WO 99/32537 discloses polymeric material derivable from a triarylamine derivative as monomer and the use of such polymers as a CTM in opto-electronic devices.

GB 9914167. 3 discloses a composition comprising a CTM polymeric material derivable from a triarylamine derivative as monomer and an additive which improves the CTM properties of the polymer, especially its resistance to ozone associated with light and/or corona-induced deterioration of the CTM polymer. The corona-induced deterioration is often referred to as"parking deletion"of the latent image or"white drop- out"in the CTL.

However, the incorporation of additives in a CTL containing the CTM further complicates manufacture of opto-electronic devices and can affect plasticisation of the CTL leading to reduced efficiency. More importantly the additive can migrate to the surface of the CTL and/or into the Charge Generating Layer (hereinafter CGL) and can result in loss of sensitivity, increase in dark decay and/or image deletion. It has now been found that this"parking deletion"effect can be significantly reduced if the anti-oxidant and/or radical scavenger is covalently bound to the triarylamine moiety either directly or indirectly.

According to the invention there is provided a Charge Transport Material (CTM) having one or more arylene groups which contains one or more residues of an anti- oxidant or radical scavenger which is covalently bound either directly or indirectly to an arylene moiety of the CTM, including mixtures thereof. This is referred to hereinafter as the"Polymeric Material".

Preferably the CTM contains one or more diphenylamine or more preferably triphenylamine residues.

It is also preferred that the antioxidant is an aryl residue having a hydroxy, thiol or amine group and one or more aryl, alkyl or alkoxy groups adjacent to the hydroxy, thiol or amino group. Preferably, the antioxidant contains two groups adjacent to the hydroxy, thiol or amine group. Preferred adjacent groups are C, 6-alkyl and C, 6-alkoxy which may be linear or branched. Preferably, the aryl residue is naphthyl or more preferably phenyl.

It is also preferred that the antioxidant is a naphthol or more preferably a phenol and especially a phenol containing one or more tert-butyl groups adjacent to the phenolic hydroxyl group.

The antioxidant may also be an optionally N-substituted piperidine especially one carrying geminal C, 6-alkyl groups such as methyl adjacent to the ring nitrogen atom.

Examples of hindered phenols and hindered amines which may be used to provide a residue of an antioxidant or radical scavenger in the Polymeric Material according to the invention are these disclosed in US 5, 948, 579.

When the antioxidant is a hindered phenol, hindered phenyl mercaptan or piperidine derivative, it is preferably linked to the arylene moiety of the CTM via the 4- position of the phenol, phenyl mercaptan or piperidine.

Naphthyl and phenyl groups containing hydroxy, thiol or amine groups together with one or more adjacent substituents are often referred to as"hindered"compounds, eg hindered phenols.

According to a further aspect of the invention there is a provided compound of formula 1 including mixtures thereof wherein Ar'and Ar2 are each, independently, arylene optionally substituted by one or more C, 40-hydrocarbyl groups which may themselves be substituted ; Ar3 is aryl optionally substituted by mercapto, hydroxy, alkoxy, amino, alkylamino or by one or more C140 hydrocarbyl groups which may themselves be substituted or substituted by a direct bond or bridging group linking different chain residues of formula 1 ; Y is N, S, Se, As or P ; n is zero or 1 and is zero when Y is S or Se ; m is from 1 to 2, 000 ; X'and X2 are each, independently, a bridging group or a direct bond ; A and B are each, independently, hydrogen, hydroxy, amino, substituted amino or a polymerisation terminating group ; and where at least one of A, B and Ar3 in each polymer chain is or contains the residue of an antioxidant and/or radical scavenger.

When m is greater than one, it is preferred that each atom represented by Y is the same.

Preferably, Y is N.

Ar', Ar'and Ar'may be the same or different arylene/aryl residues but are preferably the same. It is particularly preferred that each of Ar'and Ar2 is, independently, naphthylene, and especially phenylene. Preferably, substituents X'and Y and also X2 and Y occupy positions 1, 4 when Ar'and Ar2, respectively, represent naphthylene and phenylen. it is also preferred that Ar3 is naphthyl and especially phenyl.

When m is 2 or more and n is 1, the compound of formula 1 is polymeric and contains two or more substituents Ar3 In such a case, it is not necessary that every substituent Ar3 in any polymer chain is or contains the residue of an antioxidant or radical scavenger.

