3,4-Ethylenedioxythiophene

3,4-Ethylenedioxythiophene (EDOT) is the 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.[2]

3,4-Ethylenedioxythiophene
Names
Other names
2,3-dihydrothieno[3,4-b]-1,4-dioxin
Identifiers
Properties
C6H6O2S
Molar mass 142.17 g·mol−1
Appearance colorless liquid
Density 1.34 g/cm3[1]
Melting point 10.5 °C (50.9 °F; 283.6 K)[1]
Boiling point 225 °C (437 °F; 498 K)[1]
2.1 g/L[1]
Viscosity 11 mPa·s[1]
Hazards
Flash point 104 °C (219 °F; 377 K)[1]
360 °C (680 °F; 633 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

EDOT is the precursor to the polymer PEDOT, which is found in electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.[3][4]

Synthesis and polymerization

The original synthesis proceeded via the diester of 3,4-dihydroxythiophene-2,5-dicarboxylate.

One synthesis of EDOT.

EDOT is often prepared from C4 precursors such as butanediol and butadiene via routes that produce the thiophene and dioxane rings in separate steps. Representative is the reaction of 2,3-butanedione, trimethylorthoformate, and ethylene glycol to form the dioxane. Sulfidization with elemental sulfur gives the bicyclic target.[5]

EDOT is converted into the conducting polymer PEDOT by oxidation. The mechanism for this conversion begins with production of the radical cation [EDOT]+, which attacks a neutral EDOT molecule followed by deprotonation. Further similar steps result in the dehydropolymerization. The idealized conversion using peroxydisulfate is shown

n C2H4O2C4H2S + n (OSO3)22− → [C2H4O2C4S]n + 2n HOSO3−

For commercial purposes, the polymerization is conducted in the presence of polystyrenesulfonate.[4]

References
  1. Elschner, Andreas; Kirchmeyer, Stephan; Lovenich, Wilfried (2010). PEDOT: Principles and Applications of an Intrinsically Conductive Polymer. CRC Press. p. 51. ISBN 978-1-4200-6912-9.
  2. Jonas, F.; Schrader, L. (1991). "Conductive Modifications of Polymers with Polypyrroles and Polythiophenes". Synthetic Metals. 41 (3): 831–836. doi:10.1016/0379-6779(91)91506-6.
  3. Groenendaal, L. B.; Jonas, F.; Freitag, D.; Pielartzik, H.; Reynolds, J. R. (2000). "Poly(3,4-Ethylenedioxythiophene) and Its Derivatives: Past, Present, and Future". Adv. Mater. 12 (7): 481–494. doi:10.1002/(SICI)1521-4095(200004)12:7<481::AID-ADMA481>3.0.CO;2-C.
  4. Kirchmeyer, S.; Reuter, K. (2005). "Scientific Importance, Properties and Growing Applications of Poly(3,4-Ethylenedioxythiophene)". J. Mater. Chem. 15 (21): 2077–2088. doi:10.1039/b417803n.
  5. Hachiya, I.; Yamamoto, T.; Inagaki, T.; et al. (2014). "Two-Step Synthesis of 3,4-Ethylenedioxythiophene (EDOT) from 2,3-Butanedione". Heterocycles. 88: 607–612. doi:10.3987/COM-13-S(S)8.
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