Dielectric studies of the hexatic B-smectic A and crystal B-smectic A transitions

Nagabhushan, C.; Nair, Geetha G.; Ratna, B. R.; Shashidhar, R.; Goodby, J. W.

doi:10.1080/02678298808086364

Cited by 21 publications

(5 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the observed low-frequency relaxation mechanism involves reorientation of the longitudinal molecular dipole in the external field about its short axis. The observed range of relaxation frequencies at different temperatures in the nematic phase are in the range of reported (Srikantha and Madhusudhana, 1984;Bhushan et al, 1988;Padmaja-Rani et al, 1994) values in other NLCs. The temperature variation of the nematic relaxation frequency is presented through the reduced temperature (Arrhenius) plots in Fig.…”

Section: Methodssupporting

confidence: 64%

Study of dipole dynamics and pre-transitional effects at isotropic to nematic phase transition by low-frequency dielectric relaxation measurements

et al. 2003

View full text Add to dashboard Cite

Thermal microscopy (TM) as well as low-frequency (LF) dielectric relaxation studies are carried out on a nematic liquid crystal (NLC), viz E7 (Merck Ltd, UK). The isotropic to nematic (IN) transition temperature T IN determined by TM and LF-dielectric permittivity measurements agrees with the available data. Dielectric loss studies in the frequency region of 5-10 MHz indicate a relaxation (in the kHz region) akin to Debye type off-centered dispersion. The observed nematic relaxation is found to correspond to reorientation (about the short axis) of the nematic dipole to the external field. The temperature variation of the nematic relaxation frequency f R is found to follow an Arrhenius shift, with an activation energy of 1.7 eV. Temperature variation of the dielectric strength (Á" ¼ " o À " 1 ) and the distribution parameter in the nematic phase are discussed. The dynamic response of the nematic dipoles and growth of pre-transitional fluctuations are found to be nonlinear in the vicinity of the IN transition. The value of the exponent eff ¼ 0.072 indicates weak growth of transitional fluctuations across the IN transition.

show abstract

Section: Methodssupporting

confidence: 64%

Study of dipole dynamics and pre-transitional effects at isotropic to nematic phase transition by low-frequency dielectric relaxation measurements

et al. 2003

View full text Add to dashboard Cite

show abstract

“…Solid line has a fitting correlation coefficient (R 2 ) of 0.9921, whereas for broken lines R 2 values are 0.9961 (higher temperature side) and 0.9894 (lower temperature side). (Kresse, 1983;Nagabhushan et al, 1988;Urban et al, 2000). Ratna et al (1980) have proposed the existence of two SmA phases on the basis of two different values of the activation barriers in 4-cyanophenylin-3 0 -methyl-4(4 0 -n-undecylbenzoyloxy)benzoate.…”

Section: Resultsmentioning

confidence: 97%

Dielectric relaxation studies in n-(4-octyloxy-2-hydroxybenzylidene)-4-carbethoxyaniline

Dhar¹,

Gupta

Agrawal

et al. 2004

Phase Transitions

View full text Add to dashboard Cite

Temperature dependent dielectric spectroscopy of a newly synthesized compound N-(4-octyloxy-2-hydroxybenzylidene)-4-carbethoxyaniline, having a wide temperature range ($70 C) Smectic A (SmA) phase has been carried out in the frequency range 100 Hz-10 MHz. Dielectric permittivity and loss in the homeotropic (" 0 k and " 00 k ) and planar (" 0 ? and " 00 ? ) alignments of the molecules have been determined. Relaxation frequencies corresponding to the rotation of the molecules about their short axes have been found to lie below 1 MHz and exhibit Arrhenius behaviour. Relaxation frequencies corresponding to the rotation of the molecules about their long axes are expected to lie above 10 MHz. Dielectric anisotropy (Á" 0 ¼ " 0 k À " 0 ? ) has been found to be negative throughout the range of the SmA phase.

show abstract

“…A second factor that must show appreciable change, as has indeed been seen experimentally for bulk systems [17][18][19]. In this paper we be kept in mind is that a calculation of the precise amount of sample inside the membrane is not trivial.…”

Section: Introductionmentioning

confidence: 91%

“…To phases. The magnitude of the decrease, a factor of 4, account for the d.c. conductivity (s) contribution to is quite large, but is typical for the bulk SmA-CrB the imaginary part of the dielectric constant, the term transition [17][18][19]. The inset of gure 5 (a) shows the Õ i(s/2pe o f )N was added to the right hand side of data for the two-phase region; the values in this region equation (1).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the two-dimensional melting transition of a liquid crystal confined in Anopore membranes

Sandhya¹,

Nair²,

Prasad³

et al. 2001

Liquid Crystals

Self Cite

View full text Add to dashboard Cite

show abstract

Dielectric studies of the hexatic B-smectic A and crystal B-smectic A transitions

Cited by 21 publications

References 9 publications

Study of dipole dynamics and pre-transitional effects at isotropic to nematic phase transition by low-frequency dielectric relaxation measurements

Study of dipole dynamics and pre-transitional effects at isotropic to nematic phase transition by low-frequency dielectric relaxation measurements

Dielectric relaxation studies in n-(4-octyloxy-2-hydroxybenzylidene)-4-carbethoxyaniline

Dynamics of the two-dimensional melting transition of a liquid crystal confined in Anopore membranes

Contact Info

Product

Resources

About