When Ar3 contains a direct bond linking different chain residues of formula 1, the group linking substituents Y in different chains is preferably phenylene-naphthylene, dinaphthylene and especially diphenylene.

When Ar3 contains a substituent which is a bridging group linking different chain residues of formula 1, the bridging group is preferably C, 6-alkylene which may be linear or branched such as- (CH2) 3- and-C (CH3) 2-.

When Ar3 contains a direct bond or a bridging group linking different chain residues of formula 1 and n is 1 and m is 2 or more it is possible to obtain a polymer matrix wherein chain residues of formula 1 contain more than one cross-linking group which is a direct bond or bridging group as disclosed hereinbefore. When such cross- linking groups are present it is preferred that no more than two chain residues of formula 1 are so linked and that the polymer matrix contains no more than 1 such direct bond or bridging group. It is much preferred that Ar3 is free from substituents which form a direct bond or bridging group linking different chain residues of formula 1.

When Ar'contains substituents, the substituents are preferably hydroxy, phenyl, hydroxyphenyl, trifluoromethyl, C1 6-alkyl which may be linear or branched or C, 6-alkoxy which may be linear or branched. Examples of Ar3 substituted by C, 6-alkyl are 4-methylphenyl, 3-methylphenyl, 2-methylphenyl and 2, 5-dimethylphenyl, 4-tert-butyl phenyl, 2, 4-dimethyl phenyl. Examples of Ar3 substituted by C, _6-alkoxy are 4-methoxyphenyl, 2-methoxy phenyl, 3-methoxy phenyl, 4-ethoxyphenyl and 2, 4-dimethoxyphenyl. Other examples of Ar3 are 4-hydroxyphenyl, biphenyl, 4- (N, N-diethylamino) phenyl and 3-trifluoromethyl phenyl.

As noted hereinbefore, Ar3 can be the residue of an antioxidant, such as a hindered phenol. By hindered phenol, it is meant a phenol residue which contains 1 or 2 phenyl or preferably C1 6-alkyl or Cl-, alkoxy groups which may be linear or branched which are adjacent to the phenolic hydroxy group. Examples of such groups Ar3 are 4- hydroxy-3-methyl phenyl, 4-hydroxy-3-methoxyphenyl, 3', 5'-di-tert-butyl-4'-hydroxy diphenyl methane and especially 3, 5-di-tert-butyl-4-hydroxy phenyl and 3, 5-di-tert butyl- 4-hydroxybiphenyl.

When Ar'and Ar2 are substituted, the substituents are preferably the same.

Preferred substituents are C, 6-alkyl and C, 6 alkoxy for example 2-methyl and 2- methoxy. It is however preferred that Ar'and Ar2 are not substituted.

Preferably, both X'and X2 represent a direct bond.

When A and B is substituted amino, it is preferably amino substituted by one or more C1 20-alkyl, preferably C, 6-alkyl groups such as diethylamine.

When A and B is a polymerisation terminating group, it can be any group which does not participate in chain propagation during the preparation of polymers of formula 1 wherein m is 2 or more. Preferably the polymerisation terminating group is C1 40- hydrocarbyl optionally substituted by amino, substituted amino, trifluoromethyl, hydroxy, cyano, nitro, or C, _6-alkyl, C, _6-alkoxy and alkylen such as CI-6-alkylene. Preferred hydrocarbyl groups are optionally substituted aromatic groups such as naphthyl and phenyl. Examples of polymerisation terminating groups are triphenylamino, 3- methylphenyl, 3-trifluoromethylphenyl, 4-methyl phenyl, 3-methoxy phenyl, 214- dimethylphenyl, 4-tert-butylphenol and phenyl.

As noted hereinbefore, A and/or B can also represent the residue of an antioxidant such as a hindered phenol or hindered amine. Examples of hindered phenols are phenols which contain one or more C, _6-alkyl or C, 6 alkoxy groups which may be linear or branched, such as those hindered phenol residues described hereinbefore for Ar3.

When A or B is alkylen, the alkylen chain links two chain residues of formula 1.

Preferred alkylen groups are 1, 3-propylene since this group extends the conjugation between adjacent linked chain residues of formula 1. However, it is much preferred that the substituent in A and/or B is other than alkylen.

It is particularly preferred that the compound of formula 1 is free from halogen substituents since these can adversely affect the efficiency of the polymers as CTM.

