Photoconductive plastic

PVCB is brown in color, obtained by reacting acetylene with carbazole. The plastic has excellent electrical properties and good heat and chemical resistance. Use includes high frequency dielectrics, impregnant for paper capacitors, and photoconductive plastics. 

Numerous photoconductive plasticizers are used to lower the glass transition temperature to below 20°C and act as hole transporting plasticizers. " These include N-meth-ylcaibazole, N-ethylcaibazole, N-butylcarbazole, N-hexylcaibazole, N-phenylcarbazole,... 

On the other hand, the photoconductivity of a poly(vinyl chloride) copolymer and of sucrose benzoate each containing the leucobase of malachite green was characteristic of the dyestuff and independent of the polymeric host (137). This is similar to the behavior of conventional impurity semiconductors. However, a distinction must be drawn between an impurity which acts solely as an impurity providing an easier path to the conduction band, one which acts only as a plasticizer and one which may act as both impurity and plasticizer. 

In the photorefractive polymer composites described above, the value of the glass transition temperature is of great importance because it needs to be in a range where the electro-active chromophores can be reoriented by the photorefractive space-charge charge field. Adjustment of Tg is done though the addition of a plasticizer. Examples of plasticizers are shown in Fig. 23. As for the polymer matrixes, plasticizers can be photoconducting or inert. ECZ (molecule (a) in Fig. 23) is widely used with PVK. Inert plasticizers such as BBP (molecule (c) in Fig. 23) have also been combined with PVK [86]. 

Alkyl substituted anthracene has found application in plasticization of poly(N-vinyl carba-zole) residing in photoconductive layer of imaging member. 

The material has to simultaneously possess photoconductivity and electro-optical effect to have photorefractive properties. Typical candidate materials have low glass transition temperature, frequently reduced by the plasticizer. Diffraction efficiency is improved by addition of the plasticizer because chromophore groups have higher rotational mobility and increase their contribution of birefringence to the total refractive index modulation. ... 

Poly(N-vinyl carbazole), PVK, is a glassy polymer which easily fails by a cracking fracture. Plasticizers are needed to improve mechanical properties, reduce viscosity, and lower processing temperatnre. PVK is employed in photorefractive systems and as such it must possess photoconductivity and electro-optic effects. These ate related to the crystallization and the glass transition temperature. ... 

Selenium is involved in some important specialist uses [1], the largest being in the electronics and related industries. Its important use in xerography relates to the photoconductivity of the element. Its asymmetrical conductivity led to the development of surge-resistant rectifiers, while semiconductors, photoelectric cells, and infrared optic materials may all involve selenium. Other relatively major uses are in the manufacture of pink and ted glasses and for heat-resistant red pigments in plastics, enamels, paints, and inks (cadmium sulfoselenide). 

Progress in this area has been considerable in recent years and hopefully some non precious metal catalyst will be used in fuel cells in the near future. On the other hand, the stability of metallophthalocyanines makes them appropriate for applications in various fields such as chemical catalysis (such as the MEROX process for the sweetening of oils), dye stuffs, coloring for plastics and metal surfaces, sensors, chromatographic detectors, photoconducting agents, and so on. These complexes are also used for photobiology and photodynamic cancer therapy, electrochemical... 

A number of composite systems have been reported in which a polymer possessing one of the requisite functionalities, e.g., covalently attached NLO chromophores, is doped with the others, e.g., CG and CT dopants, or a photoconductive polymer, e.g., poly(N-vinylcarbazole), is doped with the sensitizer and NLO dopants (1, 4-7). The high dopant loading levels necessary (up to 50 wt%) result in severe limitations of doped systems, including diffusion, volatilization, and/or phase separation (crystallization) of the dopants. In addition, plasticizers and compatibilizers are often used to lower the glass transition temperature (Tg) of the polymer and increase solubility of the dopants in the host polymer, respectively. This, in turn, dilutes the effective concentration of CT, CG, and NLO moieties, diminishing the efficiency and sensitivity of the photorefractive polymer composite. 

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