Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2002-12-18
2004-06-29
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S373000, C528S380000, C528S403000, C528S425000, C528S480000, C528S491000
Reexamination Certificate
active
06756473
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of neutral polythiophenes based on 3,4-alkylenedioxythiophenes, in particular 3,4-ethylenedioxythiophene (also 2,3-dihydrothieno[3,4-b][1,4]dioxine), neutral polythiophenes soluble in organic solvents, and their use.
2. Brief Description of the Prior Art
The pertinent class of compounds which consists of the &pgr;-conjugated polymers has been the subject of numerous publications in recent decades. They are also referred to as conductive polymers or as synthetic metals. Owing to the considerable delocalization of the &pgr;-electrons along the main chain, these polymers exhibit interesting (nonlinear) optical properties and are good electrical conductors after oxidation or reduction. Consequently, these compounds can be used in various practical applications, such as, for example, in data storage, optical signal processing, suppression of electromagnetic interference (EMI) and conversion of solar energy, and in rechargeable batteries, light-emitting diodes, field effect transistors, circuit boards, sensors, capacitors and antistatic materials.
Examples of known &pgr;-conjugated polymers are polypyrroles, polythiophenes, polyanilines, polyacetylenes, polyphenylenes and poly(p-phenylene-vinylenes). A particularly important and industrially used polythiophene is poly(ethylene-3,4-dioxythiophene), which has very high conductivities in its doped form, cf. for example EP 339 340 A2. The preparation of the doped poly(ethylene-3,4-dioxythiophene) is effected according to EP 339 340 A2 by oxidative polymerization of 3,4-ethylenedioxythiophene. The processibility of the product is achieved, for example, by the use of poly(styrenesulphonate) as a counter ion in aqueous dispersion.
In comparison, products which are likewise highly conductive but unprocessible are obtained, for example in the form of coatings, by electropolymerization (e.g. “Q. Pei, G. Zuccarello, M. Ahlskog and O. Inganäs, Polymer 35 (1994), pages 1347-1351”).
According to “T. Yamamoto & M. Abla, Synth. Met. 100 (1999), pages 237-239”, it is not possible completely to eliminate the doping of a doped poly(ethylene-3,4-dioxythiophene) prepared according to EP 339 340 A2 or prepared in a similar manner by oxidative polymerization, and thus to prepare a neutral—and thereby undoped—poly(ethylene-3,4-dioxythiophene). Doping according to Yamamoto means oxidation and thereby generating positive charged poly(ethylene-3,4-dioxythiophene).
According to “S. Garreau, G. Louarn, J. P. Buisson, G. Froyer, S. Lefrant, Macromolecules 32, (1999) pages 6807-6812”, it is just as impossible completely to dedope the electrochemically produced doped poly(ethylene-3,4-dioxythiophene) by an electrochemical method.
Neutral poly(ethylene-3,4-dioxythiophene) has therefore always been prepared to date by so-called reductive, organometallic synthesis from 2,5-dihalogeno-ethylene-3,4-dioxythiophene. “Synth. Met. 100 (1999), pages 237-239” and “Polymer 43 (2002), pages 711-719” disclose a process for the preparation of neutral, undoped poly(ethylene-3,4-dioxythiophene) by dehalogenating polycondensation of 2,5-dichloro-ethylene-3,4-dioxythiophene in the presence of bis(1,5-cyclooctadiene)nickel(0). However, only an insoluble poly(ethylene-3,4-dioxythiophene) can be obtained by this process.
“J. Mater. Chem. 11, (2001) pages 1378-1382” describes the preparation of soluble, neutral, undoped poly(ethylene-3,4-dioxythiophene) by polycondensation of 2,5-dibromo-ethylene-3,4-dioxythiophene in the presence of Ni(0) prepared in situ. As a result of the preparation, however, a material synthesized in this manner contains organically bound bromine. Owing to the danger of HBr or bromide elimination, such chemically noninert terminal groups on the polymer are undesired in applications in the electronics industry. Moreover, this product has also been described as being only partly soluble in dimethylacetamide.