Preferably m is not less than 2, more preferably not less than 3 and especially not less than 4. It is also preferred that m is not greater than 1, 000, more preferably not greater than 500 and especially not greater than 200.

When the compound of formula 1 is polymeric, the method used to prepare such compounds often results in a mixture of polymers having different numbers of repeat units m. Preferably the average number of repeat units in such mixture of polymers is from 2 to 50 and especially from 4 to 20 since such mixtures have been found especially useful as CTM's. Particularly useful CTM's are those polymer mixtures where the average number of repeat units is from 6 to 14.

Mixtures of polymers of formula 1 are also preferred which exhibit a polydispersity (Mw/Mn) of from 1. 1 to 5 and especially from 1. 1 to 3 wherein Mw denotes weight average molecular weight and Mn denotes number average molecular weight.

According to a preferred aspect of the invention there is provided a mixture of polymers derived from a triarylamine derivative obtainable by reacting one or more monomers of formula 2 wherein Ar'and Ar'are each, independently, phenylen or naphthylene, optionally substituted by C, 40-hydrocarbyl which may itself be substituted : Ar6 is optional substituted phenyl or naphthyl, and Hal is halogen in an inert atmosphere and in an anhydrous aprotic solvent and in the presence of a zero- valent nickel triaryl-or trialkyl-phosphine complex and optionally in the presence of one or more polymerisation terminating compounds T-Hal wherein T is the residue of a polymerisation terminating group and Hal is halogen provided that at least one of T or Ar6 in each of the polymer chains is or carries the residue of an optionally protected antioxidant or radical scavenger.

The zero-valent nickel complex is preferably prepared by reducing either nickel chloride or bromide in the presence of magnesium, manganese and especially zinc and is preferably obtained using triphenylphosphine.

The reaction is also preferably carried out in the presence of 2, 2'-bipyridine, especially where the substituents in Ar, Ar, Ar', or T are electron donating groups or atoms.

The inert atmosphere may be provided by any of the inert gases of the Periodic Table according to Mendeleef but is preferably nitrogen.

The aprotic solvent may be any solvent which is inert to the reactants under the reaction conditions. Thus, it may be aliphatic or aromatic, carbocyclic or heterocyclic.

Examples of suitable solvents are aliphatic acid amides such as N, N-dimethyl formamide and N, N-dimethylacetamide, aromatic hydrocarbons such as toluene and xylene and heterocyclic solvents such as N-methyl pyrrolidine. N, N-dimethylacetamide is preferred.

The polymerisation reaction is very facile and is preferably carried out at a temperature from 50 to 150° C and especially from 70 to 90°C.

Coupling of aryl chlorides using a zero-valent nickel triphenylphosphine complex is disclosed in J. Org Chem Vol 51, No 14, 1986, 2627-2637.

Since the presence of acidic substituents such as phenolic hydroxy groups in T and/or Ar6 can result in the formation of arene and not an aryl-aryl bond, it is preferred to use a protected antioxidant or radical scavenger when making a mixture of polymers from the monomer of formula 2.

When Ar4 and Ars are substituted, the substituent is preferably C, 6-alkyl or C, 6- alkoxy which may be linear or branched.

When Ar6 is substituted, the substituent is preferably C1 6-alkyi, C, 6-alkoxy, cyano, halogen, amino, mercapto, trifluoromethyl or hydroxy. As noted hereinbefore, the group Ars may also be or contain the residue of an optionally protected hindered phenol or radical scavenger.

Preferred polymerisation terminating groups are preferably aryl such as naphthyl and especially phenyl which is optionally substituted. Preferred substituents are C, 6-alkyl, C, 6-alkoxy, optionally substituted amino such as phenyl-and diphenyl-amino, trifluoromethyl, halogen, cyano, mercapto, and hydroxy. As disclosed hereinbefore, it is much preferred that the polymerisation terminating group is or contains the residue of an optionally protected hindered phenol or hindered amine.

When the polymerisation terminating group is substituted by halogen as in dichlorobenzene the resultant polymer may contain two residues of the monomer of formula 2 which are linked by a phenylene-phenylene direct bond.

Halogen is preferably bromo, iodo and especially chloro.

When Ar6 is substituted by chloro, the polymer chain may be linked by two Ar6-Ar6 groups in different polymer chains.

