Cross-polarized optical microscopy

Fig. 2.2 a Schematic illustration of smectic layer red plane) construction of a tori focal conic domain on randomly planar anchoring induced surface. The green rods represent liquid crystal molecules, b SEM image of array of tori focal conic domains and (c) its corresponding cross-polarized optical microscopy image... 

FIGURE 2.6 Comparison of cross-polarized optical microscopy pictures of unfilled polymers (fop) and their respective nanocomposites bottom) with 3 wt% of montmo-rillonite fillers PEO left), PP-g-MA middle), and sPS right). 

Methods used to compare and contrast the crystallization behavior of water soluble crystalline polymers with dispersed silicates may include cross-polarization optical microscopy (CPOM) or atomic force microscopy (AFM), depending upon physical properties of the materials such as spherulite size and optical properties. Other methods used to study crystallization behavior of such materials include differential scanning calorimetry (DSC) and x-ray diffraction (XRD). 

Cross-polarized optical microscopy and atomic force microscopy... 

The nucleation density as a function of silicate loading, as measured from cross polarization optical microscopy. Crystallization is done at 45°C (squares) and 50°C (circles). The number of nucleated spherulites per unit area Increases by more than tenfold, even at low silicate loadings. Copyright Chem. Mater. 2003,vol.15, pp. 844-849. 

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). 

Such an ordered structure is able to deflect polarized light, so if native starch granules are observed by means of polarized optical microscopy, Maltese crosses will be detected. 

Fig. 4 Structure and properties of nanocellulose, (a) Hierarchical assembly of cellulose molecules into cellulosic fibers. Adapted, with permission, from [131]. Copyright 2012 Elsevier, (b) Proposed mechanism of formation of CNF cross-linked with metal cations. Reproduced, with permission, from [132]. Copyright 2013 American Chtanical Society, (c) Effect of the type of metal cation on the frequency-dependent storage modulus of CNF hydrogels, probed by dynamic frequency sweeps (25 °C) at a strain rate of 0.5 %. Adapted, with permission, from [132]. Copyright 2013 American Chemical Society, (d) Polarization optical microscopy photograph of a biphasic 8.78 % (w/w) CNC suspension. Adapted, with permission, from [133]. Copyright 1996 American Chemical Society, (e) Polarization optical microscopy photograph of a CNC suspension. Scale bar. 200 pm. Reproduced, with permission, from [134]. Copyright 2000 Amaiean Chemical Society...

Cubic phases (Cub) are mesophases of cubic symmetry (Diele, 2002). Because of their high symmetry, their physical properties are no Imiger anisotropic. No defect texture is observed by polarizing optical microscopy (POM vide infra) and the image between crossed polarizers remains black. The cubic mesophases are very viscous and often their formation kinetics is very slow. Although cubic mesophases are very common for lyotropic LCs, where a cubic phase is possible between any pair of phases, there are only relatively few examples of cubic mesophases in thermotropic LCs. Whereas a cubic mesophase can be relatively easily detected when it is present between two anisotmpic mesophases, it is difficult to observe the formation of the cubic phase when it is formed by cooling an isotropic liquid. In this case, a deformatirMi of air bubbles in the melt is observed, as well as a sharp increase in the viscosity of the liquid. 

Cross-polarization confocal microscopy is a new 3D imaging method developed at ANL [9]. It combines two well-established optical methods, the cross-polarization backscatter detection and the scanning confocal microscopy, and can achieve 3D subsurface imaging with sub-micron spatial resolutions. A schematic diagram of the system is shown in Fig. 7. 

As well known, nanofillers often have significant influence on the crystal morphology of a semicrystalhne polymer. As shown in Figure 5.5, various spheruHte morphologies of PET and PET /clay nanocomposites have been characterized with polarized optical microscopy [21]. Neat PET demonstrates a well-defined spheruHte texture with a fibril pattern and a maltese cross at 200 °C. However, the maltese cross is not observed at higher crystallization temperature. PET/clay nanocomposites exhibited typical crystalline morphologies indicating that day exhibits a... 

In many cases unique optical textures are observed for the various orientations and structures of the three classes of liquid crystals. Thin films of nematic crystals, for example, can be identified by the pattern of dark threads (isogyres) which can appear in the optical microscope in transmission with crossed polarizers. Hot stage polarizing optical microscopy is often used to identify the phases and the transition temperatures. In some cases, the optical texture... 

Surface lateral patterns and cell density were studied by cross-polarized optical and fluorescent microscopy. These two different types of images were acquired sequentially over a grid of positions on each library by using a multi-... 

In situ observation of the polymerization process of /3-CF by polarization optical microscopy (POM), scanning electron microscopy (SEM), and TEM provided information on the molecular orientation within the spherulites of synthetic cellulose [43]. POM observations revealed that two types of spherulites were formed one displaying a well-defined Maltese cross identified... 

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