scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Phenomenology of short-range-order effects in the isotropic phase of nematic materials

15 Dec 1969-Physics Letters A (North-Holland)-Vol. 30, Iss: 8, pp 454-455
TL;DR: In this article, the magnetic birefringence, the intensity and the width in frequency of the Rayleigh scattering, and the flow bireringence are discussed in terms of a small number of phenomenological parameters.
About: This article is published in Physics Letters A.The article was published on 1969-12-15. It has received 301 citations till now. The article focuses on the topics: Flow birefringence & Birefringence.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, the physical properties of nematic, cholesteric, and smectic liquid crystals are discussed and a wide variety of phenomena in liquid crystals, including elastic distortions, disclinations, flow properties, fluctuations, light scattering, wave propagation, nuclear magnetic resonance, effects of magnetic and electric fields, electrohydrodynamics, and optical properties.
Abstract: This review discusses the physical properties of nematic, cholesteric, and smectic liquid crystals. Molecular theories of the liquid crystal phases are discussed and the molecular field theories of the phase transitions between the various liquid crystal phases are presented. The elastic theory and hydrodynamics of liquid crystals is developed. A wide variety of phenomena in liquid crystals, including elastic distortions, disclinations, flow properties, fluctuations, light scattering, wave propagation, nuclear magnetic resonance, effects of magnetic and electric fields, electrohydrodynamics, and optical properties, is discussed.

978 citations

Journal ArticleDOI
TL;DR: In this article, the authors assume that the local state of order in the isotropic phase is a symmetric traceless tensor Qαβ, proportional to the anisotropic part of a tensor property such as the magnetic susceptibility.
Abstract: We assume that (1) the local state of order in the isotropic phase is a symmetric traceless tensor Qαβ, proportional to the anisotropic part of a tensor property such as the magnetic susceptibility; (2) the free energy may be expanded in powers of Qαβ and of its gradients. This allows a unified description covering the anomalous magnetic birefringence, the intensity of light scattering, and the properties of the nematic/isotropic interface. For a cholesteric, although the optical rotation is huge in the ordered phase, we predict that it should not be anomalous just above the transition point Tc. We also investigate the dynamics of fluctuations of Qαβ, and discuss the flow birefringence, the frequency width of the Rayleigh scattering, and the attenuation of ultrasonic shear waves, in terms of 3 viscosity coefficients.

766 citations

Journal ArticleDOI
Ivan Haller1

498 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the statistical interdependence of the faster rotational reorientation of the individual spinbearing molecules and the (slower) director or order-parameter fluctuations.
Abstract: The theory of spin relaxation for liquid crystals is examined with the objective of properly analyzing the statistical interdependence of the faster rotational reorientation of the individual spin‐bearing molecules and the (slower) director or order‐parameter fluctuations. The analysis is presented in terms of a composite Markov process including both types of motions. It is shown that one recovers a sum of spectral‐density terms which, in lowest order in fluctuations, correspond to (1) reorientation of the molecule relative to the equilibrium potential of mean torque, (2) effects of director fluctuations, and (3) a negative cross‐term between these two processes which bears a simple relation to (2). Detailed results are given for the particular models of director fluctuations in the nematic phase, quasicritical order fluctuations on either side of the isotropic–nematic phase transition, and slow fluctuations in the local structure. Effects of localized cooperative modes of molecular reorientation are als...

320 citations

Journal ArticleDOI
TL;DR: A review of the wide variety of predictions that results from a Landau-type of description of the nematic-isotropic phase transition is given in this paper, which includes a discussion of the nature of the order parameter and of the various types of possible phases.

291 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors estimate the contributions to T1 and T2 in a nematic liquid crystal arising from the fluctuations in the orientational order, which results in relaxation times of the order of one second which is typical of ordinary liquids.

263 citations

Journal ArticleDOI
TL;DR: Using a light-beat laser spectrometer, the authors observed the relaxation of the thermally excited fluctuations of anisotropy in the nematic phase of $p\ensuremath{-}\mathrm{azoxyanisole}$.
Abstract: Using a light-beat laser spectrometer, we observe the relaxation of the thermally excited fluctuations of anisotropy in the nematic phase of $p\ensuremath{-}\mathrm{azoxyanisole}$. We identify the two low-frequency purely dissipative modes recently predicted. A first study of the angular dependence of the width of these modes allows a determination of three among the six viscosity coefficients introduced by Leslie.

109 citations