EP0981568A1 - Conductive polymers and processes for their preparation - Google Patents
Conductive polymers and processes for their preparationInfo
- Publication number
- EP0981568A1 EP0981568A1 EP97907222A EP97907222A EP0981568A1 EP 0981568 A1 EP0981568 A1 EP 0981568A1 EP 97907222 A EP97907222 A EP 97907222A EP 97907222 A EP97907222 A EP 97907222A EP 0981568 A1 EP0981568 A1 EP 0981568A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- nickel
- polymer
- cobalt
- compound
- conductivity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G61/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
- C08G61/12—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule
- C08G61/122—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides
- C08G61/123—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds
Definitions
- This invention relates to conductive polymers and to processes for their preparation.
- Known conductive polymers include poly (heteroaromatic) compounds prepared by oxidative polymerisation in the presence of transition metal compounds.
- the metal compounds have been reduced to metallic islands.
- metal-containing anions increase conductivity by acting as dopants. Other mechanisms may also be at work.
- An important point is that in each case the polymer relies on the continued presence of the transition metal species for conductivity.
- the transition metal species is permanently bound into the polymer to the extent that it cannot be removed. In others it can be removed, by washing, but the conductivity of the polymer drops in line with removal of the transition metal species.
- conductive poly (heteroaromatic) compounds which process employs transition metal compounds.
- An ordered polymer may be produced by the process, which means that charge carrier mobility is high. Dopants are thus particularly effective in bringing about conductivity enhancement, and a polymer of very high conductivity may be produced.
- a polymer prepared by a process of the invention is believed to have a more ordered structure than a corresponding polymer prepared in the absence of a said compound of nickel (II) or cobalt (II) , and this is thought to be the reason for the greater conductivity.
- the presence of the nickel or cobalt compound during the polymerisation is responsible for enhanced conductivity (even through it may subsequently be removed from the polymer) , at least when doped by a suitable dopant, and preferably also when undoped.
- nickel (II) and cobalt (II) species are removable from the polymer formed but need not necessarily be removed. It may be acceptable to leave them in the polymer. In embodiments in which they are removed, their residual level in the polymer is then suitably no more than 100 ppmw, preferably no more than 20 ppmw, and most preferably no more than 10 ppmw. Thorough washing e.g. by Soxhlet extraction may give removal down to a content of a few ppmw. Complete removal may be achieved by use of a complexing agent such as EDTA.
- a conductive polymer as defined herein suitably has intrinsic conductivity of at least lxlO "2 Sm "1 , and this in itself is likely to be higher by a factor of at least 10 than that of a corresponding polymer prepared in the absence of said nickel or cobalt compound.
- intrinsic conductivity we mean conductivity of a sample of the polymer which has a content of nickel (II) or cobalt (II) species in the range 0-100 ppmw, and no dopant, such as other transition metal species, or iodine. This level of conductivity means that a polymer in accordance with the present invention may find use e.g. as an anti-static coating even in the absence of any dopant.
- polymers in accordance with the invention contain a dopant.
- the conductivity of such a doped polymer is at least 1,000 Sm "1 , preferably at least 5,000 Sm "1 , most preferably at least 15,000 Sm "1 .
- Conductivities in excess of 50,000 Sm "1 are achievable in preferred embodiments. Such conductivities may be achieved even when the nickel or cobalt species are removed.
- any dopants conventionally used in the art may be employed. Iodine is a convenient dopant, primarily for laboratory assessment.
- suitable dopants are fluoroborate, toluene sulphonate, trifluoromethane sulphonate and perchlorate species.
- suitable dopants may include transition metal oxidants such as FeCl 3 , and arsenic pentafluoride and antimony pentafluoride .
- the process is such that the presence of said compound of nickel (II) or cobalt (II) dissolved in the reaction mixture brings about a polymer of significantly higher molecular weight, (preferably at least double, whether assessed as weight average molecular weight or number average molecular weight) than that of a polymer prepared under identical conditions, but in the absence of said compound of nickel (II) or cobalt (II) .
- the heteroaromatic monomer compound used in the process of the invention may be an asymmetric compound which can polymerise in one of two (or more) orientations.
- the process is such that the presence of said compound of nickel (II) or cobalt (II) brings about a polymer of higher regioregularity than that of a polymer prepared under identical conditions, but in the absence of said compound of nickel (II) or cobalt (II) ; preferably the incidence of regioregular couplings is at least 10% higher, preferably at least 20% higher.
- the heteroaromatic monomer compound used in the process of the invention is a compound of general formula
- R 1 and R 2 independently represent a hydrogen atom, or an optionally substituted alkyl group, or an optionally substituted alkoxy group, or R 1 and R 2 together represent an optionally substituted butylene chain or a chain of formula -O-Q-O- wherein Q represents an optionally substituted ethylene chain.
