Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
1999-06-01
2001-03-06
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
Reexamination Certificate
active
06197921
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to conducting polymers and their use as electrodes in various devices, and, in particular, to polymers resulting from electropolymerization of novel aniline-thiophene monomers.
The electrical conductivity (&sgr;) of most organic materials at room temperature is quite small (&sgr;<10
−10
ohm
−1
cm
−1
). Over the last two decades, the synthesis of organic molecules with electrical properties approaching those of metals have been the focus of considerable attention. Because organic polymers generally have elasticity, strength and plasticity, they offer significant advantages over non-polymeric materials in the manufacture of electronic materials. Macromolecular substances can now be tailored to perform as semiconductors or even as true organic metals.
The field of organic metals is dominated by two types of molecular structures: linearly conjugated &pgr;-systems and charge-transfer complexes which form stacks of &pgr;-systems in the solid state. In the former systems, electrons move rapidly along a partially oxidized or reduced molecular chain. Examples of linear &pgr;-conjugated systems are polypyroles, polythiophenes, polyanilines, polyacetylenes and polyarylenes. In charge-transfer complexes, electrons move along a partially oxidized or reduced stack molecules. In either case, the electrical, optical and magnetic properties are a complex function of the solid state structure, and efforts have been made to prepare and study model compounds for these systems, primarily in solution.
Among the families of organic synthetic metals, poly(thiophene) (PTh) and polyaniline (PANI) a nd their derivatives may be the most extensively prepared and studied systems in recent years. While the former, as a whole, has generally higher p-doped conductivity, the latter enjoys a better temporal stability with respect to conductive properties at ambient conditions.
We have synthesized new electro-active monomers, as well as polymers therefrom, comprising thiophene and aniline units linked by a direct C—C bond.
Accordingly, it is an object of the present invention to provide new polymers.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from a reading of the following detailed disclosure of the invention.
SUMMARY OF THE INVENTION
In accordance with the present invention there are provided novel polymers produced by the polymerization of monomers of the formulae:
These monomers are synthesized by the palladium-catalyzed coupling reaction of 1-halo-4-nitrobenzene with the corresponding 2-(tributylstannyl)thiophene, followed by reduction of the nitro intermediates, as shown in the examples which follow. The coupling reaction works well in dioxane or toluene at reflux with tetrakis-(triphenylphosphine)palladium(0), Pd(PPh
3
)
4
.
These monomers are preferably electrochemically polymerized. Electrochemical polymerization of the above-described monomers can be carried out according to the methods generally employed for electrochemical polymerization of thiophene, pyrrole, and the like. The electrochemical copolymerization is carried out by cyclic voltammetry, by subjecting a mixture of monomer, solvent and electrolyte to one of the following conditions: (a) setting the potentiostat at a constant electrical potential where the monomer is optimally oxidized; (b) setting the potentiostat at a constant current value; or (c) repeated scanning between the redox potentials of the monomers. Typically, all three conditions are tested for a new monomer in order to select one as the optimal condition for achieving electropolymerized polymer films with the required stability and thickness. If the oxidation-reduction cycle can be repeated several times and the polymer film deposited on the electrode exhibits reproducible cyclic voltammetric (current-voltage) characteristics, it is then deemed to be electrochemically stable and well-behaved.
The solvents which can be used in the present invention may be either aqueous or nonaqueous, although a solution of the aforesaid electrolyte in a nonaqueous organic solvent is preferred. The organic solvents used herein are preferably aprotic and have high dielectric constants. For example, ethers, ketones, nitrites, amines, amides, sulfur compounds, phosphoric ester compounds, phosphorous ester compounds, boric ester compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds and the like can be employed. Of these, ethers, ketones, nitriles, phosphoric ester compounds, phosphorous ester compounds, boric ester compounds, chlorinated hydrocarbons and carbonates are preferred. Specific examples of suitable solvents include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, 1,2-dichloroethane, gamma-butyrolactone, valerolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, dimethylformamide, dimethyl sulfoxide, ethyl phosphate, methyl phosphate, ethyl phosphite, methyl phosphite, 3-methylsulfolane, etc. Among these, nitriles and carbonates are especially preferred in order to increase the response speed. These organic solvents may be used alone or in combination.
Specific examples of electrolyte which can be used in the present invention include tetraphenylarsonium chloride, tetraphenylphosphonium chloride, tetra(n-butyl)ammonium bromide, lithium bromide, tetra(n-butyl)ammonium hexafluorophosphate, and tetra(n-butyl)ammonium perchlorate (TBAP). These examples are merely illustrative and not limiting.
Within the context of the implementation of the process in accordance with the invention, the electrochemical reactions are advantageously carried out at the surface of an electrode. By measuring the current delivered during the reaction, the electrode effectively makes it possible to monitor the progress of the polymerization reaction (for example the thickness of the polymer formed) or the progress of subsequent reactions carried out on the copolymer.
The resulting polymers have repeating units of the formula:
The following examples illustrate the invention:
In the examples which follow, electrochemical characterization and electropolymerization experiments were conducted using an EG&G Princeton Applied Research Model 273 potentiostat/galyanostat; these experiments were conducted in a three-electrode cell containing 10 mM monomer and 0.1 M tetra-n-butylammonium perchlorate (TBAP) in CH
3
CN (Th—An) or CH
2
Cl
2
(Th—Th—An, EDOT—An and C
10
OThOC
10
—An). Gold button cell and platinum plate were used as the working and counter electrodes. Freshly prepared 0.1M Ag/Ag
+
in CH
3
CN was used as a reference electrode. The electrochemical cell was enclosed in an inert chamber with a positive nitrogen gas flow throughout the experiment. The nitrogen gas was passed through a purifier before entering the chamber. A standard scan of the electrolyte/solvent system revealed the system to be electrochemically stable between 1.2 V and −1.0 V. A scan rate of 25 mV/s was typically used.
REFERENCES:
patent: 4940517 (1990-07-01), Wei
patent: 5527434 (1996-06-01), Hamnett et al.
D. Nagvekar, B. Sankaran, L-S Tan, Synthesis and Electrochemical Characterization of Electro-Active Monomers Containing Directly Bonded Aniline-Thiophene, Aniline-bithiophene and Anilne-Ethylenedioxythiophene Structures, Polymer Preprints, vol. 39, No. 2, Aug. 1998, pp 548-549, published Jul. 16, 1998.
S.C. Ng, L.G. Xu, H.S.O. Chan, A novel conductive polymer: poly[4-(2-thienyl)benzenamine], J. Mater. Sci. Letters, 16(1997), 1738-1740. (no month given.).
J. Guay, M. Leclerc, L.H. Dao, Conducting polymer derived from 4-aminobiphenyl, J. Electroanal. Chem., 251(1988), 31-39. (no month given.).
D.R. McKean, G. Parrinello, A.F. Renaldo, J.K. Stille, Synthesis of Functionalized Styrenes via Palladium-Catalyzed Coupling of Aryl Bromides with Vinyl Tin Reagents, J. Org. Chem., 1987, 52, 422-424. (no month given.).
S.C. Ng, L. Xu, Poly&ls
Nagvekar Devdatt S.
Sankaran Balasubramanian
Tan Loon-Seng
Bricker Charles E.
Henderson Christopher
Kundert Thomas L.
The United States of America as represented by the Secretary of
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