CA2622275A1

CA2622275A1 - Conductive polymers

Info

Publication number: CA2622275A1
Application number: CA002622275A
Authority: CA
Inventors: Ian David Brotherston; John Lindley Bancroft
Original assignee: Individual
Current assignee: Ionic Polymer Solutions Ltd
Priority date: 2005-09-17
Filing date: 2006-09-18
Publication date: 2007-03-22
Also published as: GB0519045D0; GB2430439B; GB2430439A; WO2007031781B1; GB0618289D0; WO2007031781A1; JP2009509294A; EP1934286A1; KR20080064947A; CN101273092A

Abstract

There is provided a solid ionically conductive polymer having repeat units of a quaternary amine and including a plasticiser in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.

Description

Conductive Polymers This invention relates to solid ionically conductive polymers, structures and fuel cells incorporating same, and associated methods of production and use.

There is much interest in the manufacture and use of conductive polymers. A wide range of ionically conductive polymers are known, with possibly the most famous example being Nafion (RTM). Nafion (RTM) is a conductive membrane that conducts via cation conduction. Whilst Nafion (RTM) has achieved significant commercial success, there are problems associated with the material. In particular, Nafion (RTM) can only achieve useful conductivities in a swollen, hydrated state in which the material achieves volumes approximately 10 times greater than the volume associated with its unhydrated state. Thus, Nafion (RTM) membranes require constant hydration in order to function as conductive membranes and cannot operate conductively at high temperatures, eg, at greater than 100 C.

International publications W000/06610, W000/06533, W000/06658, W001/36510, WO01/40874 and WO01/74919, the contents of all of which are herein incorporated by reference, disclose a class of polymers obtained from the polymerisation of a number of compounds which possess one or more dienyl end groups. The polymers possess or promise a variety of useful and exciting properties, one of which was thought to be conductivity. However, further investigations have revealed that the conductivities of the polymers disclosed in these documents are not optimal ones. In fact, the present inventors have found that large increases in the conductivities of various polymers including polymers of the type generically disclosed in the above mentioned International publications is possible.

Accordingly, the present invention, in at least some of its embodiments, provides improvements to the prior art conductive polymers discussed above.
Furthermore, the present invention can provide advantageous ways of applying conductive polymers and provides a class of conductive polymers that conduct by anionic conduction.

According to a first aspect of the invention there is provided a solid ionically conductive polymer having repeat units of a quaternary amine and including a plasticiser in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.

Conductivities comparable to that of Nafion (RTM) can be achieved without requiring hydration. Without wishing to be bound by any theory, it is believed that departure from crystallinity increases the efficiency of ion transfer between repeat units.

The plasticiser may be present as an additive to the polymer. A preferred plasticiser of this sort is propylene carbonate. The polymer may contain between 5 and 60% by weight plasticiser additive. In order to produce polymers with reasonable mechanical strength, it is preferred that the polymer contains between 5 and 30% by weight plasticiser additive. For higher conductivities, the polymer may contain between 25 and 60% by weight plasticiser additive. In general,.polymers of this type exhibit somewhat poorer mechanical properties, but this may be acceptable or even desirable in certain applications. In some instances the polymer may contain more than 60% by weight plastic additive.

Alternatively the polymer may be self-plasticising. The polymer can be self-plasticising in numerous ways. This polymer may include an anion present as a counterion to the quaternary amine, and the anion may act as a plasticiser. In alternative embodiments the quaternary amine itself acts as a self-plasticiser. In general larger anions and/or cationic quaternary amines render the polymer less likely to adopt a crystalline configuration.

The polymer may contain a plurality of different plasticisers.

The polymer may conduct by anionic conduction. It has been found that it is possible to provide anionically conducting polymers which exhibit conductivity comparable to H+ conducting membranes. Alternatively, the polymer may conduct by cationic conduction, which may be proton conduction.

