NL9201275A - METHOD FOR MANUFACTURING AN ELECTRICALLY CONDUCTIVE POLYMER - Google Patents

Description

METHOD FOR MANUFACTURING AN ELECTRICALLY CONDUCTIVE POLYMER

The invention relates to a method for manufacturing an electrically conductive polymer, wherein polymerizable monomer units polymerize in an reaction mixture to form an electrically conductive polymer in the presence of a catalyst, which contains a strongly oxidizing cation and a stability-promoting anion.

Such a method is known from US-A-4,697,001. According to the method described herein, an electrically conductive polypyrrole is prepared by polymerizing pyrrole monomers in solution in the presence of a catalyst. The catalyst contains a strong oxidizing cation and a relatively large anion. The relatively large anion has a stabilizing effect on the electrically conductive properties of the formed electrically conductive polymer and also acts as a dopant, thereby improving the electrically conductive properties of the electrically conductive polymer. The produced electrically conductive polymer is recovered as a powder by a precipitation step.

The use of the method described in US-A-4,697,001 for manufacturing an electrically conductive polymer with good electrically conductive properties has a great drawback. In the presence of the catalyst, the polymerization reaction of the monomer units is initiated immediately. As a result, an electrically conductive polymer is immediately obtained, which precipitates in the reaction mixture as a powder. The powder thus formed can then hardly be molded, if at all, into a coherent molding compound.

The object of the invention is to provide a method in which the above-mentioned drawback does not occur.

The process of the invention is characterized in that the polymerizable monomer units are obtained by in situ activation of precursor monomers.

With the method according to the invention it is possible to shape molding compositions with simple processing steps and to manufacture products containing electrically conductive polymers. Early polymerization is prevented; this takes place at a time to be determined by yourself. In the process according to the invention, the precursor monomers are brought into the desired form, after which they can be activated in situ at any time to polymerize monomer units. The activated polymerizable monomer units then polymerize to an electrically conductive polymer. Molding compositions can be manufactured with the method according to the invention, in which relatively small amounts of electrically conductive polymer are sufficient to achieve good electrically conductive properties.

According to the invention, a precursor monomer is intended to mean a molecule which as such cannot polymerize under the prevailing process conditions, even when a catalyst is present. However, after a simple conversion step, this molecule is converted into a polymerizable monomer unit. This transformation step may involve removing a blocking group which shields one or more reactive sites. It is also possible that an electron withdrawing group, which increases the oxidation potential of the molecule, thereby preventing polymerization, is removed. In another embodiment, an intramolecular reaction, such as, for example, a retro-Diels-Alder reaction, takes place to convert a precursor monomer into a polymerizable monomeric unit.

With the method of the invention, any precursor monomer, which after activation becomes a polymerizable monomer unit from which an electrically conductive polymer can be formed, is suitable for use.

Suitable precursor monomers are, for example, molecules having a structure according to formula (I), wherein

R 1 is hydrogen, -C (0) 0H, -C (0) C (0) 0H, -C (0) H, -SO 3 H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C (O) 0H, or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C (O) 0H, or a halogen; R 4 is hydrogen, -C (0) 0H, -C (0) C (0) 0H, -C (0) H, -SO 3 H, -I or -Br; with the proviso that R1-R4 are not all hydrogen at the same time, and that R2 and R3 can both be part of a closed ring structure.

For formula (I), reference is made to the formula sheet.

Preferably, the precursor monomer is pyrrole-2-carboxylic acid. The synthesis of this precursor monomer is described in J. Am. Pharm. Assoc. 45, 509 (1956). In the precursor monomer of formula I, all combinations of X, R1, R2, R3 and R4 are possible. The R1 and R4 groups can be thermally or photochemically eliminated to form a pyrrole, thiophene or furan monomer substituted or not substituted at the R2 and / or R3 position. The monomer formed is polymerizable, and can polymerize via the R1 and R4 position. The groups R2 and R3 can be the same or different. The groups R2 and R3 can also both form part of a closed ring structure. A suitable example of such a precursor monomer is 3,4- (alkylene-vic-dioxy-) thiophene-2,5-dicarboxylic acid (see Tetrahedron 1967, vol. 23, p. 2137 ff.).