- R 1 and R 2 may be such that the compound is asymmetric about the hetero atom X.
- An optional substituent of an alkyl, alkoxy or alkylene group suitably includes halogen, especially fluorine, chlorine or bromine atoms, and nitro, cyano, hydroxyl, C M alkoxy, C haloalkoxy, (C M alkoxy) carbonyl, amino and C alkylamino groups. It is preferred, however, that alkyl, alkoxy or alkylene groups are unsubstituted.
- An optionally substituted alkyl or alkoxy group R 1 and/or R 2 suitably has 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, most preferably 1 to 8 carbon atoms.
- Any such group having more than 3 carbon atoms may be branched but is preferably linear.
- R 1 and R 2 represent independent moieties, rather than a chain. Those independent moieties may differ from each other, in preferred embodiments.
- R 1 and R 2 independently represent a hydrogen atom or an alkyl group.
- R 1 represents an alkyl group.
- R 2 represents a hydrogen atom.
- the moiety X preferably represents an N-H group or a sulphur atom, most preferably a sulphur atom.
- Any nickel (II) or cobalt (II) compound which dissolves in the reaction mixture may be employed.
- Suitable organic salts may, for example, be sulphonates, for examples toluene sulphonate and trifluoromethane sulphonate.
- inorganic salts are preferred, especially the chlorides and perchlorates.
- the reaction mixture preferably comprises an organic solvent and a small amount, suitably no more than 2% wt, and most preferably substantially no, water.
- organic solvents may be employed and the choice of a solvent for the particular process is well within the compass of the person skilled in the art, using his ordinary skill and knowledge. Solvent optimisation may be achieved by the ordinary process of trial and error. However, by way of guidance, we can state that polar aprotic solvents e.g.
- propylene carbonate, ethylene carbonate and acetonitrile are suitable for electrochemical processes in accordance with the invention, and halogenated hydrocarbon solvents, for example C, ⁇ chloroalkanes, or nitromethane or nitrobenzene are suitable for non-electrochemical processes.
- halogenated hydrocarbon solvents for example C, ⁇ chloroalkanes, or nitromethane or nitrobenzene are suitable for non-electrochemical processes.
- amine, alcohol and ether solvents are preferably not used either for electrochemical or chemical processes.
- the temperature for the reaction is a matter of choice but most such reactions are best carried out at relatively low temperature, for example -20 to 50°C, preferably 0 to 40°C, to assist in the formation of an ordered polymer structure.
- the concentration of the heteroaromatic monomer compound in the reaction mixture may suitably be in the range 0.01 to 2 M, preferably 0.05 to 1 M, most preferably 0.1 to 0.3 M.
- the concentration of the compound of nickel (II) or cobalt (II) in the reaction mixture may vary particularly widely, suitably being in the range 0.0001 to 2 M, preferably 0.001 to 1. Electrochemical processes may require relatively lower concentrations, for example 0.0001 to 0.1 M, preferably 0.001 to 0.01 M. Non- electrochemical process may require relatively higher concentrations, for example 0.01 to 2 M, preferably 0.05 to 0.5 M.
- the relative proportions of the heteroaromatic monomer compound (A) and the compound (B) of nickel (II) or cobalt (II) may vary very widely, for example within the molar range 1000:1 - 1:100 (A:B) , preferably 200:1 - 1:10.
- electrochemical processes may require higher proportions of heteroaromatic monomer compound to the compound of nickel (II) or cobalt (II) , for example within the molar range 1000:1 -10:1, preferably 200:1 - 20:1, and non-electrochemical processes may require lower proportions of heteroaromatic monomer compound to the compound of nickel (II) or cobalt (II) , for example within the molar range 100:1 - 1:10, preferably 20:1 - 1:5.
- Nickel and cobalt compounds may be used separately or together in processes of the invention and the above definitions relate to their combined amount, in embodiments in which they are used together.
- nickel (II) or cobalt (II) compounds used in the process of the invention dissolve in the reaction mixture to form Ni 2+ or Co + cations, and that these act as non-oxidising cations which do not initiate the polymerisation reaction, but which serve to catalyse or otherwise favour the formation of a more ordered polymer structure, and a polymer of higher molecular weight (perhaps by weak temporary complexation with the hetero atom) than would be achieved under corresponding conditions without the presence of the Ni 2+ or Co 2+ cations, and this is the cause of enhanced conductivity.
- the invention extends to a polymer made by a process in accordance with the present invention.
