Isotropic light scattering

Vuks, Lisnyanskij and Shurupova ( 19 Vol. II, p. 79) have observed maxima of the isotropic light scattering in water propanol-mixtures. They found sharp maxima at x2 =0.15 (22 °C). 

Guillot NC, Le Duff Y, Rachet F, Chrysos M (2002) Anisotropic and isotropic light scattering in gaseous low-temperature helium. Phys Rev A 66 012505... 

Quadrupolar molecules. In a liquid composed of anisotropic non-polar molecules, the molar constant (291b) is still applicable in a first approximation (it defines the contribution from fluctuations in number density of the molecules, as in isotropic light scattering. The anisotropic molar constant (292) reduces to the contribution ... 

Figure 2.9 Flowchart of empirical calculation of isotropic light scattering losses in amorphous polymers.

Table 2.3 shows the calculated and observed values of the isothermal compressibility, refractive index, and isotropic light scattering of PMMA and PSt. The calculated values for both polymers show good agreement with the measured values. 

Table 2.3 Isotropic light scattering in PMMA and PSt at 633 nm. Comparison of calculations from their molecular structures with measurements.

Scattering losses in polymers arise from microscopic variations in the material density. By using Einstein s fluctuation theory, the intensity of the isotropic light scattering Vy° from thermally induced density fluctuations in a stmctureless liquid is expressed by ... 

Note that this also involves the assumption of isotropic molecules, which have the same polarizability in all directions. Unpolarized light consists of equal amounts of vertical and horizontal polarization, so the fraction of light scattered in the unpolarized (subscript u) case is given by... 

Liquid crystalline solutions as such have not yet found any commercial uses, but highly orientated liquid crystal polymer films are used to store information. The liquid crystal melt is held between two conductive glass plates and the side chains are oriented by an electric field to produce a transparent film. The electric field is turned off and the information inscribed on to the film using a laser. The laser has the effect of heating selected areas of the film above the nematic-isotropic transition temperature. These areas thus become isotropic and scatter light when the film is viewed. Such images remain stable below the glass transition temperature of the polymer. 

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. 

Perrin, F., 1942. Polarization of light scattered by isotropic opalescent media, J. Chem. Phys., 10, 415-427. 

The rotational diffusion coefficient Dr of a rodlike polymer in isotropic solutions can be measured by electric, flow, and magnetic birefringence, dynamic light scattering, and dielectric dispersion. However, if the polymer has some flexibility, its internal motion makes it difficult to extract Dr for the end-over-end rotation of the chain from data of these measurements. In other words, Dr can be measured only for nearly rodlike polymers. 

Data of Dr were obtained for low molecular weight poly (y-benzyl-L-gluta-mate) (PBLG) samples in isotropic solutions by two methods. Mori et al. [129] used dynamic electric birefringence, while Zero and Pecora [130] and Kubota and Chu [131] applied depolarized dynamic light scattering. Figure 18 shows... 

Fig. 27a, b. Comparison of Eq. (50) with the Dr data for isotropic solutions of relatively short PBLG samples in the plot of Dr/Dr0 vs X a data from dynamic electric birefringence by Mori et al. [129] (the same data as shown in Fig. 18) b data from dynamic light scattering by Kubota and Chu [131] and Zero and Pecora [130], The solid curve, theoretical values predicted by Eq. (50)... 

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