Other suitable precursor monomers with which an electrically conductive polymer can be prepared are precursor monomers having a structure according to formula (II), in which

X1 and X2 are the same or different and

to be; R1 and R2 are the same or different and are hydrogen or an alkyl group of 1-10 carbon atoms; R4 is hydrogen, or an alkyl, aryl or alkoxy group.

For formula (II), reference is made to the formula sheet.

For example, the precursor monomers of formula (II) can be synthesized as described in J. Chem. Soc. Perkin Trans. I (1985), p. 1277-1284. Another suitable precursor monomer is 4-aminobenzoic acid (see P. Ruelle, 7-Chem. Soc. Perkin trans. II, 1953 (1986).

The method of the invention is not limited to the simultaneous use of precursor monomers of one kind. Combinations of all types of precursor monomers are possible. Optionally, precursor oligomers can also be used. The precursor monomers can be activated, for example, by a thermal or a photochemical treatment. Any precursor monomer can be used in the process according to the invention.

The precursor monomers are usually in a suitable solvent. The solvent is often selected from the group of water, aromatic compounds, such as, for example, benzene, toluene and xylene, alcohols, such as, for example, methanol and ethanol, hydrocarbons, such as, for example, pentane and hexane, ethers, such as, for example, dioxane, diethyl ether, ethyl methyl ether and tetrahydrofuran ketones, such as, for example, acetone, diethyl ketone and methyl ethyl ketone, halogenated compounds, such as, for example, CHCl 3, CH 2 Cl 2 and carbon tetrachloride, esters, such as, for example, ethyl formate and ethyl acetate, and compounds such as acetonitrile, nitromethane, dimethyl sulfoxide, dimethyl formamide, triethyl phosphate, dimethylacetate. A mixture of several solvents can also be used.

The reaction mixture contains a catalyst containing a strong oxidizing cation and a stability-promoting anion. For example, the strong oxidizing cation is selected from the group Fe3 +, 0s4 +, Mn4 +, Cr3 +, K +, Cu2 +, Ce4 + and (C6 h5) 3 C +. Preferably the strong oxidizing cation is Fe3 +. The stability-promoting anion is usually a conjugated base of a strong acid. For the purposes of this invention, stability-promoting anion is understood to mean the anion of a relatively large organic compound, such as, for example, an aryl sulfonate compound, an alkyl sulfonate compound, a carboxylate compound, an acetate compound or an acetonate compound. Preferably, the stability-promoting anion is an aryl sulfonate compound or an alkyl sulfonate compound, which is unsubstituted or substituted. Examples of such compounds are dodecylbenzene sulfonate, perfluorooctyl sulfonate, benzene sulfonate, ethylbenzene sulfonate, 2-naphthalene sulfonate, trifluoroacetate, perfluorobutyrate, methyl sulfonate, p-toluenesulfonate, 2,6-sulfonate sulfonate, trifluoronate, trifluoronate -talene disulfonate, dinonyl naphthalene sulfonate, 1,3-benzenedisulfonate and 2,4,5-trichlorobenzene sulfonate. If desired, a mixture of several of these compounds is used. Preferably p-toluenesulfonate is used as a stability-promoting anion. The catalyst is usually added in a molar ratio to the precursor monomer, which is between 1:10 and 10: 1. Preferably, this ratio is between 1: 3 and 3: 1.

In order to improve the electrically conductive properties of the electrically conductive polymer, the reaction mixture may also contain a second catalyst. The second catalyst is selected, for example, from the group of inorganic acids, such as, for example, hydrochloric acid, sulfuric acid, chlorosulfonic acid and nitric acid, Lewis acids, such as, for example, compounds containing positive ions of iron, aluminum, tin, titanium, zirkomium, chromium, manganese, cobalt, copper, molybdenum, tungsten, ruthenium, nickel, palladium and / or platinum, and a halogen, a sulfate and / or a nitrate. Other suitable catalysts are, for example, ozone, diazonium salts, organic oxides, such as, for example, benzoquinone, and persulfates, such as ammonium persulfate, sodium persulfate and potassium persulfate.

