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Did you know how 19th-century chemists discovered the secret to conducting polymers?
Conductive polymers, or more accurately, intrinsically conductive polymers (ICPs), are organic polymers that can conduct electricity. These compounds may have the conductivity of metals or become semiconductors. The main advantage of conductive polymers is their ease of processing, especially in terms of dispersion. Although conductive polymers are generally not thermoplastics, they are still organic materials that offer high electrical conductivity without the mechanical properties of other commercial polymers. The electrical properties of these polymers can be fine-tuned through organic synthesis methods and advanced dispersion techniques.
Historical background
The history of conductive polymers dates back to the 19th century. In the mid-term, polyaniline was first described by Henry Lesby, who studied the electrochemical and chemical oxidation products of aniline in acidic media. He noticed that the reduced form was colorless, but the oxidized form was dark blue.
"This discovery signals the potential of organic materials to conduct electrical current."
Over time, scientists discovered more conductive organic compounds, especially in the 20th century. In the 1950s, researchers reported that polycyclic aromatic compounds and egg fluorine formed charge transfer complex salts with semiconductor properties. In 1954, researchers at Bell Labs reported organic charge transfer complexes with resistance values as low as 8 Ω·cm. As these compounds were further studied, the potential of conducting polymers became apparent, and in 1977 Alan J. Seager and his team were awarded the 2000 Prize for discovering the highly conductive properties of iodine-doped polyacetylene. Nobel Prize in Chemistry.
Synthesis of conductive polymers
Conductive polymers can be synthesized by a variety of methods. One of the most commonly used methods is oxidative coupling reaction. In order to improve the solubility of polymers, some experts add solubilizing functional groups to the monomers, or solve the problem of low solubility by forming nanostructures. Chemical synthesis and electrochemical (co)polymerization are the two main synthetic methods.
“The advantage of electrochemical polymerization is the high purity of the product, but usually only a small amount of product can be synthesized at a time.”
Basic properties of conductive polymers
The conductivity of these polymers comes from certain physical processes. In traditional polymers such as polyethylene, the valence electrons are fixed in the covalent bonds of the sp3 mixture and have low mobility. In conductive polymers, the carbon atoms in the main chain are continuously sp2 mixed. Once oxidatively doped, the conductivity of these materials increases significantly.
Application prospects
Conductive polymers have shown potential in many areas, such as antistatic materials, commercial displays and battery applications. In addition, they are expected to play an important role in organic solar cells, printed electronic circuits, organic light-emitting diodes, etc. Especially since the late 1980s, organic light-emitting diodes (OLEDs) have become one of the important applications of these materials.
Future trends
In recent years, more and more attention has been paid to organic light-emitting diodes and organic polymer solar cells. New nanostructured forms of conductive polymers also inject more possibilities into the development of this field and are gradually accepted by more applications.
What innovative applications may these polymers bring in the future?