When T and Ar6 is or carries the residue of an optionally protected antioxidant such as phenol, naphthol, phenyl-or naphthyl-mercaptan or hindered amine the protecting group is preferably acyl, alkoxycarbonyl, trialkylsilyl, triphenylsilyl or trialkylureido. Preferred acyl groups are acetyl and especially tert-butoxycarbonyl. In a preferred aspect when T and/or Ar6 is or carries the residue of a hindered phenol, the phenolic hydroxy group may be protected and deprotected using the conditions disclosed in Tetrahedron Letters 39 (1998) 2705-6. Thus, for example, the hindered phenol may be reacted with di-tert-butyldicarbonate in a suitable solvent such as acetonitrile, methylene chloride or hexane and optionally in the presence of N, N-dimethylaminopyridine. After polymerising the monomer of formula 2 or reacting it with a polymerisation terminating group T-Hal, the protecting group may be removed by hydrolysis using a mineral acid such as hydrochloric acid or an organic acid such as trifluoroacetic acid to regenerate the hindered phenol or naphthol moiety. This protection/deprotection is preferred when T-Hal is or carries the residue of hindered phenol or naphthol but is less necessary when Ar6 is or carries the residue of a hindered phenol or naphthol. Hence, a preferred mixture of polymers is derived from a monomer of formula 2 wherein Ar6 is or carries the residue of a hindered naphthol or phenol and wherein the group T is other than a polymerisation terminating group which is or carries the residue of a hindered naphthol or phenol.

Examples of monomers of formula 2 are : bis (N-4-chlorophenyl)-3-methylphenylamine ; bis (N-4-chlorophenyl)-4-methylphenylamine ;

bis (N-4-chlorophenyl)-2, 4-dimethylphenylamine ; bis (N-4-chlorophenyl)-4-(N, N-diethylamine) phenylamine ; bis (N-4-chlorophenyl)-3-trifluoromethyl) phenylamine ; bis (N-4-chlorophenyl) phenylamine ; bis (N-4-chlorophenyl)-2, 5-dimethylphenylamine ; bis (N-4-chlorophenyl)-3-methoxyphenylamine ; bis (N-4-chlorophenyl)-4-ethoxyphenylamine ; bis (N-2-methyl-4-chlorophenyl)-2, 4-dimethylphenylamine ; bis (N-4-chlorophenyl)-4- isopropyl phenylamine ; tris (N-4-chlorophenyl) amine ; bis (N-4-chlorophenyl)-3, 5-di-tert-butyl-4-hydroxyphenylamine ; 2, 2- (4-bis (4-chlorophenyl) amino-3', 5'-di-tert-butyl-4'-hydroxy) diphenylpropane ; bis (N-4-chlorophenyl)-3', 5'-di-tert-butyl-4'-hydroxybisphenylamine ; bis (N-4-chlorophenyl)-3, 5-di-tert-butyl-4-acetoxyphenylamine ; and bis (N-4-chlorophenyl)-3, 5-di-tert-butyl-4-tert-butoxycarbonylphenylamine Examples of polymerisation terminating groups are : 3-methyl chlorobenzene ; 4-methyl chlorobenzene ; 3-methoxy chlorobenzene ; 2, 4-methyl bromobenzene ; 4-chloro triphenylamine ; 4-tert-butyl bromobenzene ; chlorobenzene ; 1, 4-dichlorobenzene ; 1, 3-dibromobenzene ; 3, 5-di-tert-butyl-4-hydroxy chlorobenzene ; 3, 5-di-tert-butyl-4-hydroxy bromobenzene ; 3, 5-di methyl-4-hydroxy chlorobenzene 2, 2- (4-chloro-3', 5'-d i-tert-butyl-4'-hyd roxy)-d i phenyl propane ; 3, 5-di-tert-butyl-4-acetoxy-bromobenzene ; and 3, 5-di-tert-butyl-4-tert butoxycarbonyl-chlorobenzene The monomers of formula 2 may be made by any method known to the art and especially those methods disclosed in WO 99/32537. Thus, for example, an optionally substituted iodo benzene is reacted with an optionally substituted amino benzene in an inert atmosphere under anhydrous conditions in the presence of copper powder and a crown-ether such 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane ("18-crown-6"), potassium carbonate and an inert solvent. Typical solvents are halobenzenes such as dichlorobenzene. The reaction is preferably carried out at 150-250°C and especially 180 to 200°C.