In addition, the processes, described in “Synth. Met. 100 (1999), pages 237-239”, “J. Mater. Chem. 11, (2001) pages 1378-1382” and “Synth. Met. 119 (2001), pages 381-382” are not economical compared with simple oxidative polymerization processes, owing to the additional synthesis step via the 2,5-dihalogenoethylene-3,4-dioxythiophene and the use of expensive, sensitive organometallic reagents.
One possibility for obtaining soluble, neutral and undoped derivatives of poly(ethylene-3,4-dioxythiophene) which are soluble in organic solvents by oxidative polymerization consists in substitution of the ethylene unit by alkyl or alkoxymethyl groups having 10 or more C atoms. Correspondingly substituted poly(ethylene-3,4-dioxythiophenes) are described in “Adv. Mater. 12, (2000) pages 481-494”, “Polym. Mater. Sci. Eng. 72, (1995) page 319 et seq.”, “Macromolecules 30, (1997) page 2582 et seq.”, “Macromolecules 29, (1996) page 7629 et seq.”, “Chem. Mater. 10, (1998) page 896 et seq.”, “Synth. Met. 102, (1999) page 967 et seq.”, “J. Chim. Phys. 95, (1998) page 1258 et seq.”, “Synth. Met. 101, (1999) pages 7-8” and “Chem. Mater. 8, (1996) pages 769-776”. Common to all articles mentioned is that neutral and therefore undoped derivatives of poly(ethylene-3,4-dioxythiophene) which are soluble in organic solvents are obtained only when the substituents on the ethylene unit of the 3,4-ethylenedioxythiophene have at least 10 carbon atoms.
“Polymer 42 (2001), pages 7229-7232” describes a neutral, undoped polymer of 2-n-hexyl-2,3-dihydrothieno[3,4-b][1,4]dioxine units. However, the preparation is effected via the complicated synthesis method described in “Synth. Met. 100 (1999), pages 237-239”, by polycondensation of the 2,5-dichlorothiophene derivative in the presence of Ni(0); on the other hand, the oxidative synthesis was designated as being unsuitable as the preparation method.
EP 686 662 A2 mentions a neutral poly(ethylene-3,4-dioxythiophene). However, the polymerization is carried out according to EP 339 340 A2 and EP 440 957 A2. However, doped, nonneutral poly(ethylene-3,4-dioxythiophene) is prepared in this manner. A comparison of the properties of poly(ethylene-3,4-dioxythiophene) prepared according to EP 686 662 A2 with the properties of neutral poly(ethylene-3,4-dioxythiophene) which is without a doubt undoped and which is prepared according to “Synth. Met. 100 (1999), pages 237-239” or “J. Mater. Chem. 11, (2001) pages 1378-1382” also shows that EP 686 662 A2 by no means describes neutral poly(ethylene-3,4-dioxythiophene).
No process is known to date for the preparation of neutral and therefore undoped poly(ethylene-3,4-dioxythiophene) or derivatives which carry a C
1
-C
9
-alkyl substituent on the ethylene unit by an oxidative method.
The preparation of a completely halogen-free poly(ethylene-3,4-dioxythiophene) which is also soluble in organic solvents has been just as impossible to date.
It is an object of the present invention to prepare neutral poly(ethylene-3,4-dioxythiophene) which is soluble in organic solvents and free of organically bound halogen, or poly(ethylene-3,4-dioxythiophene) derivatives substituted by short chains and unknown to date in neutral form and in a form dissolved in organic solvents, by an economical and simple method.
SUMMARY OF THE INVENTION
The invention thus relates to a process for the preparation of neutral compounds of the general formula (I),
in which
R
1
and R
2
, independently of one another, each represent H or C
1
to C
9
-alkyl, it also being possible for R
2
to represent CH
2
—O—R
3
, with R
3
=H or C
1
to C
9
-alkyl, cycloalkyl or aralkyl, when R
1
represents H, and
n represents an integer from 2 to 200,
by reaction of monomers of the general formula (II),
in which
R
1
and R
2
have the abovementioned meanings,
with an oxidizing agent, the reaction being carried out in an organic solvent and the oxidizing agent being used in an amount of 50 to 99.9% of the stoichiometrically required amount.
DETAILED DESCRIPTION OF THE INVENTION
The invention is described more fully
Kirchmeyer Stephan
Reuter Knud
Akorli Godfried R.
Bayer Aktiengesellschaft
Eyl Diderico van
Truong Duc
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