Conductive polymers

Conductive polymers are organic polymer semiconductors.

Chemistry

Common classes of organic conductive polymers include poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(aniline)s, and poly(para-phenylene vinylene)s. Classically, these compounds are known as acetylene, polyaniline, etc. "blacks" or "melanins". The melanin pigment in animals is generally a mixed copolymer of polyacetylene, polypyrrole, and polyaniline.

Related Topics:
Poly(acetylene)s - Poly(pyrrole)s - Poly(thiophene)s - Poly(aniline)s

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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 and p-type semiconductors, respectively. Not to be confused with semiconductor doping, which involves replacing an atom in a lattice, polymers can be 'doped' by adding chemical reactants to oxidise (or sometimes reduce) the system to push electrons into the conducting orbitals within the already (potentially) conducting system. (In a silicon lattice, the system is far from conducting to begin with!) 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. A 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).

Related Topics:
Phosphorus - Boron - Redox - Melanin - Oxidant - Iodine - Bromine - Reductant - Alkali metals - Electrochemical - Electrode - Electrolyte - Insoluble - Ion

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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 more common in research, because it is easier to exclude oxygen from a solvent in a sealed flask; however, there are likely no commercialized n doped conductive polymers.

Related Topics:
Atmosphere - Oxygen - Oxidizing - Inert - Argon - Solvent - Flask

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Conjugation

The extended conjugation of a conductive polymer tends to give rise to fluorescence which has lead to the rapid development of polymer-based light emitting devices (OLEDs) and organic photovoltaic devices.

Related Topics:
Conjugation - Fluorescence - OLED - Photovoltaic

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Properties

The biggest advantage of conductive polymers is processibility. Conductive polymers are also plastics (which are organic polymers) and therefore can combine the mechanical properties (flexibility, toughness, elasticity, etc.) of plastics with the high electrical conductivities of a doped conjugated polymer.

Related Topics:
Plastics - Elasticity

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