Certain of the monomers of formula 2 are novel especially wherein Ar6 is or contains the residue of an optionally protected antioxidant or radical scavenger such as an optionally protected hindered phenol, hindered mercaptan or hindered amine.

Thus, according to a further aspect of the invention there is provided a compound of formula 2 wherein Ar, Ar* and Ha ! are as defined hereinbefore and Ars is or contains the residue of an optionally protected anti-oxidant or radical scavenger.

When the monomer of formula 2 is polymerised in the absence of a polymerisation terminating compound T-Hal, the resulting polymer chains are longer than when polymerisation is carried out in the presence of T-Hal. Preferably T-Hal is present in order to control the chain length or degree of polymerisation. T-Hal may be introduced at any stage of the polymerisation of the monomer of formula 2. Thus, for example, T-Hal may be present at the start of polymerisation if relatively short polymer chains are required or T-Hal may be introduced at a later stage of polymerisation if longer polymer chains are required. In some instances it is preferred to add a mixture of T-Hal and monomer of formula 2 to the zero-valent nickel triaryl-or trialkyl-phosphine complex. It will be clear to the skilled person that by adding T-Hal and/or monomer of formula 2 to the zero-valent nickel complex at any stage during the polymerisation enables the degree of polymerisation of the resultant polymer mixture to be controlled.

When X'or X2 in formula 1 is other than a direct bond, the end-group or groups may be conveniently prepared by reacting one of the groups Hal in the monomer of formula 2 with a compound A-X'-H or B-X2-H wherein A, B, X'and x2 are as defined hereinbefore.

Whereas the above process is designed to produce mixtures of polymers it will be appreciated that it is also possible to make compounds containing the residue of only one repeat unit of formula 2. Hence, as a further aspect of the invention there is provided a compound of formula 3. wherein Ar4, Ars and Ars are as disclosed hereinbefore and T'and T2 are either H, Hal or a polymerisation terminating group provided that at least one of T'and T2 is a polymerisation terminating group. When T'and/or T2 is a polymerisation terminating group it is as defined for T.

As noted hereinbefore, the Polymeric Material may be used as a Charge Transport Material (CTM) in electroreprography. The Polymeric Material may be used as the sole CTM or it may be combined with other CTM's. Thus, it may be combined with any of the polymeric CTM's which contain one or more di-or tri-phenylamine residues.

Examples of such other CTM's are those described in US 5, 948, 579. Other examples of

CTM's are triarylamines, hydrazones, carbazoles, triphenylmethanes, oxazoles, oxadiazoles, styrylics, stilbenes, butadienes and mixtures thereof. It is preferred, however, that the other CTM is chemically anologous to the Polymeric Material but is free from a covalently bound residue of an anti-oxidant or radical scavenger. A much preferred other CTM is a polymeric material as disclosed in WO 99/32537.

Thus, according to a further aspect of the invention there is provided a composition comprising the Polymeric Material and one or more other CTM which does not contain a residue of an antioxidant or radical scavenger which is covalently bound either directly or indirectly to an arylene moiety of the CTM.

The amount of Polymeric Material to said other CTM can vary from 99 : 1 to 1 : 99.

The Polymeric Material typically constitutes one component of an electro- reprographic laminate which comprises an electro-conductive support, a CGL containing one or more CGM and a CTL containing one or more CTM. In a less preferred variant the CTL and CGM can be combined into a single layer containing both the CGM and CTM.

The CGL preferably lies between the CTL and the support.

Examples of the electro-conductive support are metals such as aluminium, nickel, chromium and stainless steel ; plastic film material coated with aluminium, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, vanadium oxide or paper or plastic film coated or impregnated with an electro-conductivity imparting agent. The support may be any appropriate shape such as plate, drum or belt.

The CGM may be an inorganic photo-conductive material such as amorphous selenium, a crystalline selenium alloy, a selenium-arsenic alloy, other selenium compound or selenium based alloy, granular selenium, zinc oxide and titanium oxide. Alternatively, the CGM may be an organic dye or pigment such as phthalocyanine, squalene, anthanthrone, perylene, azo, anthraquinone, pyrene, pyrilium salt or thiapyrilium salt.

Other CGM's are disclosed in WO 99/32537.

