3,4-Ethylenedioxythiophene on:
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3,4-Ethylenedioxythiophene (EDOT) is an organosulfur compound with the formula C2H4O2C4H2S. The molecule consists of
EDOT is often prepared from C4 precursors such as
thiophene
Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its react ...
, substituted at the 3 and 4 positions with an ethylene glycolyl unit. It is a colorless viscous liquid.
EDOT is the precursor to the polymer PEDOT
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 based on 3,4-Ethylenedioxythiophene, 3,4-ethylenedioxythiophene or EDOT. It was first reported by Baye ...
, which is found in electrochromism, electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.
Synthesis and polymerization
The original synthesis proceeded via the diester of 3,4-dihydroxythiophene-2,5-dicarboxylate.
EDOT is often prepared from C4 precursors such as butanediol Butanediol, also called butylene glycol, may refer to any one of four stable structural isomers:
* 1,2-Butanediol
* 1,3-Butanediol
*1,4-Butanediol
*2,3-Butanediol
2,3-Butanediol is the organic compound with the formula (CH3CHOH)2. It is classif ...
and butadiene
1,3-Butadiene () is the organic compound with the formula (CH2=CH)2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two vi ...
via routes that produce the thiophene and dioxane rings in separate steps. Representative is the reaction of 2,3-butanedione, trimethyl orthoformate
Trimethyl orthoformate (TMOF) is the organic compound with the formula HC(OCH3)3. A colorless liquid, it is the simplest orthoester. It is a reagent used in organic synthesis for the formation of methyl ethers. The product of reaction of an ald ...
, and ethylene glycol
Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...
to form the dioxane. Sulfidization with elemental sulfur gives the bicyclic target.
EDOT is converted into the conducting polymer
Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers ...
PEDOT
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 based on 3,4-Ethylenedioxythiophene, 3,4-ethylenedioxythiophene or EDOT. It was first reported by Baye ...
by oxidation. The mechanism for this conversion begins with production of the radical cation DOTsup>+, which attacks a neutral EDOT molecule followed by deprotonation. Further similar steps result in the dehydropolymerization. The idealized conversion using peroxydisulfate
The peroxydisulfate ion, , is an oxyanion, the anion of peroxydisulfuric acid. It is commonly referred to as persulfate, but this term also refers to the peroxomonosulfate ion, . It is also called ''peroxodisulfate''. Approximately 500,000 tons o ...
is shown
:n C2H4O2C4H2S + n (OSO3)22− → 2H4O2C4Ssub>n + 2n HOSO3−
For commercial purposes, the polymerization is conducted in the presence of polystyrenesulfonate.
References