Self-Doped Polythiophenes

Self-Doped Conducting Polymers M.S. Freund and B.A. Deore 2007 John Wiley 8c Sons, Ltd 

Eigure 4.2 UV-Vis absorption spectra of poly(3-thiophene butanesulfonic acid) (cast from water dash curve) and for a solution of the same polymer in water (solid curve). (Reprinted from Synthetic Metals, 20, A. O. Patil, Y. Ikenoue, N. Basescu, N. Colaneri, J. Chen, E. Wudl, A. J. Heeger, 151. Copyright (1987), with permission from Elsevier.) 

In further studies, the self-doping mechanism of these polymers was verified by cyclic voltammetry, pH measurements and atomic absorption spectroscopy [17,20]. The cyclic voltammograms of the sodium salt and acid forms of poly(3-thiophene butanesulfonate) cast films are shown in 

Chen et al. [24] studied the structure and effect of the side chain length on the doping level of self-doped poly(n-(3 -thienyl)alkanesulfonic acid)s with alkanes of carbon numbers 2, 6 and 10. They suggested that self-doping of poly(n-(3 -thienyl)alkanesulfonic acid)s is dependent on the side chain length (for details see Chapter 1 Section 1.4.3). In subsequent work, Chen et al. reported the irreversible thermal dedoping 

70 °C under vacuum (B) variations of conductivity of P3TESH films with time at different temperatures under vacuum. (Reprinted with permission from Chemistry of Materials, 9, 2750. Copyright (1997) American Chemical Society.) 

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Figure 1.20 Various self-doped polythiophene derivatives.

A. Berlin, G. Schiavon, S. Zecchin, G. Zotti, New highly conjugated self-doped polythiophenes functionalized with alkyl ammonium groups, Synthetic Metals 2001,119,153. 

The chemical synthesis of self-doped polythiophene was first reported by Ikenoue et al. [21]. They synthesized self-doped poly(3-(3 -thienyl)pro-panesulfonate) in aqueous media using ferric chloride as an oxidizing agent. The electrochemical polymerization of the monomer, 3-(3 -... 

Y. A. Udum, K. Pekmez, A. Yildiz, Electropolymerization of self-doped polythiophene in acetonitrile containing FSO3H, Synthetic Metals 2004, 142, 1. 

Self-doped polythiophenes characterized by lower oxidation potentials and improved electrochemical behavior have been synthesized from 3-((w-carboxy-... 

A self-doped polythiophene has been prepared from 3 -propanesulfonate terthiophene (24) selected for the lower oxidation potential of the trimer compared with the monomer. This compound shows its electrolyte character by electropolymerizing in acetonitrile without addition of supporting electrolyte [113]. Self-doped polythiophenes with lower oxidation potentials and improved electrochemical behaviour have been prepared from 3-(co-carboxyalkyl)thiophenes with alkyl chains containing 4 to 14 carbon atoms (25) [173]. 

Self-doped polythiophenes. . 834 3.1 Sulfonic acid derivatives. . . 845... 

Preliminary investigations of self-doped polythiophenes did not specify whether the cation species associated with the sulfonate group was expelled or whether an additional anion was incorporated during electrochemical oxidation of the polymer. Using cyclic voltammetry, pH measurements, and atomic absorption spectroscopy, it was established that the hydrogen ion associated with poly(cu-(3-thienyl)alkanesulfonic acids... 

Self-doping has also been studied with poly(3-alkylsulfonate-thiophenes) [7-9]. The self-doped polythiophenes have a SO3H group at the end of the alkyl side chain. However, in order to obtain good conductivities, the charge transfer reaction has to be driven electrochemically to remove the cation (H+ or Na+) of the sulfonic acid out of the polymer. Otherwise this kind of self-doped polythiophenes have a very low conductivity in the dried state due to the protonation of the thiophene rings [75]. 

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