It is particularly preferred that the CGM is a phthalocyinine which may be metal- free or in the form of a complex with a metal or metal oxide such as titanium, gallium and/or vanadium. The phthalacyanine CGM may be in any polymorphic form. It is especially preferred that the CGM is titanyloxyphthalocyanine-(TiOPc) in a polymorphic form known as I (j3),) II (--a) lil (-Y or y), X or Z. Polymorphic forms I and IV are especially preferred.

The CGL may be formed by vacuum deposition of a CGM or by preferably applying a liquid coating comprising a CGM dispersed in a binder resin optionally in the presence of an organic liquid. Examples of suitable binder resins are polyvinyl butyral resins, polyvinyl formal resins, polyvinyl acetal resins, such as partially acetalized polyvinyl acetal resins, acetoacetal, polyamide resins, polyester resins, modified other- type polyester resins, polycarbonate resins, acrylic resins, polyacrylamide resins, polyvinyl chloride resins, polyvinylidene resins, polystyrene resins, polyvinyl acetate

resins, vinyl chloride vinyl acetate copolymer resins, silicone resins, phenolic resins, phenoxy resins, melamine resins, benzoguanamine resins, urea resins, polyurethane resins, poly-N-vinylcarbazole resins, polyvinyl anthrathene resins, polyvinylpyrene resins, polyether resins, polyvinylsulphone resins, polyketone resins and especially polycarbonate resins such as poly (4, 4'-isopropylidene diphenylene carbonate) such as those commercially available under the trade name Lexan, Makrolene and Marlon, bis- phenol-A-polycarbonate and poly (4, 4'-cyclohexylidene diphenylene carbonate). Preferred binder resins are electroreprographically inert and are more preferably electrical insulators and preferably have a number average molecular weight (Mn) from about 20, 000 to 120, 000 daltons and especially from about 50, 000 to about 100, 000 daltons.

The amount of CGM to binder resin in the CGL is preferably from 5 : 1 to 1 : 2 by volume.

Suitable organic liquids which may be used to prepare the CGL include aliphatic alcohols such as methanol, ethanol, n-propanol, n-butanol ; benzyl alcohol ; methyl cellosolve ; ethylcellosolve ; ketones such as acetone, methylethylketone and cyclohexanone, aromatic solvents such as xylene and toluene ; cyclic ethers such as tetrahydrofuran, esters such as ethylacetate and butylacetate and aliphatic and aromatic chlorinated hydrocarbons such as chlorobenzene, dichloromethane and dichloroethane, including mixtures thereof.

The liquid coating used to prepare the CGL may be applied by any method known to the art such as blade coating, spin coating, Meyer bar coating, spraying, immersion coating, bead coating, air knife coating and curtain coating. The thickness of the CGL is preferably from 0. 01 to 5 m and especially from 0. 1 to 2. 0 m.

The amount of Polymeric material in the CTL is preferably from 5 : 1 to 1 : 1 by volume. The CTL may be prepared in similar manner to that described above relating to the CGL, especially using a liquid coating as described for the CGL. The thickness of the CTL is preferably from 5 to 70 lim and especially from 10 to 50 m.

The CTL may additionally contain other adjuncts such as a photostabiliser and/or electron acceptor.

Examples of photostabilisers are derivatives of benzophenone, benzotriazole, dithiacarbamate and tetramethylpiperidine.

Examples of electron acceptors are succinic anhydride, maleic anhydride, dibromomaleic anhydride, phthalic anhydride, tetrabromophthalic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, chloranyl, dinitroanthraquinone, trinitrofluorenone, picric acid, o-nitrobenzoic acid, p- nitrobenzoic acid and phthalic acid.

Other additives include plasticisers and silicone oils such as halogenated paraffin, polybiphenyl chloride, dimethylnaphthalene, esters of dibasic, organic acids such as dibutylphthalate, dioctylphthalate, dioctylsebacate and dihexyladipate, alkyl-modified

silicone oils such as dimethylsilicone oil and aromatic modified silicone oils such as methylphenylsilicone oil. The amount of plasticiser or silicone oil in the CTL is preferably from 1 to 10, 000 ppm and especially from 5 to 2, 000 ppm.

As noted hereinbefore, the CTL and CGL may also be combined in a single layer wherein the amount of CGM to Polymeric Material (CTM) is preferably from 0. 1 to 20% by weight and especially from 0. 5 to 5% by weight. The thickness of this single layer is preferably from 5 to 70 m and especially from 10 to 40 Vim.