Advantageously, the polymer is formed from the polymerisation of a monomer which comprises a group of sub-formula (I) x~ ~
N R' R1z where R2 and R3 are independently selected from (CR7 R8)n, or a group CR9R'0, CR7R$CR9R10 or CR9R'0CR7 R$ where n is 0, 1 or 2, R7 and R$ are independently selected from hydrogen, halo or hydrocarbyl, and either one of R9 or R10 is hydrogen and the other is an electron withdrawing group, or R9 and R10 together form an electron withdrawing group, and R4 and R 5 are independently selected from CH or CR" where R" is an electron withdrawing group;

the dotted lines indicate the presence or absence of a bond, Xl is a group CX2 X3 where the dotted line bond to which it is attached is absent and a group where the dotted line bond to which it is attached is present, Y1.is a group where the dotted line bond to which it is attached is absent and a group CYZ

where the dotted line bond to which it is attached is present, and X2, X 3, Y
2 and Y 3 are independently selected from hydrogen, fluorine or other substituents;

R' is selected from hydrogen, halo, nitro or hydrocarbyl, optionally substituted or interposed with functional groups;

R12 is selected from hydrogen, halo, nitro, hydrocarbyl, optionally substituted or interposed with functional groups, or -R3-0 Y1; and Z is an anion of charge m.

Preferably, the poiymer is formed from the polymerisation of a dienyl quaternary amine, most preferably from polymerisation of a'starting material which comprises a group of sub-formula (II) 2" R'~

~~ \ x, ~
N -k-R' y where R2 and R3 are independently selected from (CR7 R$)n, or a group CR9R'o CR'R$CR9R10 or CR9R'0CR7 R$ where n is 0, 1 or 2, R7 and R8 are independently selected from hydrogen, halo or hydrocarbyl, and either one of R9 or R10 is hydrogen and the other is an electron withdrawing group, or R9 and R10 together form an electron withdrawing group, and R4 and R 5 are independently selected from CH or CR" where R" is an electron withdrawing group;

the dotted lines indicate the presence or absence of a bond, Xl is a group CX2 X3 where the dotted line bond to which it is attached is absent and a group CX2 where the dotted line bond to which it is attached is present, Y, is a group 5 CY2Y3 where the dotted line bond to which it is attached is absent and a group CYZ where the dotted line bond to which it is attached is present, and X2, X
3, Y 2 and Y 3 are independently selected from hydrogen and fluorine;

and R' is hydrogen or hydrocarbyl, and Z is an anion of charge m.

As used herein, the expression "in the substantial absence of solvent"
means that there is either no solvent present or there is insufficient solvent present to completely dissolve the reagents, although a small amount of a diluent may be present to allow the reagents to flow.

Conditions under which polymerisation occurs include the influence of radiation or an electron beam, heat or the presence of a chemical initiator.
Radiation or electron beam induced polymerisation is suitably effected in the substantial absence of a solvent.

Preferably, R7 and R 8 are independently selected from fluoro, chloro, alkyl or H. In the case of alkyl, methyl is most preferred.

It is possible that at least one, and possibly all, of X2, X3, Y2 and Y3 is a substituent other than hydrogen or fluorine. Preferably at least one, and possibly all, of X2, X3, Y2 and Y3 is an optionally substituted hydrocarbyl group.
In such. embodiments, it is preferred that at least one, and most preferably all, of X2, X3, YZ and Y3 is an optionally substituted alkyl group. Particularly preferred examples are C, and C4 alkyl groups, especially methyl or ethyl.
Alternatively, at least one, and preferably all, of X2, X3, Y2 and Y3 are aryl and/or heterocyclic, such as pyridyl, pyrimidinyl, or a pyridine or pyrimidine containing group.

In preferred embodiments, Xl and Y' are groups CX2 X3 and CYlY2 respectively and the dotted lines represent an absence of a bond. Thus preferred compounds are those of sub-formula (IA) x3 N-~~ CrA]
' ~s3 where R1, R2 , R3, R4, R5, R6, X2, X3, Y2 and Y3 are as defined above. One or more such starting materials may be polymerised together. When more than one starting material is used, a copolymer will result.

When the dotted bonds in sub formula (1) are present, the resulting polymer will comprise polyacetylene chains. This can lead to a conjugated system with the possibility of associated conductivity.

Suitably the starting material is one which will cyclopolymerise in the sort of conditions used in polymer production. This may comprise the application of radiation, such as UV radiation, where necessary in the presence of a photoinitiator, the application of heat (which may be in form of IR
radiation), where necessary in the presence of an initiator, by the application of other sorts of initiator such as chemical initiators, or by initiation using an electron beam.
The expression "chemical initiator" as used herein refers to compounds which can initiate polymerisation such as free radical initiators and ion initiators such as cationic or anionic initiators as are understood in the art.