Ziegler-Natta catalysts and K2Cr207 are effective in certain polymerization reactions. Examples of well-working catalysts are FeCl3, K3Fe (CN) 6, FeBr3, FeCl3.6H20, Fe (NO3) 3.9H20, Cu (NO3) 2, Fe (C104) 3.9H20, CuCl2.2H20, CuS04, Fe2 (SO4) 3.5H20 and (C5H5) 2Fe + FeCl4-. If desired, a mixture of different catalysts can be used. In view of the particularly high level of the electrically conductive properties of the resulting electrically conductive polymer, the second catalyst preferably contains iron (III) chloride. The second catalyst is usually added in a molar ratio to the precursor monomer, which is between 1:10 and 10: 1. Preferably, this ratio is between 1: 3 and 3: 1.

In a special embodiment of the process according to the invention, the reaction mixture contains both a catalyst containing a strong oxidizing cation and a stability-promoting anion and a second catalyst, the molar ratio between the two catalysts being between 10: 1 and 1:10 . Preferably, the ratio between the catalyst containing a strong oxidizing cation and a stability-promoting anion and the second catalyst is 10: 1 and 1: 2, more preferably between 2: 1 and 1: 2.

If desired, the reaction mixture in the process according to the invention contains a matrix polymer. This makes the polymer composition finally produced extremely suitable for the production of molding compositions, such as, for example, granules, fibers or films. The matrix polymer can be selected within very wide limits. Depending on the requirements of the polymer composition, for example with regard to the mechanical properties, in principle any polymer can be selected. In view of the processability, thermoplastic polymers are preferred, but thermosetting polymers, such as resins and binders, are also very suitable as matrix polymer for certain applications. Suitable matrix polymers are, for example, polyvinyl chloride or copolymer of vinyl chloride and other vinyl monomers, polyvinylidene fluoride or copolymers of vinylidene fluoride and other vinyl monomers, polystyrene or copolymers of styrene and other monomers, such as, for example, maleic anhydride and maleimide, polyacrylate polymers of an acrylic polymers of an acrylate polyolefins, such as, for example, polyethylene, ultra high molecular weight polyethylene (UHMWPE) and polypropylene, polyvinyl acetate, polyvinyl alcohol, polyesters, such as, for example, polyethylene terephthalate and polybutylene terephthalate, polycarbonates, polyetherimides, polyimides, polytetrafluoroethylene, polyamides, polyamide imide polybutadiene rubbers, alkyd resins, polyurethanes, acrylate resins, and the like. If desired, a mixture of multiple polymers can be used as a matrix polymer. The desired weight ratio between the amount of matrix polymer and the amount of electrically conductive polymer in the polymer composition according to the invention is a result of the optimization between the various desired properties, for example the desired conductive properties on the one hand and the desired mechanical properties on the other. Higher concentrations of matrix polymer have an adverse effect on the conductivity in the final polymer composition, while lower concentrations of matrix polymer may have an adverse effect on the desired mechanical properties. The weight ratio between the amount of matrix polymer and the amount of electrically conductive polymer in the polymer composition of the invention can vary within wide limits. Usually this ratio is between 1:99 and 99: 1, preferably between 1:15 and 15: 1. The optimum concentration of the matrix polymer is determined to an important degree by the mnlekiml crewi rht and the degree of branching of the matrix polymer.

For example, in a suitable embodiment of the method according to the invention, a solution is made of precursor monomer, catalyst and buffer in a suitable solvent. If desired, a matrix polymer is added to the resulting solution. For this purpose, for example, a matrix polymer can be impregnated with the solution of precursor monomer, catalyst and buffer. It is also possible for the matrix polymer to dissolve in the solvent. The polymer composition can be heated or irradiated with a radiation source at a self-determined time, whereby deblocking of the precursor monomers takes place. The deblocking can take place, for example, immediately after the polymer composition has been formed, but this can also be waited for a later time. In general, this time will be chosen after final design. After the polymerization reaction, any catalyst residues and other low molecular weight components can be removed by extraction and / or evaporation. These methods are well known.

Depending on the electrically conductive polymer obtained, the electrically conductive properties can be improved by means of an (oxidative or reductive) doping step, using the known doping techniques and reagents. These are mentioned, for example, in the 'Handbook of conducting polymers' (T.A. Skotheim, Marcel Dekker Ine., New York, USA (1986)).