As noted hereinbefore, the Polymeric Material may be used as a CTM in electro reprographic devices. However, the Polymeric Material may also be useful in other electronic devices such as electro luminescent (EL) devices, organic light-emitting devices (OLED) (e. g. devices where the organic light emitting material (OLEM) comprises a light-emitting polymer (LEP) and/or devices which comprise light-emitting diodes (LED) ; semi conductor devices ; photo conductive diodes ; metal-semiconductor junctions (e. g.

Schottky barrier diodes) ; p-n junction diodes ; solar cells and/or batteries ; photovoltaic devices (e. g. photovoltaic cells) ; photodetectors, optical sensors ; phototransducers ; bipolar junction transistors (BJTs), heterojunction bipolar transistors and/or other switching transistors ; field effect transistors (FETs) (which may comprise metal- semiconductor FETs, metal-insulator-semiconductor FET's and/or organic FETs) ; charge transfer devices (which may comprise charge coupled devices [CCDs]) ; lasers (which may comprise semiconductor and/or organic lasers) ; p-n-p-n switching devices (which may comprise semiconductor controlled rectifiers [SCRs)] ; optically active EL devices (which for example may be prepared by control of homochiral monomer polymerisation to achieve polarised light output, e. g. for 3-D imaging) ; thin film transistors (TFT, e. g. polymeric TFTs) ; organic radiation detectors ; infra-red emitters ; tunable microcavities for variable output wavelength ; telecommunications devices and applications (for example a combination of ILEM, fibre optic and detector) ; optical computing devices (especially using materials with improved switching speeds) ; optical memory devices (for example devices which rely on external stimulus to trigger EL emission for devices run just below threshold onset voltage) ; general design of detectors and/or sensors (for example by combining EL excitation just below onset voltage, relying on external stimulation to trigger EL emission) ; chemical detectors (e. g. by combining EL with known or future luminescence detector systems) ; and combinations of any such devices and/or applications in which they are used.

The invention is further described by the following non-limiting examples, wherein all references are to parts by weight unless stated to the contrary.

Test Method 1 Measurement of Photo-Induced Decay Curves (PIDC) A electrophotographic photoreceptor was prepared as described below using the CGL prepared using Test Method 1. 1 for CTL's according to the present invention or Test Method 1. 3 for prior art CTL's 1. 1 Preparation of Charge Generation Layer (CGL) Titanyloxy phthalocyanine (TiOPc) type IV (15. 0 parts) was dispersed into a 5% w/w solution of polyvinyl butyral (PVB) in n-butyl acetate (75. 0 parts) using a high shear mixer. A further quantity of n-butyl acetate (20. 0 parts) was added to the dispersion to reduce its viscosity. The resulting millbase was charged to an Eiger Mini 50 Motormill (supplied by Eider Torrance Ltd) containing a charge (34 ml) of 0. 6 to 0. 8 mm zirconia beads. The mill was operated at 3, 000 rpm for 50 minutes. PVB solution (25. 0 parts, 5% w/w in n-butyl acetate) was added to the millbase and milling was continued for a further 10 minutes. The millbase was discharged into receiving vessel and PVB solution (61. 5 parts) was added to the mill and circulated for 5 minutes. The solution was then discharged into the millbase which was stirred throughout to prevent pigment agglomeration and n-butyl acetate (349. 0 parts) was flushed through the bead mill and out into the stirred dispersion to yield a CGL coating formulation of PVB (1. 48%), TiOPc (2. 75%) and n-butyl acetate (95. 77%).

The dispersion was coated onto aluminised Melinex film using a K#2 bar and K Control coater model 202 (supplied by RK Print-Coat Industries Ltd). The coating was dried for 5 minutes at 100°C to produce a CGL which was approximately 0. 4 m thick.

1. 2 Preparation of a Charge Transport Layer (CTL) according to the invention A formulation comprising the Polymeric Material was prepared using an amount of the Polymeric Material and (optionally) another CTM as specified below (e. g. in the Tables). If not otherwise specified herein 0. 5 parts of CTM was used (equivalent to 25% CTM in the CTL) in the following preparation. The Polymeric Material and polycarbonate resin 1. 5 parts of the PCZ available commercially from Esprit Chemical Co. (under the trade designation TS 2020) were dissolved in toluene (7. 1 parts). This solution was coated on top of the CGL made as described above, using a 150 nm wet film depositing bar and K Control coater. The coating was dried for 90 minutes at 100° C to give a CTL which was approximately 25 m thick. The CTL thickness was measured using an Elcometer E 300 device.

