NationMaster - Encyclopedia: Conductive polymer

A conductive polymer is an organic polymer semiconductor, or an organic semiconductor. Roughly, there are two classes-- the Charge transfer complexes and the conductive polyacetylenes. The latter include polyacetylene itself as well as polypyrrole, polyaniline, and their derivatives. Benzene An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and elementary carbon. ... Polymer is a term used to describe a very long molecule consisting of structural units and repeating units connected by covalent chemical bonds. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... An organic semiconductor is an organic compound that exhibits similar properties to inorganic semiconductors, specifically the presence of a hole and electron conduction layer and a band gap. ... A charge transfer complex is defined over a pair of a molecular groups, where one is electron donating and the other is electron accepting, where there is a partial transfer of electronic charge from the acceptor to the donor in an excited molecular state(excited state). ...

Most commercially produced organic polymers are electrical insulators. Conductive polymers, which are almost always organic, may have extended delocalized bonds (often composed of aromatic units) that create a band structure similar to silicon, but with localized states. When charge carriers (from the addition or removal of electrons) are introduced into the conduction or valence bands (see below) the electrical conductivity increases dramatically. Technically almost all known conductive polymers are semiconductors due to the band structure, however so-called zero band gap conductive polymers may behave like metals. The most notable difference between conductive polymers and inorganic semiconductors is the mobility, which until very recently was dramatically lower in conductive polymers than their inorganic counterparts, though recent advancements in self assembly are closing that gap. Benzene An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and elementary carbon. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ... Insulators are materials which prevent the flow of heat (thermal insulators) or electric charge (electrical insulators). ... Benzene An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and elementary carbon. ... A chemically conjugated system is a system of atoms covalently bonded with alternating single and double bonds (e. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... Electrical conductivity is a measure of a materials ability to conduct an electric current. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ... Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary. ... A semiconductor is a material that is an insulator at very low temperature, but which has a sizable electrical conductivity at room temperature. ... In physics, electron mobility (or simply, mobility), is used to describe the relation between drift velocity of electrons or holes in a solid material or electrons/ions in a gas, and an applied electric field. ... Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ... Self-assembly is the fundamental principle which generates structural organization on all scales from molecules to galaxies. ...

Delocalization can be accomplished by forming a conjugated backbone of continuous overlapping orbitals, for example, alternating single and double carbon-carbon bonds, which leaves a continuous path of overlapping p orbitals. In polyacetylene, but not in most other conductive polymers, this continuous string of orbitals creates degeneracy in the frontier molecular orbitals (the highest occupied and lowest unoccupied orbitals named HOMO and LUMO respectively) which leads to the filled (electron containing) and unfilled bands (valence and conduction bands respectively) that define a semiconductor. A chemically conjugated system, is a system of atoms covalently bonded with alternating single and double bonds (e. ... Electron atomic and molecular orbitals In quantum chemistry (electronic structure theory), the molecular electronic states, i. ... A chemical bond is the physical phenomenon of chemical substances being held together by attraction of atoms to each other through sharing, as well as exchanging, of electrons or electrostatic forces. ... Electron configuration is the arrangement of electrons in an atom, molecule or other body. ... Polyacetylene (PA) is conducting polymer of the rigid-rod polymer host family. ... In mathematics, a degenerate case is a limiting case in which a class of object changes its nature so as to belong to another, usually simpler, class. ... Electron atomic and molecular orbitals In quantum chemistry (electronic structure theory), the molecular electronic states, i. ... HOMO and LUMO are acronyms for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ...

However, conductive polymers generally exhibit very low conductivities. In fact, conduction in such relatively disordered materials is mostly a function of "mobility gaps" with phonon-assisted hopping, polaron-assisted tunnelling, etc. between localized states and not band gaps as in crystalline semiconductors. In solid-state physics, a polaron is formed when a moving charge (typically an electron or a hole) in a crystal with some ionic character polarizes (by its electric field) the lattice around it. ... Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

It is not until an electron is removed from the valence band (p-doping) or added to the conduction band (n-doping, which is far less common) does a conducting polymer become highly conductive. Doping (p or n) generates charge carriers which move in an electric field. Positive charges (holes) and negative charges (electrons) move to opposite electrodes. This movement of charge is what is actually responsible for electrical conductivity. A P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case positive) charges. ... An N-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case negative) charge carriers. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ... Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...

