Residual birefringence

Figure 1. Time dependence of the birefringence signal under the action of a reversing electric pulse of a PVC solution at C = 10 gcm and T = 25°C. The quenching concentration was 0.5 10 g cm". The single exponential curve (dotted line) deduced from the best fit of "Equation 8" to birefringence decay curve is indistinguishable from the experimental curve. Residues (i.e. difference between theoretical and experimental curve) are plotted below the birefringence curve.

Figure 2. Time dependence of the "birefringence decay signal, at the removal of the electric field, of a PVC solution at C = 10" g cm and for a quenching concentration of 1.6 10 g cm . Temperatures are T = 25°C (Fig,2a) and T = 60°C (Fig.2b). Dotted lines represent the single exponential curves deduced from the "best fit of Equation 8 to the experimental curves. Residues (i.e. difference between these two curves) are plotted below.

Transparency, gloss, color, refractive index, and reflectance are the properties normally associated with aesthetics of plastic materials. In some areas, changes in optical properties, increases in haze after abrasion testing (285), color differences after weathering, and birefringence analysis of residual stress within a transparent part (286) are all used to measure the effects of applied stresses. Measurements of color, gloss, refractive index, and haze apply to many products beyond plastics and use similar techniques. Reference should be made to this general topic for detailed information (see Color). 

For a typical chiral organic compound, such as 2-butanol, the circular birefringence, nL - wR, at A = 589 nm is of the order of 10-7. Even for a very high a = 40° mm-1 at A = 589 nm ( wL - nR 2 X 10 4), linear birefringence, which may arise from residual ordering/aggregation of polymer chains, could easily overwhelm the circular birefringence. 

The photoselection in azobenzene polymers (Figure 11) is rather a general phenomenon.77-84 Systematic studies have been conducted by Natansohn and coworkers on the photoinduced molecular reorientation of azobenzene units to induce birefringence and dichroism of thin films of acrylate amorphous polymers with Dispose Red (DR) pendant residues, which have been attracting extensive... 

The seven-residue peptide A -acetyl-Lys-Leu-Val-Phe-Phe-Ala-Glu-NH2 is shown by electron microscopy to form highly ordered fibrils upon incubation of aqueous solutions. X-ray powder diffraction and optical birefringence measurements have confirmed that these are amyloid fibrils. The peptide conformation and supramolecular organization in fibrils were investigated by solid state NMR. ... 

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