Preferably, the starting materials polymerise under the influence of ultraviolet radiation or thermal radiation or both. Cyclopolymerisation may take place either spontaneously or in the presence of a suitable initiator.
Examples of suitable initiators include 2, 2' - azobisisobutyronitrile (AIBN), aromatic ketones such as benzophenones in particular acetophenone; chlorinated acetophenones such as di- or tri-chloracetophenone; dialkoxyacetophenones such as dimethoxyacetophenones (sold under the trade name "Irgacure 651") dialkylhydroxyacetophenones such as dimethylhydroxyacetophenone (sold under the trade name "Darocure 1173"); substituted dialkylhydroxyacetophenone alkyl ethers such as compounds of formula RP

where RY is alkyl and in particular 2, 2-dimethylethyl, Rx is hydroxyl or halogen such as chloro, and Rp and Rp are independently selected from alkyl or halogen such as chloro (examples of which are sold under the trade names "Darocure 1116" and "Trigonal P1"); 1-benzoylcyclohexanol-2 (sold under the trade name "Irgacure 184"); benzoin or derivatives such as benzoin acetate, benzoin alkyl ethers in particular benzoin butyl ether, dialkoxybenzoins such as dimethoxybenzoin or deoxybenzoin; dibenzyl ketone; acyloxime esters such as methyl or ethyl esters of acyloxime (sold under the trade name "Quantaqure PDO"); acylphosphine oxides, acylphosphonates such as dialkylacylphosphonate, ketosulphides for example of formula C --- CN
lt 0 Rz where RZ is alkyl and Ar is an aryl group; dibenzoyl disulphides such as 4, 4'-dialkylbenzoyldisuphide; diphenyidithiocarbonate; benzophenone; 4, 4'-bis (N, N-dialkyamino) benzophenone; fluorenone; thioxanthone; benzil; or a compound of formula tl where Ar is an aryl group such as phenyl and RZ is alkyl such as methyl (sold under the trade name "Speedcure BMDS").

As used herein, the term "alkyl" refers to straight or branched chain alkyl groups, suitably containing up to 20 and preferably up to 6 carbon atoms. The term "alkenyl" and "alkynyl" refer to unsaturated straight or branched chains which include for example from 2-20 carbon atoms, for example from 2 to 6 carbon atoms. Chains may include one or more double to triple bonds respectively. In addition, the term "aryl" refers to aromatic groups such as phenyl or naphthyl.

The term "hydrocarbyl" refers to any structure comprising carbon and hydrogen atoms. For example, these may be alkyl, alkenyl, alkynyl, aryl such as phenyl or napthyl, arylalkyl, cycloalkyl, cycloalkenyl or cycloalkynyl.
Suitably they will contain up to 20 and preferably up to 10 carbon atoms. The term "heterocylyl" includes aromatic or non-aromatic rings, for example containing from 4 to 20, suitably from 5 to 10 ring atoms, at least one of which is a heteroatom such as oxygen, sulphur or nitrogen. Examples of such groups include furyl, thienyl, pyrrolyl, pyrrolidinyl, imidazolyl, triazolyl, thiazolyl,, tetrazolyl, oxazolyl, isoxazolyl, pyrazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, quinolinyl, isoquinolinyl, quinoxalinyl, benzthiazolyl, benzoxazolyl, benzothienyl or benzofuryl.

The term "functional group" refers to reactive groups such as halo, cyano, nitro, oXO, C(O) nRa, ORa, S(O) tRa, NRbRc, OC (0) NRbR , C(O)NRbR , OC(O)NRbR , -NR7C(O)nR6, -NRaCONRbR , - C=NORa, -N=CRbR , S(O) tNRbR , C(S)nRa, C(S)ORa, C(S)NRbR or - NRbS (O)tRa where Ra, Rb and Rc are independently selected from hydrogen or optionally substituted hydrocarbyl, or Rb and Rc together form an optionally substituted ring which optionally contains further heteroatoms such as S(O)s, oxygen and nitrogen, n is an integer of 1 or 2, t is 0 or an integer of 1-3. In particular the functional groups are groups such as halo, cyano, nitro, oxo, C(O)nRa, ORa, S(O)tRa, NRbR , OC(O)NRbR , C(O)NR'R , OC(O) NRbRc, -NR7C(O)nR6, -NRaCONRbR , - NRaCSNRbRc, C=NORa, -N=CRbR , S(O)tNRbRc, or -NRbS(O)tRa where Ra, Rb and R , n and t are as defined above.