The specific conductivity is measured according to the so-called four-point method. This method is briefly described in EP-A-314311. A more detailed description can be found in H.H. Wieder, Laboratory Notes on Electrical and Galvanomagnetic Measurements, Elsevier, New York, 1979. Using this method, the specific conductivity is measured! σ = (L / A) * (1 / R), where σ = specific conductivity [S / cm], L = distance between the two inner electrodes [cm], R = resistance [Ohm], A * cross-sectional area [cm2] .

Optionally, up to 60% by weight of fillers and / or antioxidants can be added to the polymer composition, which is produced by the method according to the invention. Examples of fillers to be added are talc, fiber, pigments, kaolin, wollastonite and glass.

After shaping the polymer composition, any catalyst residues and other low molecular weight components can be removed by extraction and / or evaporation. These methods are well known.

Products obtained with the method according to the invention can be used in the most diverse areas. Exponents of this are the areas of coatings and EMI-shielding attributes. Other suitable applications are, for example, conductive films and foils.

The invention is illustrated by the following examples without being limited thereto.

Examples and comparative experiments Preparation method iron (il) (p-toluenesulfonate) 3 14.6 grams of FeCl3.6H20 (Merck company) was dissolved in 204 ml of demineralised water. This resulted in a clear solution with a dark yellow-orange color. To this solution was then added a solution of 6.5 grams of NaOH (Merck, pure) in 44 ml of demineralized water, with vigorous stirring. The resulting iron hydroxide was decanted, washed three times with demi water and filtered with a glass filter (20-40 µm, D3).

The iron hydroxide was dissolved in 102 ml of methanol. To this solution was added a solution of 29 grams of p-toluenesulfonic acid monohydrate (Merck) in 44 ml of methanol. This resulted in a black suspension. This suspension was heated with stirring at a temperature of 45 ° C for 2 hours, the precipitate dissolving almost completely. Then the resulting solution was filtered using filter paper.

The solvent was largely removed under reduced pressure with a rotary film evaporator at a temperature of 50 ° C. The resulting product was then dried in a vacuum oven at 50 ° C for 196 hours. The remaining orange-yellow powder was finally jacked and stored in a P205 (N2 atmosphere) exicator. The yield of iron (III) (p-toluene sulfonate) 3 was 29 grams.

Example I

A solution was made of 0.25 grams of pyrrole-2-carboxylic acid in 1.5 ml of tetrahydrofuran (solution A). A solution was also made of 1.48 grams of iron (III) (p-toluenesulfonate) 3 and 0.42 grams of iron (III) chloride in 2.5 ml of tetrahydrofuran (solution B). Both solutions were poured together at a temperature of 20 ° C, resulting in a dark solution. Then a porous PE film (2 * 4 cm2, thickness 47 µm, porosity 85%) was impregnated with this solution by immersing this film in it for 30 seconds.

The impregnated film was air dried for 15 minutes, then placed in an oven at a temperature of 110 ° C (nitrogen atmosphere) for 5 minutes. Polymerization to polypyrrole occurred. Finally, the film was extracted with acetone until the acetone remained colorless, then again with methanol.

The specific conductivity measured, σ0, was 0.2 S / cm.

example II

Example I was repeated except that a film of 47 µm thick was used and an oven temperature of 136 ° C. Polymerization to polypyrrole occurred. The measured specific conductivity, σΟ, was 0.3 S / cm.

Example III

A solution was made of 0.25 grams of pyrrole-2-carboxylic acid in 1.5 ml of tetrahydrofuran (solution A). A solution was also made of 0.74 grams of iron (III) (p-toluenesulfonate) 3 and 0.63 grams of iron (III) chloride in 2.5 ml of tetrahydrofuran (solution B). Both solutions were poured together at a temperature of 20 ° C, resulting in a dark solution. Then a porous PE film (2 * 4 cm 2, thickness 47 µm) was impregnated with this solution by immersing this film in it for 30 seconds.

The impregnated film was air dried for 15 minutes, then placed in an oven at a temperature of 136 ° C (nitrogen atmosphere) for 5 minutes. Polymerization to polypyrrole occurred. Finally, the film was extracted with acetone until the acetone remained colorless, then again with methanol.

