Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-01-18
2002-04-30
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S212000, C528S214000, C528S422000
Reexamination Certificate
active
06380346
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to polyanilines, and more particularly to a heterogeneous reaction method for making functionalized polyanilines.
DESCRIPTION OF THE RELATED ART
Polyaniline, as a backbone conjugated conducting polymer, has various applications in the art. General applications of polyaniline and other conducting polymers are found in electronics, electrooptical devices, anti-corrosion, semiconductors, and microelectronics. Polyanilines, like other conducting polymers, are difficult to process due to their poor solubility in most common solvents. Substituted polyanilines with better solubility are highly desirable for those applications that require high solubility and/or high processibility. Conventional processes for preparing substituted polyaniline homopolymers or copolymers employ chemical or electrochemical oxidative polymerization methods directly from substituted aniline monomers. However, conventional processes for preparing substituted polyanilines have disadvantages. Unlike unsubstituted polyanilines that have highly conjugated 1,4-linkage backbone structures, the substituted polyaniline homopolymers or copolymers prepared from conventional processes often result in conjugation defects, The conjugation defects are due to the competing electronic influence from the substituents which lead to higher probability of forming the less conjugated 1,3-linkage backbone structure.
Another method for making functionalized polyanilines is the concurrent reduction and substitution reaction method (the CRSR method) using a homogeneous reaction. According to the homogeneous CRSR method, amino-substituted polyanilines are prepared by reacting dialkylamines with a homogeneous solution of unsubstituted polyaniline emeraldine base (i.e., with a solution state form of unsubstituted polyaniline emeraldine base) which contains about 25 mol % of diiminoquinoid ring units based on the polyaniline repeat units. The dialkylamines attack and then attach at the meta-position of the protonated quinoid ring, followed by a 1,3-proton shift of the meta-proton to the para-imine nitrogen, and a dialkylamino-substituted benzenoid ring is formed as a result. Unsubstituted diiminoquinoid ring repeat units are converted into dialkylamino-substituted diaminobenzenoid rings. The dialkylamino functional groups attach to the polyaniline backbones at the ortho- or meta-positions, and the most conjugated 1,4-linkage backbone structures of their parent polyanilines are therefore preserved. However, according to the homogeneous CRSR method the dialkylamines only attack the quinoid rings of the emeraldine base. As a result, the maximum amount of the substituent group that can be incorporated is limited to about 25 mol % of the polyaniline repeat units. The homogeneous CRSR method also has difficulties in effectively separating the resultant polyaniline from the chemical reagent solution, in purifying the resultant polyaniline, and in keeping the chemical reagent solution from being contaminated by the separation process. The homogeneous CRSR method also has a very limited selection of solvent media, due to the poor solubility of polyaniline in most solvents.
There is thus a general need in the art for an improved method for making functionalized polyanilines. In particular, a need exists in the art for preparing substituted polyanilines with a lower likelihood of conjugation defects. Furthermore, a method for making functionalized polyanilines that efficiently separate the resultant polyaniline and the chemical reagent solution, and overcome the above noted and other disadvantages in the art.
SUMMARY OF THE INVENTION
The present invention is related to a new and easy method for making functionalized polyanilines. In particular, the present invention provides a feasible and effective method to carry out the concurrent reduction and substitution reaction method (the CRSR method) for solid state forms of polyanilines using a heterogeneous reaction. In addition to unsubstituted polyanilines, the method according to the invention can also be used for preparing substituted polyaniline homopolymers or copolymers. Numerous advantages are provided by the present invention over prior art methods using the homogeneous CRSR method, such as ease in separating the resultant polyanilines in their solid state forms from the chemical reagent solution, convenience in purifying the resultant polyanilines, ease in keeping the chemical reagent solution from contamination, which allows the reuse of the chemical reagent solution and offers a broader selection of solvent media. The present invention also allows the introduction of more than one type of substituents in a controlled sequential manner, thereby providing the polymer with multiple advantageous characteristics such as high solubility plus self-doping ability. The present invention also allows precise control of the degree of substitution (or derivatization) and the oxidation state of the resulting polyanilines, which enables optimal performance of subsequent applications such as anti-corrosion coatings, functional polyaniline electrodes, biosensors or chemical sensors. Furthermore, the method according to the present invention is advantageously less chemically consuming, more economical, and more environmentally friendly comparing with the homogeneous CRSR method.
More particularly, an embodiment of the method of the present invention comprises the steps of:
(a) providing polyaniline in a solid state form; and
(b) subjecting the solid state polyaniline to a reaction treatment with a solution of reactive chemical reagent(s) in a selected solvent or solvent mixture for a period of time, the solvent or solvent mixture is capable of dissolving or dispersing the chemical reagent(s) and swelling or wetting the solid state polyaniline, and the chemical reagent(s) is capable of functionalizing the solid state polyaniline and transforming the backbone of the solid state polyaniline into a more reduced form.
Another embodiment of the method of this invention comprises the steps of:
(a) providing polyaniline in a solid state form;
(b) subjecting the solid state polyaniline to a redox treatment to convert the backbone of the solid state polyaniline into a desirable oxidation state;
(c) subjecting the resultant polyaniline to a reaction treatment with a solution of reactive chemical reagent(s) in a selected solvent or solvent mixture for a period of time, where the solvent or solvent mixture is capable of dissolving or dispersing the chemical reagent(s), and swelling or wetting the solid state polyaniline, where the chemical reagent(s) is capable of functionalizing the solid state polyaniline and transforming the backbone of the solid state polyaniline into a more reduced form; and
(d) repeating steps (b) and/or (c);
wherein steps (b) and (c) can be reversed, or step (b) or step (c) can be omitted as desired in the first cycle or any subsequent repeat cycles of the redox/reaction treatments.
REFERENCES:
Han, Chien-Chung et al., “Concurrent Reduction and Modification of Polyaniline Emeraldine Base with Pyrrolidine and Other Nucleophiles”, Chemical Communications 1997, pp. 553-554.
Han, Chien-Chung et al., “Combination of Electrochemistry with Concurrent Reduction and Substitution Chemistry to Provide a Facile and Versatile Tool for Preparing Highly Functionalized Polyanilines”, vol. 11, No. 2, Chemistry of Materials, pp. 480-486, Jan. 20, 1999.
Green, Arthur G. et al., “Aniline-black and Allied Compounds. Part II”, pp. 1117-1123, Journal of Chemical Society (London), 1912.
Genies, E. M. et al., “Polyaniline: A Historical Survey”, Synthetic Metals 1990, pp. 139-182.
Kobayashi, Tetsuhiko et al., “Electrochemical Reactions Concerned with Electrochromism of Polyaniline Film-Coated Electrodes”, vol. 117, J. Electroanal. Chem. 1984, pp. 281-291.
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