The term "heteroatom" as used herein refers to non-carbon atoms such as oxygen, nitrogen or sulphur atoms. Where the nitrogen atoms are present, they will generally be present as part of an amino residue so that they will be substituted for example by hydrogen or alkyl.

The term "amide" is generally understood to refer to a group of formula C(O)NRaRb where Ra and Rb are hydrogen or an optionally substituted hydrocarbyl group. Similarly, the term "sulphonamide" will refer to a group of formula S(O)2NRaRb.

The nature of any electron withdrawing group or groups additional to the 5 amine moiety used in any particular case will depend upon its position in relation to the double bond it is required to activate, as well as the nature of any other functional groups within the compound. The term "electron withdrawing, group"
includes within its scope atomic substituents such as halo, e.g. fluro, chloro and bromo.

10 Where R" is an electron withdrawing group, it is suitably acyl such as acetyl, nitrile or nitro.

Preferably Xl, X2, Y' and Y2 are all hydrogen.

Suitable groups Ra include hydrogen or methyl, in particular hydrogen.
A preferred group of polymers is of the following structure A
~' MoJ

where A is a bond or CH2, R2, R3, R4, R5 and R' are as defined in relation to sub-formula (I) or (II), and y is an integer in excess of 1, preferably in excess of 5. The invention includes within its scope oligomers, in which instances y is typically between 2 and 15, preferably between 5 and 12. Higher molecular weight polymers are also within the scope of the invention, in which instance y can be in excess of 100.

Zm- may be a halide ion, a boride ion, triflate, PFs , HS04 , H2P04 , BF4 , N03 , or a carboxylic acid ester, preferably a carboxylic acid ester having an alkyl or a per-fluorinated alkyl group of greater than five carbon atoms, most preferably octanoate or per-fluoro octanoate. Also possible are other anions having hydrocarbyl or substituted hydrocarbyl moieties. Anions having branched hydrocarbyl moieties may disrupt the formation of crystals and hence increase non-crystallinity.

In the group of sub-formula (I), Xl and Y' may represent CXIX3 and CY2Y3 respectively, the dotted bonds being absent and X2, X3, Y2 and Y3 being all hydrogen.

The starting material may be a compound of structure (III) zM)~ 2 ~
~
Rb N+R ~

where X', Y', R2, R3, R4, R5 and the dotted bonds are as defined in relation to formula (I) above, r is an integer of 1 or more, and R6 is a bridging group, an optionally substituted hydrocarbyl group, a perhaloalkyl group, a siloxane group or an amide, of valency r.

Where in the compound of formula (III), r is 1, compounds can be readily polymerised to form a variety of polymer types depending upon the nature of the group R6. Examples of groups which are commonly found in polymer technology are included below in Table 1.

Monomers of this type may be represented as structure (IV) (Z6t.--- N L'Vi -~ R

where X2, X3, YZ, Y3, R', RZ, R3, R4, and R5 are as defined in relation to formula (I) above, R6' is an optionally substituted hydrocarbyl group, a perhaloalkyl group, a siloxane group or an amide.

The invention may also be applied to other sorts of polymers; for example, where in the compounds of formula (III), r is greater than one, polymerisation can result in polymer networks. Particular examples are compounds of formula (III) as defined above, where R6 is a bridging group and r is an integer of 2 or more, for example from 2 to 8 and preferably from 2 - 4.
Embodiments in which r is two are particularly preferred.

On polymerisation of these such compounds, networks are formed whose properties maybe selected depending upon the precise nature of the R6 group, the amount of chain terminator present and the polymerisation conditions employed.

R' may be an alkyl group, preferably having less than three carbon atoms, most preferably methyl. Alternatively, R' may be H. Embodiments in which R' is H may be useful for providing proton conduction mechanisms.