Following up an earlier paper defining conduction mechanisms in such polymers, McGinness, Corry, and Proctor reported a high conductivity state in an oxidized polyacetylene (melanin) and the first organic electronic device. This was a voltage-controlled switch (Science, vol 183, 853-855 (1974)). Their original "gadget" is now in the Smithsonian's collection of early electronic devices. This device also exhibited negative differential resistance, now a well-characterized hallmark of electronically-active organic materials. Polyacetylene (PA) is conducting polymer of the rigid-rod polymer host family. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ...

Though in a major journal and well-known at the time, this work was "lost" and went generally-uncited. Though their compound was also easily prepared by oxidizing DOPA, perhaps the use of "human melanoma tumour obtained at autopsy" as a source of melanin made other researchers reluctant to continue the work. The 2000 chemistry Nobel prize was awarded to others for the later discovery and characterization of passive high conductivity in other polyacetylenes. This prize also slighted the much earlier discovery of highly-conductive organic Charge transfer complexes, some of which are even superconductive. This may have been because most device applications involve conductive polyacetylenes. This is a list of Nobel Prize laureates in Chemistry from 1901 to the present day. ... A charge transfer complex is defined over a pair of a molecular groups, where one is electron donating and the other is electron accepting, where there is a partial transfer of electronic charge from the acceptor to the donor in an excited molecular state(excited state). ...

1 Chemistry
2 Physics
3 Applications
4 See also

Chemistry

Common classes of organic conductive polymers include poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(aniline)s, poly(fluorene)s, polynaphthalenes, poly(p-phenylene sulfide), and poly(para-phenylene vinylene)s. Classically, these compounds are known as polyacetylene, polyaniline, etc. "blacks" or "melanins". The melanin pigment in animals is generally a mixed copolymer of polyacetylene, polypyrrole, and polyaniline. Polyacetylene (PA) is conducting polymer of the rigid-rod polymer host family. ... A Polypyrrole (PPy) is a chemical compound formed from a number of connected pyrrole ring structures. ... Polythiophenes (PTs) are sulfur heterocycle polymers of thiophene which can become conducting when electrons are added or removed from the conjugated Ï€-orbitals via doping. ... Polyaniline (PANI) is a conducting polymer of the semi-flexible rod polymer family. ... Poly(p-phenylene sulfide) (PPS) is a conducting polymer of the semi-flexible rod polymer family. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ...

Doping

In silicon semiconductors, a few of the silicon atoms are replaced by electron rich (e.g., phosphorus) or electron-poor (e.g. boron) atoms to create n-type and p-type semiconductors, respectively. In contrast, there are two primary methods of doping a conductive polymer, both through an oxidation-reduction (redox) process. The first method, chemical doping, involves exposing a polymer, such as melanin (typically a thin film), to an oxidant (typically iodine or bromine) or reductant (far less common, but typically involves alkali metals). The second is electrochemical doping in which a polymer-coated, working electrode is suspended in an electrolyte solution in which the polymer is insoluble along with separate counter and reference electrodes. An electric potential difference is created between the electrodes which causes a charge (and the appropriate counter ion from the electrolyte) to enter the polymer in the form of electron addition (n doping) or removal (p doping). This article is about the chemical element. ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... An N-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case negative) charge carriers. ... A P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case positive) charges. ... Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ... Thin films are material layers of about 1 Âµm thickness. ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... General Name, Symbol, Number iodine, I, 53 Chemical series halogens Group, Period, Block 17, 5, p Appearance violet-dark gray, lustrous Atomic mass 126. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ... A reducing agent is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... The alkali metals are a chemical series. ... Electrochemistry is the study of the electronic and electrical aspects of chemical reactions. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... Insoluble Not soluble ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ... // An ion is an atom or a group of atoms (a chemical substance), or subatomic particle, with a net electric charge. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ...

