METHOD FOR THE PREPARATION OF A POLYMER COMPOSITION CONTAINING AN ELECTRICALLY CONDUCTIVE POLYMER

Abstract: The invention relates to a method for the preparation of a polymer composition containing an electrically conductive polymer which is formed, in the presence of a catalyst, from polymerisable monomer units that are converted from non-polymerisable precursor monomers with the aid of a light source. The characteristic of the method according to the invention is that the precursor monomers have a structure according to formula (I), where X is (a), -S- or -O-; R1 is hydrogen, -C(O)OH, -C(O)C(O)OH, -SO3H, -C(O)H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(O)OH or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(O)OH or a halogen; R4 is hydrogen, -C(O)OH, -C(O)C(O)OH, -SO3H, -C(O)H, -I or -Br; it being understood that R1 and R4 must not be hydrogen at the same time and that both R2 and R3 may form part of a closed ring structure. The method according to the invention makes it possible to very easily and rapidly prepare a polymer composition containing an electrically conductive polymer. Furthermore, the method according to the invention permits a polymer composition to be produced that contains an electrically conductive polymer in specifically selected areas.

Description: METHOD FOR THE PREPARATION OF A POLYMER COMPOSITION CONTAINING AN ELECTRICALLY CONDUCTIVE POLYMER The invention relates to a method for the preparation of a polymer composition containing an electrically conductive polymer, comprising the steps of converting a non-polymerisable precursor monomer into a polymerisable monomer with the aid of a light source. A similar method is disclosed in JP-A-03-24120. According to the method described therein, a polymer composition containing non-polymerisable N-paratolyl substituted precursor monomers is exposed to a radiation source, as a result of which the precursor monomers are converted into polymerisable monomer units. This polymer composition is subsequently contacted with a suitable catalyst so that the polymerisable monomer units polymerise to form an electrically conductive polymer. This process yields a polymer composition with good electrically conducting properties and good stability of the electrically conducting properties. The conversion of the precursor monomers taught by the JP-reference to the corresponding monomers is a very slow process. Irradiation times of hours appear to be required. As a consequence a catalyst must not be present in the composition during the conversion step since every monomer unit formed is oxidized immediately by the usual catalysts. Due to the slow conversion only a limited amount of monomers comes available at every moment and thus the oxidised monomer units would fail to find sufficient othe rmonomer units to react with. The monomers then enter into side-reactions or at best, be able only to form short polymer chains, whereas short chains show only poor conductive properties. In adding the catalyst afterwards, again due to the immediate reaction between monomer and catalyst, the problem arises to apply the catalyst homogeneously throughout the composition and a polymer layer on the surface of the composition is formed thus obstructing the transport of the catalyst to the inside. Thus a need exist for a process in which the catalyst can be added and homogeneously mixed with the precursor monomers before the conversion is started. In consequence, a polymer composition containing an electrically conductive polymer following the method of JP-A-03-24120 can be prepared only through a time-consuming process consisting of a plurality of process steps. Thus, because of the time it takes, the known method offers limited possibilities of producing articles in an economically attractive manner. The present invention aims to provide a method that does not have the disadvantages set out above. This aim is according to the invention achieved in that during the conversion a catalyst is present and in that the precursor monomers have a molecular structure according to formula (I), where X is -N-, -S- or -0-; I H Rl is hydrogen, -C(0)OH, -C(0)C(0)OH, -S0 3 H, -C(0)H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)OH or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)OH or a halogen; R4 is hydrogen, -C(0)OH, -C(0)C(0)OH, -S0 3 H, -C(0)H, -I or -Br; it being understood that Rl and R4 must not be hydrogen at the same time and that both R2 and R3 may form part of a closed ring structure. For formula (I), refer to the formula sheet. In the method according to the invention, the catalyst may be added to the reaction mixture before the precursor monomers are converted into polymerisable monomer units, without any unwanted side-reactions taking place. Thus, the reaction mixture may contain a catalyst already before exposure. This makes it possible to very easily and rapidly prepare by the method according to the invention a polymer composition containing an electrically conductive polymer. Furthermore, the method according to the invention permits a polymer shaped article to be produced that contains an electrically conductive polymer in specifically selected areas. Thus, the method according to the invention may be employed to produce a polymer tide processing electrically conductive tracks. The obtained polymer composition, which contains an electrical] - conductive polyp r, may be used as, for instance, a (semi)conductive material, as electrode material and as a base material onto which an electrically conductive pattern is applied, such as printed circuit boards. Pre...rably, the precursor monomer is pyrrole-2-carboxylic acid. Synthesis of the precursor monomer is described in J. Am. Pharm. Assoc. 