In preferred structures, R6 or R6' comprises a straight or branched chain alkyl group, optionally substituted or interposed with functional groups.

R6 or R6' may be an optionally substituted hydrocarbyl group having four or more carbon atoms. Preferably, R6 or R6' is an alkyl group, most preferably a straight chain alkyl group, although R6 or R6' may be a branched chain alkyl group. R6 or R6' may have between five and twenty carbon atoms, preferably between eight and fourteen carbon atoms, most preferably ten carbon atoms.

In particularly preferred embodiments, the starting material is a compound of formula (V) cu--cNZ~ Z~'~~ ~ (~-n~ cNz __ c~4 \
c~cZ H 4 N CC1(z~ , o - (V -~ ~ Z. CK ~, ! ~ ,, ~ GH ~

CH -- CF4L Gl-k 2- C4-( The starting material may be a compound of formula (VI) Ct~z~--- CH
CN CCkz~ - N u ~1-{
3 ~~ [v r~
~ C HZ
Ci~Z+. ck~

In the embodiments of formulae (v) and (vi), Z'- may be PF6 , per-fluoro octanoate or triflate.

R6 or R6' may comprise a perhalo hydrocarbyl group, preferably a perfluoro hydrocarbyl group. R6 or R6' may comprise a perhaloalkyl group such as a perfluoroalkyl group, for example of from 1 to 3 carbon atoms such as a perhalomethyl group, in particular perfluoromethyl.

R6 or R6' may comprise a sulfonated group and/or an imidazole containing group.

Examples of suitable bridging groups include those found in polyethylenes, polypropylenes, nylons, as listed in Table 1. Further examples of bridging groups can be found in WO 00/06610.

Table 1 Polymer Type Repeat Unit of Bridging Group Polyethylene CH2 Polystyrene CH2CH(C6H5) where the phenyl ring is optionally substituted Polyisobutylene CH2CH(CH(CH3)2) Polyisoprene CH2CH(CH3) Polytetrafluoroethylene CH2(CF2)XCH2 Polyvinylidenefluoride CH2(CF2CH2)X
Polyethyleneoxide (OCH2CH(CH3))xO

Nylon CH2(NHCOCH2)xCH2 Peptide CH2 (NHCOCHR)xCH2 Polyurethanes -NH-CO-O-Polyesters -RC(O)OR'-where R and R' are organic groups such as hydrocarbyl Polysiloxanes e.g. -Si02-, -R2SiO- or -R2Si2O3- where R is an organic group such as hydrocarbyl Polyacrylates -CH2C(COOH)H-Polyureas -NHCONH-Polythioureas -NH-C(S)-NH-The invention includes the possibility of producing copolymers where another monomeric compound, for example one which is not of formula (I), is mixed with the compound of formula (I) prior to polymerisation. Such monomers are known in the art. Additionally or alternatively the solid ionically conductive 5 polymer may be provided in a composite structure with one or more other materials in order to produce desired mechanical and/or electrochemical properties. The solid ionically conductive polymer may be utilised in combination with one or more inorganic materials such as Si02, tungsten compounds, and glass fibre.

10 In embodiments in which R12 is not -R3-R5 __ _: Yl, the monomer is preferably of the following formula (2fn_1 (?2 ---- R ~' .~.. , 6 N+Rr(2'Z x where R6 is as previously defined and may be a group R6'as previously 15 defined.

The solid ionically conductive polymer may be self-supporting, such as in the form of a membrane, or may be used in conjunction with a substrate. Thus, according to a second aspect of the invention there is provided a substrate and a solid ionically conductive polymer according to the first aspect of the invention located therein or thereon.

The substrate may be a solid substrate, or a structure having voids therein, such as a mesh, a web or a porous substrate. A mesh or web structure can be used to reinforce the polymer. Nylon mesh or web structures may be employed.

In embodiments in which the structure is porous, the solid ionically conductive polymer may be located in the pores of the substrate. The plasticiser may be less prone to washing out of the polymer in such structures. The structure can be produced by soaking an appropriate monomer into the pores of the substrate and polymerising in situ. The plasticiser may be present with the monomer when the polymerisation takes place.

