Dynamic light scattering, nematics

Berry, G.C. Static and Dynamic Light Scattering on Moderately Concentraded Solutions Isotropic Solutions of Flexible and Rodlike Chains and Nematic Solutions of Rodlike Chains. VoL 114, pp, 233-290. 

Using dynamic light-scattering measurements [Jamieson et al, 1996], Syi was determined for nematic solutions of a SCLCP, which had a weakly prolate or oblate conformation (i.e., R /R l), based on ER measurements of Sr]b and Srjc, and indicated [Liu et al, 1999] that Syi ckTtR/N, whereas the Brochard model predicts [via Eq. (1.95)] that Syi 0. 

Benmouna, F. Peng, B. Gapinski, J. Patkowski. A. Ruhe. J. Johannsmann, D. Dynamic light scattering from liquid crystal polymer brushes swollen in a nematic solvent. Liq. Cry St. 2001, 2S, 1353- 1360. 

The capillary condensation phenomenon is of course not exclusive to water. It can be found in any confined system, where the surfaces prefer one phase over another and there is a first order phase transition between the phases of the material between the surfaces. A nematic liquid crystal is an example of such a system exhibiting a first order phase transition between the isotropic and the nematic phase. For this system, the nematic capillary condensation has been predicted by P. Sheng in 1976 [17]. Since the isotropic-nematic phase transition is only weakly first order, the phenomenon is not easy to observe. One has to be able to control the distance between the surfaces with a nanometer precision and the temperature within 10 K, which is unachievable to methods like NMR, SEA, DSC, etc., and very difficnlt to achieve in dynamic light scattering experiments [18,19]... 

First detailed dynamic light scattering (DLS) experiments using bulk liquid crystal samples have confirmed the theoretically predicted existence of two dissipative fluctuation eigenmodes in the nematic liquid crystalline phase the first mode being a combination of splay and bend distortion and the second one a combination of twist and bend fluctuations [55,56]. Both modes are overdamped and the relaxation rate 1/r of each mode depends on the fluctuation wave vector q and viscoelastic properties of the sample [57] ... 

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