Compound optical anisotropy

The optical anisotropies y and molar Kerr constants mK of model compounds, and of polylp-chlorostyrene) and polyfp-bromostyrene), are determined. Averages and over all conformations of the polymer chains are calculated as functions of the fraction wm of the meso diads using the RIS model originally developed for PS. 

It is evident that due to polymeric specificity of LC polymers most of the information on their molecular parameters, i.e. molecular mass, conformational state, polymeric chain flexibility and mobility, optical anisotropy and others, may be obtained from studies of dilute solutions of these compounds. However, taking into account that this branch of polymer science has already been reviewed 134>172-176> we will here confine our treatment only to the initial steps of LC phase formation in polymer solutions. 

TABLE 1. Phase transition temperatures for perfluorooalloyloxy compounds and corresponding optical anisotropy (An) and dielectric anisotropy (As). 

For a more definitive test of the theory, Irvine has determined the optical anisotropies of nematogens and analogous compounds from depolarized Rayleigh... 

Liquid-crystalline phases with two-dimensional order (Table 1) influence photochromic processes because their molecular orientation is reversibly altered by photochromic reactions owing to the marked structural changes of the photoactive molecules.3 Intensive interest has been focused on the photoinduced alteration of mesophases admixed with photochromic compounds, since photochromism can be transformed to the reversible modification of the optical anisotropy of liquid-crystalline states. This phenomenon is applicable to optical storage of information as nondestructive readout can be performed with light of wavelengths far from those causing the photochromic reactions. 

Figure 2.9. Optical anisotropy induced by the light in a film of the compound Alizarin Yellow GG-PEI kinetics of the parallel (dashed black line) and orthogonal (solid gray line) polarization components of the transmitted probe beam, (a) Induction and relaxation, solid black line presents two-exponential decay fit to the data, and (b) switching by alternation of polarization of the irradiating beam. Source Kulikovska et al., 2007. Reproduced with permission from American Chemical Society.

Furuya, H., Okamoto, S., Abe, A., Petekidis, G., and Fytas, G., Dipole moment and optical anisotropy studies of mesogenic twin compounds, a,< -bis[(4,4 -cyanobiphenyl)oxy]alkanes, 7. Phys. Chem., 99, 6483-6486 (1995). 

Based on comparisons with low molecular weight compounds, the optical clarity and the weak inner ring suggest that the organization is isotropic. However, nematic order was assigned to the polymer based on observation of optical anisotropy (10). The sharp line of medium intensity within the outer halo suggests some parallel packing of the side chains. 

Bordeau, M., Clement, C., Structural Study on Organosilicon Compounds by Depolarized Rayleigh Scattering. Determination of the Sign of Optical Anisotropies of Bonds and Groups with or without Silicon in the Aliphatic and Benzenic Series, J. Organometal. Chem. 202 [1980] 137/48. 

The aim of this article is to show that the new quasi-two-dimensional organic conductor p -(BEDO-TTF)5[CsHg(SCN)4]2 [hereafter called (BEDO)CsHg] (BEDO-TTF - bis-(ethylenedioxy)tetrathiafulvalene) which contains closed and open orbits displays rather complicated oscillatory spectra associated with magnetic breakdown (MB) and quantum interference (QI) effects. Tight binding band structure calculations for this compound are proposed to characterise its Fermi surface. The aim of the article includes also an investigation of the optical conductivity anisotropy with polarized infrared reflectance spectra. 

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