4_5_, 509 (1956). All combinations of X, Rl, R2, R3 and R4 are possible in the precursor monomer according to formula (I). The substituted (i.e. non-H) groups Rl and R4 may be eliminated thermally or photo-chemically with the formation of a pyrrole, thiophene or furan monomer whether or not substituted in the R2 and/or R3 positions. The former monomer is polymerisable and may polymerise via the Rl and R4 positions. The groups R2 and R3 . i be identical or different. Furthermore, the groups R2 and R3 may 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 f.f.). The catalyst to be used in the method according to the invention may be selected from, for instance, the group of inorganic acids such as hydrochlo: _ acid, sulphuric acid, chlorosulphonic acid and nitric acid, Lewis acids such as compounds containing positive ions of iron, aluminium, tin, titanium, zirconium, chromium, manganese, cobalt, copper, molybdenum, tungsten, ruthenium, nickel, palladium and/or platinum and a halogen, a sulphate, a nitrate, an arylsulphonate such as p-toluene sulphonate and p-dodecyl- benzene sulphonate and/or an acetyl acetonate. Other suitable catalysts are, for instance, ozone, diazonium salts, organic catalysts such as benzoquinone, and persulphates such as ammonium persulphate, sodium persulphate and potassium persulphate. Ziegler-Natta catalysts and K 2 Cr 2 0 7 are well effective in certain polymerisation reactions. Well effective catalysts include FeCl 3 , FeBr 3 , FeCl 3 .6H 2 0, CuCl 2 .2H 2 0, CuS0 4 , Fe(N0 3 ) 3 .9H 2 0, K 3 Fe(CN) 6 , Cu(N0 3 ) 2 , Fe(C10 4 ) 3 .9H 2 0, Fe 2 (S0 4 ) 3 .5H 2 0 and (C S H 5 ) 2 Fe + FeCl 4 - . A mixture of various catalysts may be applied if desired. Iron(III)chloride and copper(II)chloride are highly effective catalysts. The catalyst is normally added at a molar ratio to the precursor monomer of between 1:10 and 10:1 but preferably between 1:3 and 3:1. A matrix polymer may be combined with the polymer composition according to the invention if desired. To that end, a matrix polymer may be dissolved in, for instance, the polymer composition; alternatively, a shaped product consisting of the matrix polymer, for instance, may be impregnated with the polymer composition. Depending on the requirements for the polymer composition in terms of, for instance, its mechanical properties, any polymer may in principle be chosen as a matrix polymer. Thermoplastic polymers are to be preferred because of their processability, but thermosetting polymers for instance resins and binders are eminently suitable as matrix polymer for certain applications. Suitable matrix polymers are for instance polyvinyl chloride or copolymers 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 for instance maleic anhydride, maleimide, polyacrylates or copolymers of an acrylate with other monomers, polyvinyl carbazole, polyolefins for instance polyethene, ultra-high molecular polyethene (UHMWPE) and polypropene, polyvinyl acetate, polyvinyl alcohol, ethene-propene copolymers, ethene-propene-diene copolymers, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, polyetherimides, polyimides, polytetrafluoroethylene, polyamides, polyamide imides, polyethylene oxide, polybutadiene rubbers, alkyd resins, polyurethanes, acrylate resins and so forth. If desired, a mixture of several polymers may be used as matrix polymer. In a particular embodiment of the method according to the invention the reaction mixture is applied to a substrate in the form of, for instance, a coating, whereupon the precursor monomers become unblocked. The applied matrix polymer is preferably porous. The volume porosity of the applied matrix polymer is usually greater than 30% but preferably greater than 50% and more preferably greater than 65%. Suitable shaped products that may be applied are films, fibres, boards and other objects. Porous films containing a thermoplastic matrix polymer are described in, for instance, EP-A-105629, EP-A-309136, EP-A- 288021 and WO-A-86/02282. Films containing a polyolefin as matrix polymer are described in, for instance, EP-A-193318. Films containing an ultra-high molecular polyethene as matrix polymer are described in, for instance, EP-A-378279 and EP-A-163424. 