Solid-State Synthesis of a Conducting Polythiophene via an Unprecedented Heterocyclic Coupling Reaction

Hong Meng, Dmitrii F. Perepichka, Michael Bendikov, Fred Wudl, Grant Z. Pan, Wenjiang Yu, Wenjian Dong, Stuart Brown

Research output: Contribution to journalArticle

164 Citations (Scopus)

Abstract

Prolonged storage (∼2 years) or gentle heating (50-80 °C) of crystalline 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) affords a highly conducting, bromine-doped poly(3,4-ethylenedioxythiophene) (PEDOT), as confirmed by solid-state NMR, FTIR, CV, and vis-NIR spectroscopies. The novel solid-state polymerization (SSP) does not occur for 2,5-dichloro-3,4-ethylenedioxythiophene (DCEDOT), and requires a much higher temperature (>130 °C) for 2,5-diiodo-3,4-ethylenedioxythiophene (DIEDOT). X-ray structural analysis of the above dihalothiophenes reveals short Hal⋯Hal distances between adjacent molecules in DBEDOT and DIEDOT, but not in DCEDOT. The polymerization may also occur in the melt but is significantly slower and leads to poorly conductive material. Detailed studies of the reaction were performed using ESR, DSC, microscopy, and gravimetric analyses. SSP starts on crystal defect sites; it is exothermic by 14 kcal/mol and requires activation energy of ∼26 kcal/mol (for DBEDOT). The temperature dependence of the conductivity of SSP-PEDOT (σrt = 20-80 S/cm) reveals a slight thermal activation. It can be further increased by a factor of 2 by doping with iodine. Using this approach, thin films of PEDOT with conductivity as high as 20 S/cm were fabricated on insulating flexible plastic surfaces.

Original languageEnglish
Pages (from-to)15151-15162
Number of pages12
JournalJournal of the American Chemical Society
Volume125
Issue number49
DOIs
Publication statusPublished - Dec 10 2003

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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