ELECTRICALLY CONDUCTIVE POLYTHIOPHENE AND PROCEDURE FOR ITS MANUFACTURING, AND ITS USE

Abstract: An electrically conductive polythiophene or substituted polythiophene, a procedure for its manufacturing and its use. The electrically conductive polythiophene or substituted polythiophene has been doped or treated with FeCl3 or with compounds containing FeCl4 anions. The electrically conductive polythiophene or substituted polythiophene is manufactured by treating it in a way known in itself in the art with a fluid containing salts which comprise FeCl3 or FeCl4 anions. The polythiophene is used as a positive electrode in an electro-chemical cell, as an electrically conductive film, powder or other product.

Description: Electrically cxraSuctive polythiophene and procedure for its manufacturing, and its use The present invention concerns an electrically conductive poly¬ thiophene polymer and a procedure for its manufacturing, and its use towards purposes in which electrical conductivity properties are required. Electrically active, or electrically ∞nductive, polymers can be produced from organic polymers having long chains of conjugated double bonds. The pi electrons in these double bonds can be "dis¬ turbed" fcy adding to the polymer certain doping agents which are either electron recipients or donors. Hereby vacancies, or extra electrons, are established in the polymer chain which enable elec¬ tric current to proceed along the conjugated chain. The electrical conductivity of the polymers can be regulated, in dependence of the doping agent content, so as to span virtually the entire cσn- ductivity range from insulators to metals. Electrically conductive polymers of this kind have numerous interesting practical appli¬ cations, such as in the manufacturing of light-weight batteries and storage batteries for instance. Polythicphene is one of those polymers which can be made electri¬ cally active in the manner just described. Polythiophene can be produced e.g. fcy using Ziegler-type catalysts and acid initiators. Another way to produce polythiophene, known in the art, has been disclosed e.g. in the EP Patents No. 95973 and 96612, and in the article: Kaneto et al., Japanese Journal of Applied Physics, Vol. 22, 1983, p. 1567-568. A xrding to the references, electrically active polythiophene film is manufactured fcy electrolytically polymerizing thiophene fcy an anodic oxidizing reaction in a cell wherein the electrolyte solution contains thiophene and an electro- lyte salt _nfo:__ming to the form MX, where M is an alkali metal, usually Li, or equally (04 ) 4 N + or (C^HS^NΓ 1" , and X is BF 4 ,C104, PFg, AsFg or CF3SO3. Both polymerisation of thiophene and its doping will then take place simultaneously. The electrical conduc¬ tivity of the fi-Lm is in the range of 0.1 to 100 Scm "1 , depending on the doping ion. It is possible, if desired, to remove doping ions from the films fcy electro-chemical or chemical reduction, whereby electrically non-conductive polythiophene fi_Lm is obtained. The conductivity of the reduced film is less than 10~ 8 Son" 1 . The usefulness of electrically active polymers depends, among other things on their stability characteristics. Polythiophene in reduced pure form is highly stable under various conditions, e.g. in air, humidity, vacuum and high temperatures. In contrast, the stability of electrically active polythicphene under different conditions is dependent on the doping ion that has been used. The polythiophene complexes announced in the references cited above are more or less unstable and, therefore, questionable in many applications. For instance, polythicphenes dcped with BF4, AsFg and PFg are exceedingly sensitive to humidity. Polythicphene doped with CIO4 presents good stability in air at normal temperature, but poor stability characteristics at elevated terrperatures, and in addition the dry complex is prone to be explosive. Same of the doping agents, again, command such high price that their use is not economical. The present invention concerns an electrically conductive polythio¬ phene polymer or substituted thicphene polymer which has excellent stability characteristics in air, humidity, vacuum and elevated terrperatures, as well as good electrical conductivity properties. The electrically conductive polythicphene or substituted polythio- phene of the invention is characterized in that it has been dcped, or treated, with FeCl.3 or with compounds containing FeCl 4 anions. The invention also concerns a procedure for manufacturing electri¬ cally cx∑ra-tuctive polythiophene, said procedure being characterized in that polythicphene or substituted polythicphene manufactured in a manner known in itself in the art is treated with FeCl.3 or with compounds which contain FeCI.4 anions. The invention also contains the use of polythicphene or substituted polythicphene doped with FeCI.3 or with ∞rrpσunds ∞nt-aining Feα.4 anions, in applications where electrical conductivity properties