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 consequence of the optimisation between the desired properties such as on the one hand the desired conducting properties and the desired mechanical properties on the other. High concentrations of matrix polymer have an adverse effect on the conductivity in the eventual polymer composition whereas low 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 according to the invention may vary widely. Usually, this ratio lies between 1:99 and 99:1 but preferably between 1:15 and 15:1. The various constituents needed to obtain the polymer composition according to the invention may be mixed by manners known to one skilled in the art. Methods are preferred by which the precursor monomers and the catalyst are dissolved in a suitable solvent, whereupon the matrix polymer is added if desired. The solvent is often chosen from the group formed by water, aromatic compounds for instance benzene, toluene and xylene, alcohols for instance methanol and ethanol, hydrocarbons for instance pentane and hexane, ethers such as dioxane, diethyl ether, ethyl methyl ether and tetrahydrofuran, ketones such as acetone, diethyl ketone and methyl ethyl ketone, halogenated compounds for instance CHC1 3 , CH 2 C1 2 and carbon tetrachloride, esters for instance ethyl formiate and ethyl acetate, and compounds for instance acetone nitrile, nitromethane, dimethyl sulphoxide, dimethyl formamide, triethyl phosphate, dimethyl acetamide and pyridine. Mixtures of solvents may be used also. Sometimes, the precursor monomer may be used as solvent. The non-polymerisable precursor monomers present in the polymer composition are converted into polymerisable monomer units by exposure to either a radiation source or a light source. Radiation sources that may be used in the method according to the invention emit radiation of sufficient power to convert the non-polymerisable precursor monomers into polymerisable monomer units. Lasers are especially suited as radiation source, but lamps such as IR lamps, UV lamps and visual light lamps are good alternatives. In a special embodiment sunlight is used. The polymer composition may be exposed to a fixed radiation source, during which process parts of the polymer composition may be covered, if desired, by a mask, or by a moving (marking) radiation source. If a focused radiation beam is desired, for instance when an electrically conductive track is to be marked, the emitted radiation can be focussed with the aid of a convergent system of lenses. If a wide radiation beam is desired, for instance when a mask is used, the emitted radiation can be spread with the aid of a divergent system of lenses. When a fixed radiation source is used, use is normally made of a high-power radiation source. When a moving, or marking, radiation source is used, use is normally made of a low-power radiation source. The marking speed at which the non- polymerisable precursor monomers present in the polymer composition are converted into polymerisable monomer units mostly lies between 5 and 300 mm/s, prefexably between 15 and 200 mm/s. Examples of suitable radiation sources are gas lasers such as C0 2 lasers, N 2 lasers, Excimer lasers, Argonion lasers, Kryptonion lasers, diode lasers, copper vapour lasers, titanium saffire lasers. Dye lasers and Neodymium Yttrium Aluminum Garnet lasers (Nd:YAG lasers). Suitable radiation sources may emit a continuous radiation beam, but a pulsating radiation beam may be used also. C0 2 lasers to be applied normally emit light with a wavelength of between 9 μm and 11 μm, preferably approximately 10.6 μm (infrared). Nd:YAG lasers to be applied emit light with a wavelength of 1064 nm; the frequency is preferably doubled so that the wavelength of the emitted light is 532 nm. The pulse frequency normally ranges from 1 Hz to 10 kHz but preferably from 3 to 6 kHz. The diameter of the parallel light beam is normally in the range between 0.01 and 0.5 mm but preferably between 0.02 and 0.15 mm. The applied current normally lies between 10 and 25 A but preferably between 10 and 18 A and even more preferably between 12 and 15 A. The energy density of the applied light beam normally lies between 0.10 kWatt/cm 2 and 1 Mwatt/cm 2 . Excimer lasers to be applied contain, for instance, Xenon fluoride gas or Xenon chloride gas, and emit light with a wavelength of, for instance, 351 nm or 308 nm. Argon lasers to be applied emit light with wavelengths of, for instance, 514.5 nm, 502 nm, 496.5 nm, 488 nm, 476.5 nm and/or 458 nm with a power of, for instance, 0.1 to 10 Watts. The preferred power is 1-5 Watts. Lasers whose operating parameters such as power and wavelength are well adjustable are to be preferred since these permit optimum adjustment to the particular method. After application of the method according to the invention, any catalyst residues and other low-molecular components may be removed by extraction and/or evaporation. If desired, non-exposed areas of the polymer composition may be removed in a similar fashion. The extraction methods are commonly known. If desired, the polymer composition according to the invention may contain up to 60 % by weight fillers and/or anti-oxidants. Examples of fillers