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Polyvinylcarbazole
Polyvinylcarbazole (PVK) is a temperature-resistantHans-Dieter Jakubke, Ruth Karcher (Koordinatoren): ''Lexikon der Chemie'' in drei Bänden, Spektrum Verlag, Band 3, Heidelberg 1999, , S. 92. thermoplastic polymer produced by radical polymerization from the monomer ''N''-vinylcarbazole. It is a photoconductive polymer and thus the basis for photorefractive polymers and organic light-emitting diodes.. History Polyvinylcarbazole was discovered by the chemists Walter Reppe (1892-1969), Ernst Keyssner and Eugen Dorrer and patented by I.G. Farben in the USA in 1937.US-Patent Nr. 2,072,46pdfpiw.uspto.gov ''Production of polymeric N-Vinyl compounds.'' Priorität 24. Juli 1934, veröffentlicht am 2. März 1937, Anmelder: I.G. Farbenindustrie Aktiengesellschaft, Erfinder: Walter Reppe, Ernst Keyssner, Eugen Dorrer. PVK was the first polymer whose photoconductivity was known. Starting in the 1960s, further polymers of this kind were sought. Production Polyvinylcarbazole is obtain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Light-emitting Diodes
An organic light-emitting diode (OLED), also known as organic electroluminescent (organic EL) diode, is a type of light-emitting diode (LED) in which the emissive electroluminescent layer is an organic compound film that emits light in response to an electric current. This organic layer is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, and portable systems such as smartphones and handheld game consoles. A major area of research is the development of white OLED devices for use in solid-state lighting applications. There are two main families of OLED: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. An OLED display can be driven with a passive-matrix (PMOLED) or active-matrix (AMOLED) control ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical Polymerization
In polymer chemistry, radical polymerization (RP) is a method of polymerization by which a polymer forms by the successive addition of a radical to building blocks ( repeat units). Radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules. Following its generation, the initiating radical adds (nonradical) monomer units, thereby growing the polymer chain. Radical polymerization is a key synthesis route for obtaining a wide variety of different polymers and materials composites. The relatively non-specific nature of radical chemical interactions makes this one of the most versatile forms of polymerization available and allows facile reactions of polymeric radical chain ends and other chemicals or substrates. In 2001, 40 billion of the 110 billion pounds of polymers produced in the United States were produced by radical polymerization. Radical polymerization is a type of chain polymerization, along with anionic, cationic and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoconductor
Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation. When light is absorbed by a material such as a semiconductor, the number of free electrons and holes increases, resulting in increased electrical conductivity. To cause excitation, the light that strikes the semiconductor must have enough energy to raise electrons across the band gap, or to excite the impurities within the band gap. When a bias voltage and a load resistor are used in series with the semiconductor, a voltage drop across the load resistors can be measured when the change in electrical conductivity of the material varies the current through the circuit. Classic examples of photoconductive materials include: * photographic film: Kodachrome, Fujifilm, Agfachrome, Ilford, ''etc.'', based on silver sulfide and silver bromide. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoplastics
A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate by intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. In this state, thermoplastics may be reshaped, and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion. Thermoplastics differ from thermosetting polymers (or "thermosets"), which form irreversible chemical bonds during the curing process. Thermosets do not melt when heated, but typically decompose and do not reform upon cooling. Above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not full ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Photorefractive Materials
Organic photorefractive materials are materials that exhibit a temporary change in refractive index when exposed to light. The changing refractive index causes light to change speed throughout the material and produce light and dark regions in the crystal. The buildup can be controlled to produce holographic images for use in biomedical scans and optical computing. The ease with which the chemical composition can be changed in organic materials makes the photorefractive effect more controllable. History Although the physics behind the photorefractive effect were known for quite a while, the effect was first observed in 1967 in Lithium niobate, LiNbO3. For more than thirty years, the effect was observed and studied exclusively in inorganic materials, until 1990, when a nonlinear organic crystal 2-(cyclooctylamino)-5-nitropyridine (COANP) doped with 7,7,8,8-tetracyanoquinodimethane (Tetracyanoquinodimethane, TCNQ) exhibited the photorefractive effect. Even though inorganic material ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Styrene
Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concentrations have a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers, and is typically made from benzene for this purpose. Approximately 25 million tonnes of styrene were produced in 2010, increasing to around 35 million tonnes by 2018. Natural occurrence Styrene is named after storax balsam (often commercially sold as ''styrax''), the resin of Liquidambar trees of the Altingiaceae plant family. Styrene occurs naturally in small quantities in some plants and foods (cinnamon, coffee beans, balsam tree (other), balsam trees and peanuts) and is also found in coal tar. History In 1839, the German apothecary Eduard Simon isolated a volatile liquid from t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CeBIT 2011 Samstag PD 116
CeBIT was a computer expo which, at its peak, was the largest and most internationally representative. The trade fair was held each year on the Hanover fairground, the world's largest fairground, in Hanover, Germany. In its day, it was considered a barometer of current trends and a measure of the state of the art in information technology. It was organized by Deutsche Messe AG. With an exhibition area of roughly and a peak attendance of 850,000 visitors during the dot-com boom, it was larger both in area and attendance than its Asian counterpart COMPUTEX and its no-longer held American equivalent COMDEX. CeBIT is a German language acronym for ''Centrum für Büroautomation, Informationstechnologie und Telekommunikation'', which translates as "Center for Office Automation, Information Technology and Telecommunication". The final CeBIT took place in 2018. History CeBIT was traditionally the computing part of the Hanover Fair, a big industry trade show held every year. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' are methyl), with the formula . Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, ''e.g.'', testosterone, and the solvent acetone. Nomenclature and etymology The word ''ketone'' is derived from ''Aketon'', an old German word for ''acetone''. According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix ''-ane'' of the parent alkane to ''-anone''. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names, although some introdu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halogenated Hydrocarbons
The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents of hydrogen atom. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes that contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aromatic Hydrocarbon
Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated." The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were understood. The current definition of aromatic compounds does not have any relation to their odor. Aromatic compounds are now defined as cyclic compounds satisfying Hückel's rule. Aromatic compounds have the following general properties: * Typically unreactive * Often non polar and hydrophobic * High carbon-hydrogen ratio * Burn with a strong sooty yellow flame, due to high C:H ratio * Undergo electrophilic substitution reactions and nucleophilic aromatic substitutions Arenes are typically split into two categories - benzoids, that contain a benzene derivative and follow the benzene ring model, and non-benzoids that contain other aromatic cyclic derivatives. Aromatic compounds are commonly used in organic synthesis and are involved in m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoprene
Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. It is produced by many plants and animals (including humans) and its polymers are the main component of natural rubber. History and etymology Charles Greville Williams, C. G. Williams named the compound in 1860 after obtaining it from the pyrolysis of natural rubber. He correctly deduced the mass shares of carbon and hydrogen (but arrived at an incorrect formula C10H8 because the modern atomic weight of carbon was not adopted until the Karlsruhe Congress held later that year). He did not specify the reasons for the name, but it is hypothesized that it came from "propylene" with which isoprene shares some physical and chemical properties. The first one to observe recombination of isoprene into rubber-like substance was in 1879, and William A. Tilden identified its structure five years later. Natural occurrences Is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
