Optical light crossing

The crossed polarizer effects of both types are used in analysis work. The concentration of optically active organic materials is determined by the degree of rotation. In plastic processing the residual strains in molded materials as well as the degree of orientation of polymers is determined by the effect on polarized light. Crossed polarizers are used with special wave plates to control the amount of light that passes through an optical system. 

However, on a lightly cross-linked hydroxyethylmethacrylate/styrene polymer that swells in polar solvents (22, 365), or on a silica-gel support (366), catalyst performance matches that of the soluble one for the precursor amino acid substrates. A rhodium-DIOP analog has also been supported on a polymer containing pendent optically active alcohol sites [incidentally, formed via hydrosilylation and hydrolysis of a ketonic polymer component using an in situ rhodium(I)-DIOP catalyst]. The supported catalyst in alcohol again matched that of the soluble catalyst for... 

Fig. 4.2. Growing spherulites observed during the crystallization of PEO in an optical microscope (polarized light, crossed nicols)...

Fig. 4.7. Banded spherulites of PE. Optical micrographs showing a regular sequence of concentric rings (polarized light, crossed nicols left) and electron micrographs of a surface which cuts through a spherulite (obtained by Vaughan and Bassett [31] right)...

Figure 11. Optical micrograph of anisotropic dispersion o f PTFE whiskers (bottom layer of Figure 10), showing large ordered domains. Magnification lOOX, polarized light, crossed Nicols.

Chirality is usually seen optically in the form of rotation of the optical axis of a linearly polarized light crossing a chiral material (optical activity). In isotropic liquids optical activity requires chiral molecules, which results in typically of about 1 degree rotation of a light crossing 1 cm slab. In liquid crystals molecular chirality leads to helical structure, which enhances the optical activity so that the optical rotation (OR) can be as large as 100deg/p,m in some short pitch cholesteric or SmC materials. 

Like e, t is the product of two contributions the concentration N/V of the centers responsible for the effect and the contribution per particle to the attenuation. It may help us to become oriented with the latter to think of the scattering centers as opaque spheres of radius R. These project opaque cross sections of area ttR in the light path. The actual cross section is then multiplied by the scattering efficiency factor optical cross... 

Polypropylene molecules repeatedly fold upon themselves to form lamellae, the sizes of which ate a function of the crystallisa tion conditions. Higher degrees of order are obtained upon formation of crystalline aggregates, or spheruHtes. The presence of a central crystallisation nucleus from which the lamellae radiate is clearly evident in these stmctures. Observations using cross-polarized light illustrates the characteristic Maltese cross model (Fig. 2b). The optical and mechanical properties ate a function of the size and number of spheruHtes and can be modified by nucleating agents. Crystallinity can also be inferred from thermal analysis (28) and density measurements (29). 

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