are talc, reinforcing fibres, conductive fibres, light-absorbing additives, pigments, kaolin, wollastonite and glass. Depending on the precursor monomer used, the electrically conducting properties of the polymer composition may be enhanced by oxidative or reductive doping, in which process use may be made of the known doping techniques and doping reagents. These are mentioned in, for instance, the 'Handbook of conducting polymers' (T.A. Skotheim, Marcel Dekker Inc., New York, USA (1986)). The invention is elucidated by the following examples without being limited thereto. The conducting properties of the polymer composition in the examples given have been measured by the so-called two-terminal method. This method is described by H.H. Wieder in Laboratory Notes on Electrical and Galvanomagnetic Measurements, Elsevier, New York, 1979. This method is used for measuring the resistance. Example I A porous ultra-high molecular polyethene (UHMWPE) film of thickness 30 μm (length * width = 5 * 5 cm 2 ; volume porosity 85 %) was impregnated with a solution of 250 mg pyrrole-2-carboxylic acid and 700 mg FeCl 3 in tetrahydrofuran (THF). A mask was placed on this film. Subsequently, the film was exposed for 3 seconds to an Argonion laser (£ ectra Physics 2025 Argonion laser; all-lines mode; power 2 Watts) fitted with a r -/ergent lens. On beiϊig irradiated, an electrically conductive pattern corresponding with the mask appeared to have formed on the film. Thii pattern was dark-coloured. After extraction with acetone, the resistance was measured: 2500 ohms. The electrically conductive polymer had formed over the full thickness of the film. Examples II-V A porous ultra-high molecular polyethene (UHMWPE) film of thickness 30 μm (length * width = 5 x 5 cm 2 ; porosity 85 %) was impregnated with a solution of 250 mg pyrrole-2-carboxylic acid and 700 mg FeCl 3 in tetrahydrofuran (THF). Subsequently, the film so obtained was exposed to a marking Argonion laser (Spectra Physics 2025 Argonion laser; marking speed 1 cm/s; power 4.5 mW; continuous beam). The laser was adjusted to a particular wavelength: wavelength [nm] 514.5 496 488 476.5 During exposur the laser beam was focused to a diameter of approximately 30 μm. After exposure an electrically conductive track approximately 110 μm wide appeared to have formed on the film. The resistance measured after extraction with acetone was 30 kOhms. The electrically conductive polymer had formed over virtually the full thickness of the film. Example VI A porous ultra-high molecular polyethene (UHMWPE) film of thickness 30 μm (length * width = 5 * 5 cm 2 ; porosity 85 %) was impregnated with a solution of 250 mg pyrrole-2-carboxylic acid and 700 mg FeCl 3 in tetrahydrofuran (THF). Subsequently, the obtained film was exposed to a marking Nd:YAG laser (Haas laser Gretag 6411; polished, 2 SHG, Q-switched, wavelength 532 nm, marking speed 100 mm/s). After exposure, an electrically conductive track appeared to have formed on the film. The resistance measured after extraction with acetone was 200 kOhms. The electrically conductive polymer had formed at the surface of the film. Example VII A porous ultra-high molecular polyethene (UHMWPE) film of thickness 30 μm (length * width = 50 * 50 cm 2 ; porosity 85 %) was impregnated with a solution of 25 grammes pyrrole-2-carboxylic acid and 70 grammes FeCl 3 in tetrahydrofuran (THF). Subsequently, the obtained film was exposed to an IR lamp for 30 minutes. The resistance measured after extraction with acetone was 500 Ohms. Example VIII In 3.5 ml THF was dissolved 250 mg pyrrole-2-carboxylic acid and 700 mg FeCl 3 . To this solution was added 400 mg alkyd resin (high fatty acid content, viscosity 50 poise). The obtained mixture was applied as a coating onto a polyethylene terephthalate (PET) film. Subsequently, the coating was exposed to a marking Nd:YAG laser (Haas laser Gretag 6411; polished, 2 SHG, Q- switched, wavelength 532 nm, marking speed 100 mm/s). After exposure an electrically conductive track appeared to have formed on the film. The resistance measured after extraction with acetone was 150 kOhms. Comparative experiment A porous ultra-high molecular polyethene (UHMWPE) film of thickness 30 μm (length * width = 50 * 50 cm 2 ; porosity 85 %) was impregnated with a solution of 25 grammes pyrrole-2-carboxylic acid and 70 grammes FeCl 3 in tetrahydrofuran (THF). After drying, the film so impregnated was kept at a temperature of 20°C for 4 hours. Subsequently, the film was extracted with acetone. Analysis showed the acetone to completely contain the applied amounts of pyrrole-2- carboxylic acid FeCl 3 . The examples show that a polymer composition containing an electrically conductive polymer can be produced very rapidly so that the method may be practised in an economically attractive manner. The comparative experiment shows that in the method according to the invention the catalyst may be added to the reaction mixture already before exposure of the polymer composition without any undesirable side-reactions taking place.

