Poly(3,4-ethylenedioxythiophene) (PEDOT or PEDT; ''IUPAC'' name poly(2,3-dihydrothieno ,4-''b''1,4]dioxane-5,7-diyl)) is a

conducting polymer Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that Electrical conductance, conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage ...

based on

3,4-ethylenedioxythiophene 3,4-Ethylenedioxythiophene (EDOT) is an organosulfur compound with the formula C2H4O2C4H2S. The molecule consists of thiophene, substituted at the 3 and 4 positions with an ethylene glycolyl unit. It is a colorless viscous liquid. EDOT is the pr ...

or EDOT. It was first reported by Bayer AG in 1989.

Polymer

PEDOT possesses many advantageous properties compared to earlier conducting polythiophenes like 3-alkylthiophenes. For example, the

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

is optically transparent in its

conducting Conducting is the art of directing a musical performance, such as an orchestral or choral concert. It has been defined as "the art of directing the simultaneous performance of several players or singers by the use of gesture." The primary duti ...

state and has high stability, moderate band gap, and low

redox potential Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...

. Its major disadvantage is its poor

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

, which is partly circumvented by use of

composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...

s such as PEDOT:PSS and

PEDOT-TMA Poly(3,4-ethylenedioxythiophene)-tetramethacrylate or PEDOT-TMA is a p-type conducting polymer based on 3,4-ethylenedioxylthiophene or the EDOT monomer. It is a modification of the PEDOT structure. Advantages of this polymer relative to PEDOT (o ...

. The polymer is generated by

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

. The process begins with production of the radical cation of EDOT monomer, ₂H₄O₂C₄H₂Ssup>+. This cation adds to a neutral EDOT followed by deprotonation. The idealized conversion using peroxydisulfate is shown: :n C₂H₄O₂C₄H₂S + n (OSO₃)₂²⁻ → ₂H₄O₂C₄Ssub>n + 2n HOSO₃⁻ Polymerization is usually conducted in the presence of

polystyrene sulfonate Polystyrene sulfonates are a group of medications used to treat high blood potassium. Effects generally take hours to days. They are also used to remove potassium, calcium, and sodium from solutions in technical applications. Common side effects ...

(PSS), which acts as a template. PSS also provides a counter ion, which balances the charges in the reaction and hinders the formation of by-products such as 3,4-ethylenedioxy-2(5H)-thiophenone, and keeps the PEDOT

monomer In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Mo ...

s dispersed in water or aqueous solutions. The resulting PEDOT:PSS composite can be deposited on a conductive support such as

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Platinu ...

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...

glassy carbon Glass-like carbon, often called glassy carbon or vitreous carbon, is a non-graphitizing, or nongraphitizable, carbon which combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resis ...

, and indium tin oxide.

Uses

Applications of PEDOT include electrochromic displays and antistatics. PEDOT has also been proposed for

photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...

s, printed wiring, and sensors. PEDOT has been proposed for use in biocompatible interfaces.

References

{{Reflist Organic polymers Organic semiconductors Transparent electrodes Conductive polymers

Polymer

Uses

Further reading

References