Pretransitional light scattering

Solids are characterized by a nonzero static shear elastic constant, whereas a liquid will not support static shear. Conventional viscometric techniques (i.e., capillary flow and falling balls), which now seem rather crude considering the fragile nature of the blue phase lattice, initially showed a large viscosity peak at the helical-isotropic transition [89], [90], [91]. Viscosities and other transport coefficients associated with the pretransitional region of the isotropic phase were addressed by light scattering [92], [93], [94], [95]. 

Light scattering is a probe of molecular motions, and may be used effectively to study pretransitional phenomena. Stintson et al. [123] studied light scattered by order parameter fluctuations in MBBA. Their data follow the relationship ... 

There are other reports on the study of pretransitional dynamics in polymeric and lyotropic nematics. Quantitative measurements of ratios of Frank elastic constants and Leslie viscosities in the pretransitional range of poly-y-benzyl-glutamate polymeric nematic are reported by Taratuta et al. [85]. McClymer and Keyes [86-88] report light scattering studies of pretransitional dynamics of potassium laurate-decanol-D20 system. An interesting study of a magnetic-field induced I N phase transition in a colloidal suspension is reported by Tang and Fraden [89]. 

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