The specific conductivity measured, σ0, was 0.2 S / cm.

Example IV

A solution was made of 0.25 grams of pyrrole-2-carboxylic acid in 1.5 ml of tetrahydrofuran (solution A). A solution was also made of 2.21 grams of iron (III) (p-toluenesulfonate) 3 and 0.21 grams of iron (III) chloride in 2.5 ml of tetrahydrofuran (solution B). Both solutions were heated at a temperature of Poured together at 20 ° C, creating a dark solution. Then a porous PE film (2 * 4 cm2, thickness 47 µm) was impregnated with this solution by immersing this film in it for 30 seconds.

The impregnated film was air dried for 15 minutes, then placed in an oven at a temperature of 136 ° C (nitrogen atmosphere) for 5 minutes. Polymerization to polypyrrole occurred. Finally, the film was extracted with acetone until the acetone remained colorless, then again with methanol.

The measured specific conductivity, σΟ, was 0.07 S / cm.

Example V

For the films obtained in Examples I, II, III and IV, the conductivity properties were measured by placing the films in an air-flowed oven for 24 hours, the temperature being 120 ° C. After this temperature treatment, the specific conductivity, σΐ, was measured again. The properties thus measured are listed in Table 1: film specific conductivity [S / cm] retention

_o0_al_al / aO

I 0.2 0.02 0.10 II 0.3 0.025 0.08 III 0.2 0.008 0.04 IV 0.07 0.008 0.11

Comparative experiment A

2.46 grams of iron (III) - (p-toluenesulfonate) 3 were dissolved in 7 ml of tetrahydrofuran at a temperature of 20 ° C. Then 250 mg of pyrrole was added to immediately form a black precipitate.

It can be seen from the examples that when the electrically conductive polymer is manufactured by the process according to the invention, both the electrically conductive properties and the stability of the electrically conductive properties are good. In comparative experiment A, a black precipitate is immediately formed, which is only processable as a powder.

Claims (14)

A method of manufacturing an electrically conductive polymer, wherein polymerizable monomer units polymerize in an reaction mixture to form an electrically conductive polymer in the presence of a catalyst containing a strong oxidizing cation and a stability-promoting anion, characterized in that the polymerizable monomer units are obtained by in situ activation of precursor monomers. Process according to claim 1, characterized in that the precursor monomer has a structure according to formula I, wherein X is -N-, -S- or -0-; H R 1 is hydrogen, -C (0) 0H, -C (0) C (0) 0H, -C (0) H, -SO 3 H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C (O) 0H, or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C (O) OH, or a halogen; R 4 is hydrogen, -C (0) 0H, -C (0) C (0) 0H, -C (0) H, -SO 3 H, -I or -Br; with the proviso that R1-R4 are not all hydrogen at the same time, and that R2 and R3 can both be part of a closed ring structure. Process according to claim 1 or 2, characterized in that the precursor monomer is pyrrole-2-carboxylic acid. 4. Process according to any one of claims 1-3, characterized in that the strongly oxidizing cation is Fe3 +. Process according to any one of claims 1 to 4, characterized in that the stability-promoting anion is an unsubstituted or substituted aryl or alkyl sulfonate compound. Process according to any one of claims 1 to 5, characterized in that the stability-promoting anion is p-toluene sulfonate. Process according to any one of claims 1-6, characterized in that the molar ratio between catalyst and precursor monomer is between 1: 3 and 3: 1. 8. Process according to any one of claims 1-7, characterized in that the reaction mixture also contains a second catalyst. Process according to claim 8, characterized in that the second catalyst contains iron (III) chloride. Process according to claim 8 or 9, characterized in that the molar ratio between the second catalyst and precursor monomer is between 1: 3 and 3: 1. Process according to any one of claims 8-10, characterized in that the molar ratio between the catalyst containing a strong oxidizing cation and a stability-promoting anion and the second catalyst is between 10: 1 and 1: 2. 12. Process according to any one of claims 8-11, characterized in that the molar ratio between the catalyst containing a strong oxidizing cation and a stability-promoting anion and the second catalyst is between 2: 1 and 1: 2. Process according to any one of claims 1-12, characterized in that the reaction mixture also contains a matrix polymer. 14. Method as substantially described and illustrated by the examples.