- a polymer is believed to be inherently new by virtue of its properties and not just by virtue of the process by which it is made and so in a further aspect the present invention provides a conductive polymer prepared by oxidative polymerisation of a heteroaromatic monomer compound, characterised by a conductivity when doped of at least 1000 Sm "1 (preferably at least 5000 Sm "1 , most preferably at least 15000 Sm "1 ) and a content of nickel (II) or cobalt (II) species in the range of 0-100 ppmw (preferably 0-20 ppmw, most preferably 0-10 ppmw) ; or a content of nickel or cobalt species in excess of 100 ppmw but which can be lowered to the range 0-100 ppmw (preferably 0-20 ppmw, most preferably 0-10 ppmw) with retention of conductivity when doped of at least 1000 S
- the number average molecular weight of the polymer is at least 10,000, most preferably at least 20,000.
- the weight average molecular weight of the polymer is at least 60,000, most preferably at least 100,000.
- the polymer contains no transition metal species, other than, optionally, the nickel (II) or cobalt (II) species.
- the proportion of identical couplings of monomers is preferably at least 65%, preferably at least 75%.
- the novel polymer is preferably a polythiophene, most preferably a poly (3-alkylthiophene) .
- Polymers described herein may find application as antistatic coatings for plastics products, but the conductivity is sufficiently high when doped that they may also be used as conductors in electronic circuits and devices, for example in printed circuit boards. Further applications include electromagnetic radiation shielding and electric wires and cables, with the polymer as an intermediate conductive interlayer between the conductor and the insulator. These may be wires and cables in which an insulating sheath surrounds a metallic core conductor. These may also be wires and cables, for example high tension power cables or other coaxial cables, in which the conductive layer is an outer sheath, around an insulator core. Used as an intermediate layer between the conductive sheath and the insulator core a conductive polymer of the invention will act as a field-smoothing layer.
- Polymers described herein may find application as such or may in known manner be blended or compounded with other polymers to obtain polymers with properties optimised for selected applications.
- 3-Methylthiophene (0.2 M) and dried tetraethyl- ammonium tetrafluoroborate (0.03 M) were dissolved in dry propylene carbonate.
- the solution was placed in a single compartment cell, and purged with nitrogen gas for 10 minutes.
- an indium-tin oxide anode, and a platinum cathode it was then electrolysed at 5°C in a manner well known in the art, at a constant current density of 14 mA cm 2 .
- the resulting black, shiny film on the anode had a conductivity of 7700 Sm "1 .
- Polymer films grown under identical conditions, but in the presence of 0.003 M of Ni(C10 4 ) 2 dissolved in the electrolyte had a typical conductivity of 21,000 Sm "1 .
- the polymer dopant was fluoroborate ions.
- the conductivity was 4000 Sm "1 after iodine doping; however, films of polymer synthesised under identical conditions except for the additional presence of 0.1 M of anhydrous NiCl 2 exhibited a conductivity of 38,000 Sm "1 when doped.
- Chemical analysis of the pure polymers showed that both materials could fairly be described as poly (3-hexyl-2 , 5- thiophenediyl) ; however, detailed examination of their nuclear magnetic resonance spectra and molecular weight distributions revealed a possible explanation for the difference in their properties.
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/GB1997/000742 WO1998041555A1 (en) | 1997-03-18 | 1997-03-18 | Conductive polymers and processes for their preparation |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0981568A1 true EP0981568A1 (en) | 2000-03-01 |
Family
ID=10806010
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97907222A Withdrawn EP0981568A1 (en) | 1997-03-18 | 1997-03-18 | Conductive polymers and processes for their preparation |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0981568A1 (en) |
JP (1) | JP2001516381A (en) |
AU (1) | AU1936197A (en) |
CA (1) | CA2284536A1 (en) |
WO (1) | WO1998041555A1 (en) |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3325892A1 (en) * | 1983-07-19 | 1985-01-31 | Basf Ag, 6700 Ludwigshafen | METHOD FOR PRODUCING FINE-PART ELECTRICALLY CONDUCTIVE PYRROL POLYMERISATS |
US5151224A (en) * | 1988-05-05 | 1992-09-29 | Osaka Gas Company, Ltd. | Tetrasulfonated metal phthalocyanine doped electrically conducting electrochromic poly(dithiophene) polymers |
-
1997
- 1997-03-18 WO PCT/GB1997/000742 patent/WO1998041555A1/en not_active Application Discontinuation
- 1997-03-18 JP JP54021298A patent/JP2001516381A/en active Pending
- 1997-03-18 AU AU19361/97A patent/AU1936197A/en not_active Abandoned
- 1997-03-18 EP EP97907222A patent/EP0981568A1/en not_active Withdrawn
- 1997-03-18 CA CA002284536A patent/CA2284536A1/en not_active Abandoned
Non-Patent Citations (1)
Title |
---|
See references of WO9841555A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO1998041555A1 (en) | 1998-09-24 |
CA2284536A1 (en) | 1998-09-24 |
AU1936197A (en) | 1998-10-12 |
JP2001516381A (en) | 2001-09-25 |
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