Preferably, the substrate is a ceramic or a zeolite. In this way conductive materials can be provided which are tough, can operate at high temperatures and do not require the presence of water to conduct.

The structure may be in the form of an ionically conductive membrane.
Such conductive membranes have numerous applications, such as in fuel cells.
According to a third aspect of the invention there is provided a method of producing a solid ionically conductive polymer having repeat units of a quaternary amine including the steps of polymerising a quaternary amine starting material and providing a plasticiser in the polymer present in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.
Advantageously, the quaternary amine starting material may be sprayed onto a target structure prior to the step of polymerising. This is an extremely effective and practical way of applying a conductive coating.

The step of polymerising may be effected by the application of radiation, where necessary in the presence of an initiator. Preferably, the polymerisation is effected by the application of ultraviolet radiation.

Alternatively, the step of polymerising may be effected by the application of heat, where necessary in the presence of an initiator.

In one embodiment the plasticiser is mixed with the starting material prior to the step of polymerising.

Alternatively, the plasticiser may be added to the polymer after or during the step of polymerising.

International Publications WO 00/06610, WO 00/06533, WO 00/06658, WO 01/40814 and WO 01/74919 disclose the preparation of monomers and polymers of the dienyl type. International Publication WO 01/74919 also discloses the preparation of monomers and polymers formed from quaternary ammonium'species having a single vinyl type group.

According to a fourth aspect of the invention there is provided a method of producing a structure including the steps of providing a porous substrate, introducing a quaternary amine starting material and a plasticiser into the pores of the substrate, and polymerising the starting material to produce a solid ionically conductive polymer, the plasticiser being present in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.
According to a fifth aspect of the invention there is provided a fuel cell including a solid ionically conductive polymer according to the first aspect of the invention. The fuel cell may include an ionically conductive membrane as described in respect of the second aspect of the invention, preferably a proton conductive membrane.

Whilst the invention has been described above, it extends to any inventive combination or sub-combination of the features set out above or in the following description or claims.

Example I

The target molecule 1 is shown below.

CH -- CI4 2 (~ C+I 2 C~-E

CNz H N N~H \ c~~ 2 c H Z ~ ~ Ct~z A mixture of 1,10 - dibromodecane (23.8g), diallylamine (15.4g) and K2CO3 (58.0g) in absolute ethanol were refluxed overnight with a drying arm over the condenser. Reaction progress was checked using TLC. Solid KBr and excess K2CO3 were removed from the solvent by filtration. Ethanol was removed by rotary evaporation together with any remaining diallylamine. Any sold KBr appearing at this point in the synthesis can be dissolved in dichloromethane (DCM) and filtered. Monomers obtained using dry silica gel flushed through with dry DCM. To a solution of monomer in methanol or dry DCM, a 6M aqueous solution of hydroperfluoric acid (HPF6) is added until the mixture reaches a pH

of about 5-6. The water is allowed to evaporate, leaving a quaternary amine.
Example 2 To the quaternary amine 1 prepared in Example 1, propylene carbonate and 3wt% of Irgacure 184 photoinitiator was added, dissolved by gentle heating (at ca. C) and mixing using a whilimixer. Various amounts of propylene carbonate were added in different experiments, but mixtures having between 25 and 60% by weight of propylene carbonate were found to provide the best results.

The mixture was cured by exposure to UV radiation. Exposure times depend on the UV radiation source and exposure conditions: in this instance exposure involved two passes each of -1 sec to a 600W/cm Ga doped mercury UV source. The polymer thus formed was found to be conductive.

Example 3 The mixture of quaternary amine 1, photoiniator and propylene carbonate prepared in Example 2 was added to a zeolite and polymerised in situ by exposure to UV radiation. The zeolite exhibited conductivity.

Example 4 An analogue of the target molecule 1 was prepared in which the anion is per-fluoro octanoate. The analogue was prepared using the method described in Example 1, except that aqueous perfluorooctanoic acid was used instead of hydroperfluoric acid. The analogue was polymerised using the methodology of Example 2, and the resulting polymer exhibited a marginally higher conductivity than the polymer of Example 2.