are required. The structure of the polythicphene or substituted polythiophene of the invention conforms to the equation (I) : where R lr and R 2 are either hydrogen atoms both or one or both may be an inorganic substituent such as Br, Cl, I, F, OH or CN or an organic substituent such as CH2CN, OCH3, CH 3 , C2H5 or C 6 H5, a is in the interval of 3-5, Y is in the interval of 0.0001-0.50 and X is greater than 4. In other words, the stoichiαrretric composition of the polythicphene of the invention conforms to the formula [(C 4 H 2 S) (FeCl a )γ χ, where a is in the interval of 3-5, Y is in the interval of 0.0001-0.50 and X is greater than 4. The electrically conductive polythicphene of the invention is usable as an electrically conductive film either as such as combined with another material. Thus, the film may be laminated to or applied as a coating on the surface of substrates consisting of other materials, such as plastics or metals, or between them. The poly¬ thiophene of the invention may equally be used in the shape of electrically conductive granules or powder, depending on the practi¬ cal application. In the procedure of the invention, polythicphene or substituted polythicphene maπufactured in any appropriate way is dcped or treated with Fed 3 or a substance containing FeCl.4 anions. Thus it is possible for iraπufacturing the starting material to use for instance the above-mentioned procedures for maπufacturing pure polythiophene. Then, in the above formula (I) either one or both of the substitueπts R^ and R 2 may be either an inorganic substituent such as Br, Cl, I, F, OH or CN or an organic substituent such as CH2C , OCH3, CH 3 , C 2 H 5 or Cg_ . Highly suitable polythicphenes are those in which the substituent is the CH3 group, such as poly(3- methylthicphene) and poly(3,4-dirrethylthiσphene) . It is also poss¬ ible to use polythicphene that has been dcped e.g. in other ways known in themselves in the art, if hereby desired effects are achieved. The doping of polythicphene or substituted polythiophene with Fea.3 or with substances contaiiiing Feca.4 anions may take place in various ways. One of the possibilities is to treat polythicphene with a fluid which contains FeCl 3 or cαπpounds containing FeCl 4 anions. Said cσrrpσunds may for instance be alkali salts such as Li eCl4 or nitrosyl salts such as N0FeCl 4 . The fluid may be a suitable organic solvent, e.g. nitrαπiethane, or any other solvent or suspension fluid which does not affect the doping process ad¬ versely. Usually, such organic solvents will be contemplated which dissolve the salt in question. For instance, aliphatic or aromatic hydrocarbons are appropriate. The film obtained upon doping is washed clean of extra dcping substance, using a suitable solvent, preferably the solvent that was used in the dcping proper, and the film is dried. It is possible by varying the dcping agent content, the dcping time and the tsirperature to regulate the electrical cαnductiviy properties of the dcped polythicphene. The concentration of the doping agent may as a rule vary within 10~ 5 M to saturation. The dcping process is more amenable to control when using dilute solutions. Dcping can be carried out under atmos¬ pheric pressure or in over-pressure or vacuum. Dcping in (partial) vacuum is well appropriate because in that case no high terrperatures are required. The lower and upper temperature limits are normally determined fcy the freezing point and boiling point of the solvent. The dcping time is selected, depending cn reagents, temperature and desired end result, to be from a few seconds to a few days. Polythicphene or substituted polythicphene according to the inven¬ tion may also be manufactured fcy treating polythicphene film or powder with FeCl 3 vapour. This vapour treatment may be carried out under normal pressure or using elevated pressure or vacuum. Vacuum treatment is to be rec πmended because in that case the maπufac- turing can be carried out at lower temperatures. A third procedure for manufacturing electrically conductive poly¬ thicphene according to the invention is to use polythiophene in the farm of a film or of powder as working electrode in an electro- chemical cell in which the electrolyte solution contains an Feα.4 salt in an organic solvent. The electrolyte solution may equally be a molten salt mix, for instance FeCl3/BuPyCl or equivalent. When an electric current is passed through the cell, the polythio¬ phene electrode is oxidized and the Fed 4 anion present in the electrolyte is dcped into the polymer film to achieve electric equilibrium. The electrically active polythicphene of the invention has good stability properties in various conditions, as will be apparent from the acxxaπpairying examples, in which the polythiσphenes of the invention, their manufacturing procedures and their properties are more closely described. In the examples, polythiophene was used which had been prepared as follows. Into a glass cell, in which