Dielectric studies of the soft mode and Goldstone mode in ferroelectric liquid crystals

Gouda, F.; Skarp, Kent; Lagerwall, S. T.

doi:10.1080/00150199108014063

Cited by 255 publications

(96 citation statements)

References 39 publications

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“…One can conclude, on the basis of our dielectric results, that the dielectric relaxation processes observed by us in the 2-CO compounds are similar to those of the Goldstone mode and the soft mode classically observed in the SmC* and SmA* phases by others [4]. Our precise experiments do not confirm the existence of an additional relaxation mechanism in the SmC* phase of 2-CO compound [2].…”

Section: Discussioncontrasting

confidence: 49%

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Rutkowska

Perkowski

Piecek

et al. 2008

Opto-Electronics Review

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Dielectric measurements were performed for two smectogens, being structurally analogous with the opposite space orientation of the-COO ester group in the molecular core, using a HP4192A impedance analyser. Gold coated electrode cells of different thicknesses were used. Temperature dependences of the relaxation frequency fR and the inverse of the dielectric strength Δε′┴ −1 obtained by fitting experimental values of perpendicular components, i.e., the real ε′┴ and the imaginary ε″┴ parts of the complex dielectric permittivity to the Cole-Cole equation as well as the investigation of modification of relaxation processes under bias were determined for the SmC*, SmA*, and N* phases of studied compounds. One can conclude, on the basis of the above results, that dielectric relaxation processes observed by us in the studied compounds are similar to those of the soft and Goldstone mode typically observed by others in the SmC*, SmA*, and N* phases. It is concluded from acomparison of their properties with other related compounds that the link between the biphenyl moiety and-COO ester group is closely related to the stability of smectic phases.

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Section: Discussioncontrasting

confidence: 49%

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Rutkowska

Perkowski

Piecek

et al. 2008

Opto-Electronics Review

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“…This ITO effect on dielectric measurements also has been reported elsewhere. 24 Figure 2(a) shows the Cole-Cole diagrams at two different temperatures, one in the SmC * phase (2 below T c ) and another in the SmA * phase (2 above T c ) for ZnO NP doped ELC material, while Fig. 2(b) shows the Cole-Cole plots for pure ELC material 2 below T c in SmC * and 3 above T c in SmA * phases, respectively.…”

Section: Resultsmentioning

confidence: 99%

Effect of ZnO nanoparticles on the SmC-SmA phase transition temperature in electroclinic liquid crystals

Malik

Choudhary

Silotia

et al. 2011

Journal of Applied Physics

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Experimental assessment of quasi-binary picture of thermotropics: Induced smectic A phase in 7CB-n-heptane system J. Chem. Phys. 135, 044705 (2011) Does transparent nematic phase exist in 5CB/DDAB/water microemulsions? From the viewpoint of temperature dependent dielectric spectroscopy J. Chem. Phys. 134, 034505 (2011) A kind of two-dimensional electroconvection at ultralow electric frequency Appl. Phys. Lett. 97, 203507 (2010) Study of the isotropic to smectic-A phase transition in liquid crystal and acetone binary mixtures J. Chem. Phys. 133, 174501 (2010) Thermotropic nematic and smectic order in silica glass nanochannels Appl. Phys. Lett. 97, 153124 (2010) Additional information on J. Appl. Phys. ZnO nanoparticles (NPs), synthesized in an alcoholic medium at room temperature, were added to electroclinic liquid crystal (ELC) materials. The addition of ZnO NPs in ELCs, caused a remarkable shift in SmC * -SmA * phase transition which was investigated from the dielectric and electro-optical measurements. The anchoring of ELC molecules around ZnO NPs creates orientational distortions near the surface, which may give additional ordering to the ELC molecular arrangement. After analyzing collective dielectric relaxation processes of ZnO NP doped ELCs, three distinct loss peaks were observed. The different behavior of ZnO NP doped ELC from pure ELC has been explained by determining the dielectric strength, the distribution parameter and the corresponding relaxation frequency, and so on, and then these results have been compared with the data calculated by using the theoretical model. The effect of ZnO NPs addition on physical parameters, such as spontaneous polarization (P s ) and rotational viscosity (g) has also been observed.

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“…Consequently, the dielectric and optical response methods yield inconsistent result at high frequencies. Another discrepancy between dielectric and optical response data occur at low, or very low, field frequencies (region III), for which ionic currents give significant contributions to the dielectric response [14,15]. On the contrary, the optical response is nearly unaffected by ionic currents, even at very low frequencies.…”

Section: Resultsmentioning

confidence: 91%

Comparison of dielectric and optical responses of chevron ferroelectric liquid crystals

Jeżwski

Kuczyński

Hoffmann

et al. 2008

Opto-Electronics Review

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An analysis of consistency of dielectric and optical response methods is carried out for surface stabilized ferroelectric liquid crystals (SSFLC) with chevron geometry. The consistency is found both theoretically and experimentally for weak external electric fields of intermediate frequencies, for which the response of SSFLC is dominated by collective relaxation processes due to azimuthal reorientation of molecules arranging chevron layers. The methods are experimentally shown to lack consistency within very low, relatively low, and high field-frequency ranges. The disagreement appearing at relatively low frequencies is argued to be a consequence of different recording by dielectric and optical techniques the dynamics of zig-zag walls, forming defects in chevron structure.

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Dielectric studies of the soft mode and Goldstone mode in ferroelectric liquid crystals

Cited by 255 publications

References 39 publications

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Effect of ZnO nanoparticles on the SmC-SmA phase transition temperature in electroclinic liquid crystals

Comparison of dielectric and optical responses of chevron ferroelectric liquid crystals

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Dielectric studies of the soft mode and Goldstone mode in ferroelectric liquid crystals

Cited by 255 publications

References 39 publications

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals

Comparison of dielectric and optical responses of chevron ferroelectric liquid crystals

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Effect of ZnO nanoparticles on the SmC-SmA phase transition temperature in electroclinic liquid crystals