Example 5 An analogue of the target molecule 1 was prepared in which the anion is triflate. The analogue was prepared using the method described in Example 1, except that triflic acid (CF3SO3H) was used instead of hydroperfluoric acid.
The analogue was polymerised using the methodology of Example 2, and the resulting polymer exhibited a marginally higher conductivity than the polymer of Example 2.

The reaction scheme of bromoalkane, diallylamine and K2CO3 is a general one that can be used to prepare monomers for subsequent polymerisation and use according to the invention. Bisubstituted bromoalkanes (particularly where the bromo substitution is at either end of the alkyl chain) are used to produce monomers having two dienyl end groups. Singly substituted bromo alkanes are used to produce monomers having one dienyl end group.

Claims

1. A solid ionically conductive polymer having repeat units of a quaternary ammonium and including a plasticiser in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.

2. A solid ionically conductive polymer according to claim 1 in which the plasticiser is present as an additive to the polymer.

3. A solid ionically conductive polymer according to claim 2 in which the plasticiser is propylene carbonate.

4. A solid ionically conductive polymer according to claim 1 in which the polymer is self-plasticising.

5. A solid ionically conductive polymer according to claim 4 in which the polymer includes an anion present as a counterion to the quaternary ammonium, and the anion itself acts as a plasticiser.

6. A solid ionically conductive polymer according to claim 4 in which the quaternary ammonium itself acts as a self-plasticiser.

7. A solid ionically conductive polymer according to any previous claim which conducts by anionic conduction.

8. A solid ionically conductive polymer according to any one of claims 1 to 6 which conducts by cationic conduction.

9. A solid ionically conductive polymer according to claim 8 which conducts by proton conduction.

10. A solid ionically conductive polymer according to any previous claim in which the polymer is formed from the polymerisation of a dienyl quaternary ammonium.

11. A solid ionically conductive polymer according to claim 10 in which the polymer is formed from polymerisation of a starting material which comprises a group of sub-formula (I) where R2 and R3 are independently selected from (CR7R8)n, or a group CR9R10, CR7R8CR9R10 or CR9R10CR7R8 where n is 0, 1 or 2, R7 and R8 are independently selected from hydrogen, halo or hydrocarbyl, and either one of R9 or R10 is hydrogen and the other is an electron withdrawing group, or R9 and R10 together form an electron withdrawing group, and R4 and R5 are independently selected from CH or CR11 where R11 is an electron withdrawing group;

the dotted lines indicate the presence or absence of a bond, X1 is a group CX2 X3 where the dotted line bond to which it is attached is absent and a group where the dotted line bond to which it is attached is present, Y1 is a group where the dotted line bond to which it is attached is absent and a group CY2 where the dotted line bond to which it is attached is present, and X2, X3, Y2 and Y3 are independently selected from hydrogen, fluorine or other substituents;

R1 is selected from hydrogen, halo, nitro or hydrocarbyl, optionally substituted or interposed with functional groups;

R12 is selected from hydrogen, halo, nitro, hydrocarbyl, optionally substituted or interposed with functional groups, or -R3-R5=Y1; and Z is an anion of charge m.

12. A solid ionically conductive polymer according to claim 11 in which the polymer is formed from polymerisation of a starting material which comprises a group of sub formula (II) where R2 and R3 are independently selected from (CR7R8)n, or a group CR9R10, CR7R8CR9R10 or CR9R10CR7R8 where n is 0, 1 or 2, R7 and R8 are independently selected from hydrogen, fluoro, or hydrocarbyl, and either one of R9 or R10 is hydrogen and the other is an electron withdrawing group, or R9 and R10 together form an electron withdrawing group, and R4 and R5 are independently selected from CH or CR11 where R11 is an electron withdrawing group;

the dotted lines indicate the presence or absence of a bond, X1 is a group CX2X3 where the dotted line bond to which it is attached is absent and a group CX2 where the dotted line bond to which it is attached is present, Y, is a group CY2Y3 where the dotted line bond to which it is attached is absent and a group CY2 where the dotted line bond to which it is attached is present, and X2, X3, and Y3 are independently selected from hydrogen and fluorine;

and R1 is hydrogen or hydrocarbyl, and Z is an anion of charge m.

13. A solid ionically conductive polymer according to claim 11 or claim 12 in which the polymer is formed by a cyclopolymerisation of the starting material.