The reason n doping is so much less common is that Earth's atmosphere is oxygen-rich, which creates an oxidizing environment. An electron-rich n doped polymer will react immediately with elemental oxygen to de-dope (re-oxidize to the neutral state) the polymer. Thus, chemical n doping has to be done in an environment of inert gas (e.g., argon). Electrochemical n doping is far less common in research, because it is much more difficult to exclude oxygen from a solvent in a sealed flask; therefore, although very useful, there are likely to be no commercialized n doped conductive polymers. Layers of Atmosphere (NOAA) Air redirects here. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... In English, to be inert is to be in a state of doing little or nothing. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... Look up flask in Wiktionary, the free dictionary. ...

Conjugation

The extended conjugation of a conductive polymer tends to give rise to fluorescence which has led to the rapid development of polymer-based light emitting devices (OLEDs) and organic photovoltaic devices. A chemically conjugated system, is a system of atoms covalently bonded with alternating single and double bonds (e. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... It has been suggested that PHOLED be merged into this article or section. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ...

Properties

The biggest advantage of conductive polymers is their processibility. Conductive polymers are also plastics (which are organic polymers) and therefore can combine the mechanical properties (flexibility, toughness, malleability elasticity, etc.) of plastics with the high electrical conductivities of a doped conjugated polymer. The term plastics covers a range of synthetic or semi-synthetic organic condensation or polymerization products that can be molded or extruded into objects or films or fibers. ... Elasticity has meanings in two different fields: In physics and mechanical engineering, the theory of elasticity describes how a solid object moves and deforms in response to external stress. ...

Physics

This increase in conductivity can also be accomplished in a field effect transistor (organic FET or OFET), or by irradiation. Strong coupling can also occur between electrons and phonons (mechanical oscillations such as heat vibrations, particles of sound) since both are constrained to travel along the polymer backbone. Large power N-channel field effect transistor The field-effect transistor (FET) is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel in a semiconductor material. ... An Organic Field-Effect Transistor (OFET) is a class of thin film transistors based on organic semiconductors. ... Photoconductivity is an optical and electrical phenomenon in which a material becomes more conductive due to the absorption of electro-magnetic radiation such as visible light, ultraviolet light, or gamma radiation. ... Generally, coupling means a mechanical connection between two things. ... A phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the atomic lattice of a solid. ...

Applications

In some cases, light emission is observed when a voltage is applied to a thin layer of a conductive organic polymer film. It has led to the development of flat panel displays using OLEDs, solar panels and optical amplifiers. This page is a list of sources of light. ... International danger high voltage symbol. ... Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays using cathode ray tubes, usually less than 10 cm (4 inches) thick. ... It has been suggested that PHOLED be merged into this article or section. ... Solar Panel (photovoltaic array) A Solar panel is a flat collection of solar cells or solar thermal collectors used for converting solar energy into electricity or heat. ... For the British rock band of the same name, see Amplifier (band) An amplifier can be considered to be any device that uses a small amount of energy to control a source of a larger amount of energy, although the term today usually refers to an electronic amplifier. ...

Conductive polymers are present in most mammal tissues where electrical conduction or transduction from light or sound are necessary, including the skin, eye, inner ear, and brain. Its electronic conductivity seems to be the underlying mechanism for absorption of light, and electron-phonon interactions are exploited in hearing [1]. See the main article: Melanin. Biological tissue is any substance made up of cells that perform a similar function within an organism. ... The word transduction has several meanings: In developmental psychology, transduction is reasoning from specific cases to specific cases, typically employed by children. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. ... A schematic representation of hearing. ... A close-up of human skin. ... Closeup of a blue-green human eye. ... A human ear An ear is the organ used by a human or an animal to detect sound waves. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ...

Contents

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