Light microscopy birefringence

Optical properties of fibers are measured by light microscopy methods. ASTM D276 describes the procedure for fiber identification using refractive indexes and birefringence. Other methods for determining fiber optical properties have been discussed (3,38—44). However, different methods of determining optical properties may give different results (42). 

Gout can be diagnosed by the presence of negatively birefringent monosodium urate crystals in aspirated synovial fluid examined by polarized-light microscopy. Here, crystals are within polymorphonuclear leukocytes. 

There are several techniques used to image the microstructure of fat crystal networks. (See Chapter 11 on Imaging. ) The most commonly used imaging method is polarized light microscopy (PLM) since fat crystals are birefringent and appear white, while the liquid oil is not and thus appears black. 

Ferrocene-containing liquid crystalline polymers 30 have been reported from the solution polymerization of l,T-bis(chlorocarbonyl)ferrocene, terephthaloyl chloride, and methylhydroquinone in refluxing dichloromethane [38], as indicated in Scheme 10-11. With one exception, these ferrocene containing copolyesters were reported to have birefringent melts. The presence of liquid crystallinity was verified by differential scanning calorimetry (DSC), polarized light microscopy, and X-ray diffraction studies. 

Figure 1.36 Resultant polarized light by vector addition of two plane-polarized light waves from a birefringent object, the ordinary (O) wave and extraordinary (E) wave. (Reproduced with permission from D.B. Murphy, Fundamentals of Light Microscopy and Electronic Imaging, Wiley-Liss. 2001 John Wiley Sons Inc.)...

Fig. 10 Microstructure of rotationally molded polypropylene samples (A) undercured specimen viewed under polarized light microscopy (B) overcured specimen viewed under polarized light microscopy and (C) overcured specimen viewed under fluorescence microscopy. In these pictures, the degraded layer shows higher birefringence. (From Ref.P. )...

Crosspolarized photomicrographs of PEO 1, EO-Is-EO 2, EO-Is-EO 3, and EO-Is-EO 4 films cast from 1% benzene solutions at 30° C are presented in Figure 1. The spherulitic texture with negative birefringence became less perfect and led to a less clear Maltese cross as the fraction of amorphous Is segment increased. When the EO fraction constituted less than 50%, the texture was not clearly resolved by light microscopy. 

Figure 5. Polarized light microscopy photomicrograph of wet mount of waterlogged wood from a prehistoric habitation site, 100 B.C.-lOO A.D., Japan. The hydrated wood shows differential degradation of cell types. Only a few isolated cells have retained birefringent cellulose.

Figure 15. Wet preparation of waterlogged Salix sp. wood from Somerset Levelsy 6000-year-old Sweet Track site, England. A. Light microscopy photomicrograph. The hydrated wood cells contain amorphous cell wall remnants that can be seen by comparison with Figure 15B. B. Polarized light microscopy photomicrograph. The birefringent primary wall-middle lamella complex can be seen in the hydrated wood cells.

The depolymerization of crystalline cellulose in wood has been observed with polarized light microscopy (IT). A loss of birefringence was associated with early stages of brown rot. The attack on cellulose is rapid and difiuse throughout the wood. The cells appear to maintain their usual form, but will shatter and collapse because they lack the strength that cellulose provides the woody cell wall (Figure 6b). 

Crystallinity in the freeze-dried product can normally be detected by polarized light microscopy, through the presence of birefringence in the sample [1]. Although microscopy is simple, quick, and sensitive to... 

Low- and high-powered microscopes are used to examine the morphological features of the fibres and the initial determination of whether the fibre is natural or man-made. FTIR microscopy can be used on a synthetic fibre to provide information in relation to the functional groups present this can be used to pinpoint which synthetic fibre it is. Polarising light microscopy is used with synthetic fibres plane-polarised Ught interacts with the fibres in order to provide refractive index values (many of these fibres have two refractive indices due to the chemical structure of the fibre and are said to be birefringent). This helps in the identification of the synthetic fibre. 

The polymer network structure can be studied by various means. Optical characterization is particularly versatile, since it can probe the composites directly and test whether, and to what degree, the network is oriented (75, 27, 30, 31), Hot-stage cross polarized light microscopy can be used to test the influence of monomer or polymer on LC phase transitions of these composites. Measurement of the birefringence of the bare polymer network, or of the LC composite in the isotropic state, yields information concerning anisotropy of the polymer network and of the type and strength of interaction between the network and LC matrix (75, 27, 30, 31). 

While spherulitic morphologies are the most widely observed forms of crystallization of linear-chain polymers, other equiaxed forms of growth of polyhedra referred to as hedrites were also reported. These less regular forms of several types of polymers showing similar birefringence in light microscopy were discussed by Geil (1958). 

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