mesogens

et al. 2011

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“…Chiral bimesogen organosiloxane liquid crystal materials present the enigmatic characteristic of behaving either as a low molar mass material where the molecule responds as a whole unit to external stimuli or as a side-chain polymer where the two lateral mesogenic pendants respond independently of each other [1][2][3]. In the latter case a change in the conformation of the molecule is associated to the response.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron X-ray investigation of the layer spacing in a series of low molar mass bi-mesogen organosiloxane smectic materials

Carboni

Jozić

et al. 2014

Phase Transitions

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The temperature dependence of the layer spacing of a series of chiral bi-mesogen organosiloxane liquid crystal materials is presented. The detailed measurements were taken at the Elettra Sincrotrone radiation source in Trieste on thin specimens contained between glass coverslips. In the materials with 10 and 11 spacers between the siloxane and the mesogenic moiety it is observed that the temperature dependence of the layer spacing is not monotonous. In the material with 6 spacers there is an abrupt change of 0.01 nm in the layer spacing between 35 and 36 o C. In this temperature range domains with both layer spacing coexist. This observation is in agreement with polarised light microscopy observations however, detailed DSC measurements show no heat associated with this transition.

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Low transition temperature organosiloxane liquid crystals displaying a de Vries smectic A phase

Cited by 30 publications

References 13 publications

A dielectric mode in electroclinic liquid crystals

A dielectric mode in electroclinic liquid crystals

Direct Observation of Diffuse Cone Behavior in de Vries Smectic-Aand -CPhases of Organosiloxane Mesogens

Synchrotron X-ray investigation of the layer spacing in a series of low molar mass bi-mesogen organosiloxane smectic materials

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