Self-acid-doped highly conducting polythiophenes

Details Self-acid-doped highly conducting polythiophenes Self-acid-doped highly conducting polythiophenes

1999-01-15

2000-04-18

Yoon, Tae

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From sulfur-containing reactant

523137, 524910, 549 66, 252500, C08G 7500, C07D33334, H01B 318, G21F 110

Patent

active

060516798

DESCRIPTION:

BRIEF SUMMARY
The invention relates to thiophenes bearing (.omega.-sulfonate)alkoxy or (.omega.-sulfonic acid)alkoxy groups and water-soluble polythiophenes bearing (.omega.-sulfonic acid)alkoxy side-chains prepared therefrom. The invention also relates to methods for the preparation of these compounds and to antistatic coatings and EMI shieldings comprising the polythiophenes.
The search for processable, stable, conducting polymers has been the goal of many studies in the past few years. Many synthetic approaches have been taken but, generally, the conducting state is obtained through a partial chemical or electrochemical oxidation (so-called doping reaction) of the conjugated moieties leading to the formation of different mobile charge carriers (radical cations, dimerized radical cations and dications).
In most cases, processability has been obtained by the introduction of large counter-ions (which are introduced during the oxidation process to preserve the electro-neutrality) or by the attachment of relatively flexible side chains. It is believed that these structural modifications decrease the attractive interchain interactions and introduce favorable interactions between the substituents and the solvent.
The addition of side-chains does not only allow an easier processing of some electroactive polymers, but can also modulate the electronic properties of the conjugated main chain. For instance, it has been reported that the introduction of strong electrondonating side-chains, e.g. alkoxy groups, decreases the oxidation potential of the resulting polymers, giving a better stability of the oxidized (and conducting) state.
In U.S. Pat. No. 5,093,033 and Macromolecules 24(1991)455, poly(3-alkoxythiophene)s are disclosed, Macromolecules 26(1993)2501 teaches poly(3,3'-dialkoxy-2,2'-bithiophene)s and poly(4,4'-dialkoxy-2,2'-bithiophene)s. Poly(3,4-cylcloalkoxythiophene)s are known from U.S. Pat. No. 4,987,042. All these materials show high and stable electrical conductivities with low absorption in the visible range when oxidized.
On the other hand, it has been found that the presence of different counter-ions in the doped state can significantly alter the stability of the electrical conductivity. For instance, it is believed that steric interactions between the flexible side-chains and the counter-ions are responsible for the poor stability of some of these conducting polymers, particularly at high temperatures. A partial solution to this problem was the attachment of ionic (e.g. sulfonate moieties) side-chains which allows the possibility to get the counter-ions covalently linked to the conjugated backbone (combined to a good solubility in water), leading to the concept of self-doped conducting polymers. For instance, U.S. Pat. No. 5,367,041 discloses self-doped zwitterionic polythiophenes bearing alkylsulfonate or alkylcarboxylate side-chains.
It is worth noting that an external redox reaction must be done onto the conjugated polymer to obtain the oxidized (conducting) state but this process does not involve the introduction of any counter-ions during the doping process.
Macromolecules 26(1993)7108 and J. Chem. Soc. Chem. Commun. (1990)1694 disclose that the preparation of the acid form of sulfonated polythiophenes(involving a sulfonic acid fuctionality) is accompanied by a partial doping (oxidation) without the use of any external oxidizing agent. Thus, the presence of a strong protonic acid, oxygen (air), and a conjugated backbone can lead to conducting (doped) polymers.
Following a new synthetic approach, water-soluble polythiophenes bearing (.omega.-sulfonic acid)alkoxy side-chains have now been synthesized showing stable, high electrical conductivities together with low absorption in the visible range.
One aspect of the invention is to provide monomers from which such polymers can be prepared. These monomers are thiophenes corresponding to formula (I) ##STR1## and bithiophenes corresponding to formulae (IIa) or (IIb) ##STR2##
In these formulae R represents a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group. R is pre

REFERENCES:
patent: 4987042 (1991-01-01), Jonas et al.
patent: 4992559 (1991-02-01), Kathirgamanathan et al.
patent: 5093033 (1992-03-01), Feldhues et al.
patent: 5367041 (1994-11-01), Wudl et al.
"A Facile Preparation of a Self-Doped Conducting Polymer", Y. Ikenoue et al. J. of the Chem. Soc., Chem. Commun. pp. 1694-1695, 1990.
"Functionalized Regioregular Polythiophenes: Towards the Development of Biochromic Sensors", Faid K. et al. Chem. Commun. (24), pp. 2761-2762, 1996.

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