had been placed a working electrode (a platinum foil) and a counter- electrode of alum_Lnium, was added electrolyte solution having the cαπposition: 0.5 M thicphene and 0.1 M T11 4 in a nitrobenzene benzonitrile solvent. The electrolyte solution was hereafter care¬ fully bubbled with argon gas for removal of oxygen. Polymerizing and dcping the thiophene took place either galvanostically or potentiostatically-by-polarizing the working electrode with a voltage of at least 4.6 V with reference to the counter-electrode. Growth of electrically active, BF4 aniαn-dcped polythicphene com¬ menced an the platinum electrode. Polymerizing time was 30 minutes, and the current density of the working electrode was 2 crr Hereby a polythiσphene-BF4 film was obtained, which had thickness about 10 um. The electrically conductive film was immediately on polymerizing electro-chemically reduced fcy reversing the polarity of the electrodes and setting the current density of the counter- electrode at 1 cm 2 . The time of electro-chemical reduction was 15-30 minutes. The partly reduced film was then detached from the platinum electrode and immersed in methanol over night. After this methanol treatment, the film was washed with boiling methanol and chloroform. The washed polythicphene film was dried at 100°C in dynamic vacuum over night. The result was a highly pure, FB 4 -free insulating polythicphene film having C, H and S total content higher than 99 % and the stoic-hicmetriσ cαrpositiσn: C 4.0 H 2.06 S 1.08* Infra-red spectrosccpy analyses revealed than the polythicphene that had been obtained was poly(2,5-thiαphene) . Example 1 A polythicphene film having ∞nductivity less than 10"" 8 Sαo" 1 and weight 2.28 mg was immersed in 0.1 M FeCl3-nitrαmethane solution. The dcping time was 30 minutes. After washing and drying, the weight of the film was 5.14 mg. This increase in weight corresponds to 23.5 mol% Fed.4, that is, the complex that had been obtained was Elemental analyses of a sample yielded the stoichiσmetric composition: con ~ ductivity of the film was measured by the four-point method, and it was 2.4 Scan" 1 . Example 2 A polythicphene film having weight 29.4 mg was immersed in 0.05 M FeC^-nitrcmethane solution. Hie dcping time was 60 minutes. After washing and drying, the weight of the film was 47.6 mg, corres¬ ponding to [C4H2S(FeCl4) 0 .26-'x* T e conductivity of the film was 18.6 Scm" 1 . Example 3 A polythicphene film having the weight 15.01 mg was immersed in 0.005 M FeC^-nitrαmethane solution. The dcping time was 5 minutes. After washing and drying, the weight of the film was 15.26 mg, and its conductivity was 3.7 x 10~ 3 Scm" 1 . The composition of the film was dete__mined and found to be c4H2S(FeCl4) o.oθ6^ * Example 4 Polythicphene films were dcped as in Examples 1-3 with FeCl 3 , using various FeCl 3 contents. The electrical conductivity of the film thus obtained was measured fcy the four-point method. In Fig. 1 are shewn the electrical conductivities of the films, with varying dcping agent content Y. The figure reveals the steep ascent of electrical conductivity at very low dcping agent contents and its slower increase at higher contents, where the conductivity is also higher. Example 5 A polythicphene film having conductivity less than 10~ 8 Scm" 1 was affixed to four platinum electrodes in a glass reactor. The reactor was evacuated and FeCl 3 vapour was evaporated over the film. During dcping, the conc5_uctivity of the film was measured, its value in¬ creasing within a few minutes up to 10" 2 Scm" 1 . After 24-hσur doping the conductivity of the film was 8.6 Scm -1 . Example 6 A polythicphene film was attached to a platinum electrode and the electrode immersed in an electro--chemicar ~ glass cell in which an alum_Lnium foil served as counter-electrode. The polythicphene electrode was polarized with +4.2 V voltage with reference to the cca_nter^-electrode. After one hour's potentiostatiσ reaction the film was washed and dried. The conductivity of the film was 24 Scm" 1 . Example 7 A poly(3-_rethylthicphene) film having conductivity less than 10~ 8 Scm" 1 and weight 4.09 mg was __mmersed in 0.05 M FeCl3 solution. Dcping time was 30 minutes. After washing and drying the weight was 6.25 mg and ∞ndt_ctivity 56.1 Scm" 1 . The composition of the film was determined and found to be In the examples following next, that stability properties of poly- thicphene-FeCl4 films in different conditions were determined. The initial conductivity of these films at roam temperature was between 1 and 20 Scm" 1 . Example 8 A polythicphene-FeCl4 film having conductivity 10 Scm" 1 was affixed to four platinum electrodes. The conductivity of the film was continuously observed. The film kept 4 months in a laboratory ataaosphere had conductivity 7.6 Scm" 1 . In Fig. 2 is plotted the change of electrical cc auctivity as a function of time, as well as the conductivities of equivalent, S10 4 - and BF 4 -dσped films. The conductivity has