TRANSMISSION OPTICAL MICROSCOPY

It is optically transparent. This makes possible to do transmission optical microscopy to explore internal processes, such as the creation of brittle fractures. 

Shown in Fig. 2.8 (a) and (b) are example microphotos of the two-phase structure for two analogous materials based on PTHF of molar mass 2 000 g/mol and chain extended with BDO. They differ only in the type of diisocyanate, the rigid MDI or DBDI displaying a variable geometry. Transmission optical microscopy standard method was used to investigate the microstructures. 

Figure 5. Conducting pattern of poly(lb) generated by electrochemically induced pattern transfer (ECIPT) via explication of 0.9 Vfor 0.1 sec using O.l M TBAP/ACN electrolyte solution. Potential is referenced vs. Ag/Ag. As observed by transmission optical microscopy, oremge lines are lines of reduced poly(lb), black lines are gold leads located under the polymer film, and colorless regions consist of the precursor polymer, poly(la).

The process starts with the preparation of polymer solutions, for instance, polyvinyl alcohol (PVA), and metal compounds, for instance, 3d-metal chlorides. Afterwards, the solutions with a certain concentration are mixed in the ratio PVA-metal chloride equals to 20 1-1 5 (better 5 1). Then the prepared solutions are dried till they obtain gel-like colored films with further temperature elevation up to 100°C. The films obtained are controlled by spectral photometry, and also with help of transmission optical microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. When the film color changes to black, the films are heated in the furnace according to the following program 100-200-300-400°C. As a result, the dark porous semiproduct with many microcracks is formed, that is milled in spherical or jet mill. The nanopowder obtained is steamed and dispersed in hot water. After filtration, the powder is dried and tested with the help of Raman spectroscopy. X-ray photoelectron spectroscopy, transmission electron microscopy and electron microdiffraction. 

The examination of specimens in transmission necessarily requires that they be thin. Thus, the techniques of transmission optical microscopy are inappropriate for the examination of bulk specimens, or materials such as metals or conducting polymers which absorb strongly at visible wavelengths. Nevertheless, examination of such samples in reflection may provide useful structural information, through the observation of topographical features. 

Transmission optical microscopy revealed another toughening mechanism (see Figure 2.19). The image, taken under crossed polarized light, clearly shows... 

The common contrast modes include polarized light, phase contrast, differential interference contrast, and Hoffman modulation contrast [5]. Depending on the nature of the polymer, such as refraction index, sample thickness, and optical anisotropies in the materials, different modes of transmission optical microscopy can be employed by mounting special accessories in a classic optical microscope to overcome different problems. For example, a polarizer and analyzer can be mounted before and after the sample to construct a polarized light microscope, commonly used for semicrystalline polymers a phase plate and phase ring can be added to construct a phase contrast optical microscopy, which is common for studying a noncrystafline multiphase polymer system. 

For transmission optical microscopy (TOM) investigations, thin sections (c.a. 40 pm) of the mid-section of the DN-4PB crack tip damage zone were obtained by sectioning and polishing. These thin sections were then examined using an Olympus BX60 optical microscope under bright field. 

---