Claims: C L A I M S 1. Method for the preparation of a polymer composition containing an electrically conductive polymer, comprising the steps of converting a non-polymerisable precursor monomer into a polymerisable monomer with the aid of a light source, characterised in that during the conversion a catalyst is present and in that the precursor monomers with the aid of a light source, characterised in that the precursor monomers have a structure according to formula (I), where X is -N-, -S- or -0-; I H Rl is hydrogen, -C(0)OH, -C(0)C(0)OH, -S0 3 H, -C(0)H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)OH or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)0H or a halogen; R4 is hydrogen, -C(0)OH, -C(0)C(0)OH, -S0 3 H, -C(0)H, -I or -Br; it being understood that Rl and R4 must not be hydrogen at the same time and that both R2 and R3 may form part of a closed ring structure. 2. Method according to Claim 1, characterised in that the precursor monomers are pyrrole-2-carboxylic acid. 3. Method according to Claim 1 or 2, characterised in that the polymer composition also contains a matrix polymer. 4. Method according to any one of Claims 1-3, characterised in that the polymer composition is exposed to a fixed light source, part of the polymer composition being covered by a mask. 5. Method according to Claim 4, characterised in that the light source is a gas laser. 6. Method according to any one of Claims 1-3, characterised in that the polymer composition is exposed to a moving light source. 7. Method according to Claim 6, characterised in that the light source is a pulsating laser or a continuous laser. 8. Method according to Claim 7, characterised in that the pulsating laser is a Neodymium Yttrium Aluminium Garnet laser, an Excimer laser, an Argonion laser or a Kryptonion laser. 9. Method according to any one of Claims 6-8, characterised in that the diameter of the light beam emitted by the light source lies between 0.01 and 0.5 mm. 10. Method according to any one of Claims 6-9, characterised in that the light source moves at a speed of 15-200 mm/s. 11. Method according to any one of Claims 1-10, characterised in that the polymer composition is doped on being exposed. 12. Composition containing precursor monomers having a molecular structure according to formula (I), where X is -N-, -S- or -0-; I H Rl is hydrogen, -C(0)0H, -C(0)C(0)0H, -S0 3 H, -C(0)H, -I or -Br; R2 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)OH or a halogen; R3 is hydrogen, an alkyl group (with 1-10 carbon atoms), -C(0)OH or a halogen; R4 is hydrogen, -C(0)OH, -C(0)C(0)OH, -S0 3 H, -C(0)H, -I or -Br; it being understood that Rl and R4 must not be hydrogen at the same time and that both R2 and R3 may form part of a closed ring structure. 13. Polymer composition containing electrically conductive tracks. 14. Method substantially as described and elucidated by the examples.

Inventors: SCHELLEKENS RONALD MICHAEL ALE, VAN DIJK HANS KLAAS, SCHELLEKENS, RONALD, MICHAEL, ALEXANDER, MARIA, VAN DIJK, HANS, KLAAS
Applicants: DSM NV, DSM N.V.
Application year: 1993
Main classification: G03F7
IPC codes: C08G61, C09D5, G03F7, H01B1