14. A solid ionically conductive polymer according to any one of claims 11 to 13 wherein Z m- is a halide ion, a boride ion, triflate, PF6-, HSO4-, H2PO4-, BF4-, NO3-, or a carboxylic acid ester, preferably a carboxylic acid ester having an alkyl or a per-fluorinated alkyl group of greater than five carbon atoms, most preferably octanoate or per-fluoro octanoate.

15. A solid ionically conductive polymer according to any one of claims 11 to 14 where, in the group of sub-formula (I) or (II), X1 and Y1 represent CX2X3 and CY2Y3 respectively, the dotted bonds are absent and X2, X3, Y2 and Y3 are all hydrogen.

16. A solid ionically conductive polymer according to any one of claims 11 to 15 wherein the starting material is a compound of structure (III) where X1, Y1, R2, R3, R4, R5 and the dotted bonds are as defined in claim 11, r is an integer of 1 or more, and R6 is a bridging group, an optionally substituted hydrocarbyl group, a perhaloalkyl group, a siloxane group or an amide, of valency r.

17. A solid ionically conductive polymer according to claim 16 wherein the starting material comprises a compound of formula (IV) where X2, X3, Y2, Y3, R2, R3, R4, and R5 are as defined in claim 11, R6' is an optionally substituted hydrocarbyl group, a perhaloalkyl group, a siloxane group or an amide.

18. A solid ionically conductive polymer according to claim 16 or claim 17 in which r is two.

19. A solid ionically conductive polymer according to any one of claims 16 to 18 wherein R6 or R6' comprises a straight or branched chain alkyl group, optionally substituted or interposed with functional groups.

20. A solid ionically conductive polymer according to any one of claims 16 to 19 wherein R6 or R6' is an optionally substituted hydrocarbyl group having four or more carbon atoms.

21. A solid ionically conductive polymer according to claim 20 in which R6 or R6' is an alkyl group, preferably a straight chain alkyl group.

22. A solid ionically conductive polymer according to claim 21 in which R6 or R6' has between five and twenty carbon atoms, preferably between eight and fourteen carbon atoms, most preferably ten carbon atoms.

23. A solid ionically conductive polymer according to claim 22 in which the starting material is a compound of formula (V)

24. A solid ionically conductive polymer according to any one of claims 11 to 22 in which R1 is an alkyl group, preferably having less than three carbon atoms, most preferably methyl.

25. A structure including a substrate and a solid ionically conductive polymer according to any previous claim located therein or thereon.

26. A structure according to claim 25 in which the substrate is porous, and solid ionically conductive polymer is located in the pores of the substrate.

27. A structure according to claim 26 in which the substrate is a ceramic.

28. A structure according to claim 26 in which the substrate is a zeolite.

29. A structure according to any one of claims 25 to 28 in the form of an ionically conductive membrane.

30. A method of producing a solid ionically conductive polymer having repeat units of a quaternary ammonium including the steps of polymerising a quaternary ammonium starting material and providing a plasticiser in the polymer present in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.

31. A method according to claim 30 in which the quaternary ammonium starting material is sprayed onto a target structure prior to the step of polymerising.

32. A method according to claim 30 or claim 31 in which the step of polymerising is effected by the application of radiation, where necessary in the presence of an initiator.

33. A method according to claim 32 in which the polymerisation is effected by the application of ultraviolet radiation.

34. A method according to claim 30 or claim 31 in which the step of polymerising is effected by the application of heat, where necessary in the presence of an initiator.

35. A method according to any one of claims 30 to 34 in which the plasticiser is mixed with the starting material prior to the step of polymerising.

36. A method according to any one of claims 30 to 34 in which the plasticiser is added to the polymer after or during the step of polymerising.

37. A method of producing a structure including the steps of providing a porous substrate, introducing a quaternary ammonium starting material and a plasticiser into the pores of the substrate, and polymerising the starting material to produce a solid ionically conductive polymer, the plasticiser being present in an amount sufficient to render the polymer non-crystalline thereby increasing conductivity.

38. A fuel cell including a solid ionically conductive polymer according to any one of claims 1 to 24.

39. A fuel cell including an ionically conductive membrane according to claim 29.

40. A polymer, structure, fuel cell or method substantially as described herein.