been plotted in terms of relative conductivity, meaning the ratio of the absolute conductivity measured and the conductivity at roam temperature at the start of experiment. The polythiophene film dcped with BF 4 has clearly poorer stability characteristics than the film of the invention. Example 9 A polythiophen -FeCl4 film having conductivity at roam temperature 1.6 Scm" 1 was attached to four platinum electrodes in a glass reactor. The reactor was continuously evacuated and its temperature maintained at 100°C. The reactor was kept under dynamic vacuum for 24 hours, during which time the conductivity of the film increased and levelled out at 3.5 Scm "1 . When the specimen had been cooled to roam temperature, its conductivity was 2.3 Scm" 1 . The experiment was repeated so that the film was kept at 150°C in dynamtic vacuum for 24 hours. Fig. 3 shows the (relative) behaviour of the conduc¬ tivity of films at elevated temperatures in dynamic vacuum. Example 10 A polythiσphene-C104 film having conductivity at roam temperature 2 Scm "1 was attached to four platinum electrodes in a glass reactor. The reactor was continuously evacuated. The conductivity of the polythiophene-C104 film was observed while the film was kept at elevated temperature in dynamic vacuum. Fig. 4 reveals the poor characteristics of this complex at higher temperatures. Example 11 A polythicphene-FeCl4 film having conductivity at roam temperature 10 Scm" 1 was attached to four platinum wires in a glass reactor. The reactor teamperature was raised to 150°C. Pure, dry oxygen was blown past the film for 24 hours. The conductivity of the film remained almost unchanged, i.e., its conductivity after 24-hσur oxygen treatment was 9.6 Scm "1 at roam temperature. Example 12 A polyt_hicphene-FeCl 4 film having conductivity at roam temperature 4.3 Scm" 1 was attached to four platinum wires in a glass reactor. The reactor was kept at roam temperature. The film in the reactor was flushed with H2θsaturated oxygen for 24 hours. The conductivity of " the film hereby went down to " 0.74 Scm" 1 . The film was t _&n - dried at 100°C for 24 hours, whereafter the film was cooled to roam temperature. Its conductivity had gone up to 1.2 Scm" 1 . Example 13 A polythiophene-BF4 film having conductivity at roam terrperature 20 Scm" 1 was kept in laboratory atmosphere at different humidities. Fig. 5 reveals the poor resistance of the film to humidity.

Claims: Claims 1. Electrically ∞nductive polythicphene or substituted polythio¬ phene, characterized in that it has been doped or treated with FeCl3 or with cxmpounds conteining FeCl 4 anions. 2. Polythicphene or substituted polythicphene according to claim 1, characterized in that its structure conforms to the formula (I): where R j _ and R2 either both are hydrogen atoms or one or both are an inorganic substituent such as Br, Cl, I, F, CH or CN or an organic substituent such as CH 2 CN, 0013, CH 3 , C 2 H 5 or CHs, a = 3- 5, Y = 0.0001-0.50 and X > 4. 3. Polythicphene or substituted polythicphene according to claim 1 or 2, characterized in that the stoichiαmetric structure corresponds to the formula -.(C 4 H2S(FeCl a )yl x , where a = 3-5, y is in the inter¬ val 0.0001-0.50 and x is greater than 4. 4. Polythicphene or substituted polythicphene according to any one of claims 1-3, characterized in that its electrical conductivity is in the range of 10 "10 to 500 Scm" 1 . 5. Polythiophene or substituted polythicphene according to any one of claims 1-4, characterized in that it is in the form of a film or p<-wder. 6. Procedure for manufacturing electrically active polythicphene or substituted polythicphene, characterized in that polythicphene or substituted polythicphene manufactured in a way known in itself in the art is treated with FeCl 3 or with a compound containing FeCl4 anions. 7. Procedure a«x>rding to claim 6, characterized in that polythio¬ phene or substituted polythicphene manufactured in a way known in itself in the art is treated with a fluid cor±aining FeCl 3 or salts containing Feca.4 anions. 8. Procedure according to claim 6, characterized in that FeCl 3 is evaporated onto polythicphene or substituted polythicphene present in film or powder form. 9. The use of a film according to any one of claims 1-5 containing polythicphene or substituted polythicphene, as a positive electrode in an electro-chemical cell in which the electrolyte contains an Feca.4 salt, whereby one obtains polythicphene or substituted poly- thicphene dcped with FeCl 4 anions. 10. The use of polythicphene or modified polythicphene according to any one of claims 1-5 which has been dcped or treated with substances containing FeCl 3 or Feca.4 anions, as an electrically conductive film, powder or other product.

Inventors: KARJALAINEN SARI, MONONEN PIRJO, OESTERHOLM JAN-ERIK, KARJALAINEN, SARI, MONONEN, PIRJO, OESTERHOLM, JAN-ERIK
Applicants: NESTE OY
Application year: 1986
Main classification: H01B1
IPC codes: C08G61, C22B11, H01B1, H01M4