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Magnetic Resonance Studies of Thermotropic Liquid Crystals

1973; Volume: 21; Issue: 1-2 Linguagem: Inglês

10.1080/15421407308083316

0026-8941

G. R. Luckhurst,

Nonlinear Dynamics and Pattern Formation

Abstract It is relevant to begin this review by asking why it should be devoted to a technique for investigating the properties of liquid crystals rather than the properties themselves. There are a variety of responses to such a question. For example magnetic resonance spectroscopy, unlike many techniques, is able to provide information at the molecular level because the step from a spectrum to a molecular property can usually be taken with complete certainty. Secondly, the technique may be employed to probe both the static and dynamic properties of the system although we shall only be concerned with the static properties. Finally, this branch of spectroscopy may be employed to study a wide range of problems. As an indication of this versatility consider the following aspects of liquid crystals which have been investigated by magnetic resonance: the orientational order in cholesteric, nematic and smectic mesophases; anisotropic solute-solvent interactions in liquid-crystalline solutions; the material constants in continuum theory, the perturbation of the director by several constraints; magnetohydrodynamics in the nematic mesophase; the magnitude and dynamics of thermal fluctuations; the rate and nature of molecular reorientation with respect to the director. It is clearly impossible to describe all of these examples of the applications of magnetic resonance spectroscopy in detail. Instead we shall attempt to concentrate on the physics of just a few applications in order to illustrate the power and potential of the technique in studying liquid crystals.