1. 3 Preparation of prior art comparative CTL The following coating solution was prepared as a comparison using the well- known CTM : bis (N, N'-3-methylphenyl) bis (N, N'-phenyl)-1, 1'-(biphenyl) 4, 4'-diamine (TPD) TPD (3. 3 parts), PCZ (5. 0 parts) and tetrahydrafuran (THF, 29. 5 parts) were mixed

together to form a solution. This solution was coated on top of the CGL prepared as described above, using a 150 m wet film depositing bar and K Control coater. The coating was dried for 90 minutes at 100°C to give a CTL which was approximately 25 pm thick. The CTL thickness was measured using an Elcometer E300 device. The CTL comprised 40% CTM. A comparative device was freshly prepared for testing with each series of polymeric CTM samples.

1. 4 Electrical testing to evaluate photo-induced discharge curves (PIDC) A photoreceptor test piece of approximately 5 x 10 cm was cut out from the coated aluminised Melinex prepared as described above. The test piece was then fixed to a bare aluminium drum (used as the substrate for an OPC), 30 mm in diameter. Two small areas of coating were removed from the edge of the test piece using a suitable solvent.

The test piece was then electrically connected to the drum using a suitable conductive paint. The drum was then mounted in a QEA PDT 2000 device (available commercially from Quality Engineering Associates Inc. Burlington MA 01803 USA) and was grounded via the contact in the QEA instrument. The QEA PDT 2000 was fitted with a 780nm band pass filter. A track with a consistent 800 V charge of at least 10 mm length was selected using a charge scanner. Once the track had been selected the PIDC was measured in the known manner. The surface potential VO (V), the half decay exposure E"2 (Jcm-2) and the seven eighths decay exposure E7, 8 (pJcm~2) were measured together with the residual potential Vr, (V) after an exposure of 2 pJcm~2. Low values for E"2, E7, and Vr, are desirable in a CTM as they indicate efficient discharge of the device on exposure to light.

The reliability of the test method and accuracy of the equipment was checked by testing a freshly prepared comparative CTL (fabricated as described in Test Method 1. 3) for each measurement.

Test Method 2 Time of flight (TOF) experiment to measure zero field mobility (no) A number of electrophotographic photoreceptors were prepared in a similar manner to that described above for the PIDC experiments.

2. 1 Preparation of CGL The method described above (in Test Method 1. 1) was used to prepare a CGL The CGL layer promotes adhesion of the CTL to the substrate and may also be used to generate carriers during the TOF measurement.

2. 2 Preparation of CTL The method described above (in Test Method 1. 2 and Test Method 1. 3) for preparation of both invention and comparative CTLs, was followed. If otherwise not stated a 25% concentration (by mass) of CTM was used to 75% PCZ in the solid CTL.

2. 3 Electrodinq A semi-transparent aluminium electrode of approximately 6 mm diameter was applied to the top of a section of the film by vacuum deposition. A small portion of the CGL and CTL (prepared as described above) close to the top electrode, was removed with a suitable solvent to reveal the bottom electrode. The electrodes were connected to a power supply and a digitising oscilloscope.

2. 4 Hole carrier transit-time measurement A field was applied across the sample via the electrodes and a sheet of charge carriers (holes) was photogenerated at one side of the film. The charge carriers drifted through the film under the influence of the field creating a current which was detected using a current amplifier connected to the oscilliscope. When the carriers reached the counter electrode, the current was observed to decrease and the transit-time across the film could thereby be determined from the transit waveform. The measurement was repeated with a range of different applied voltages.

2. 5 Determination of zero field mobilitv (Lo) The drift mobility of carriers () was calculated for each applied field (= V/L) using the equation : L'/V ttr' where L is the device thickness, V is the applied voltage and ttr is the transit time. A plot of log versus (V/L)'was produced with a best line fit. The best line fit was extrapolated to zero field and jlo determined.

Preparation of Photoreceptor Drum A 30 mm diameter aluminium cylinder drum pre-coated with a titanyloxy phthalocyanine (TiOPc) CGL layer was used as substrate. The CGL coating can be prepared as disclosed in WO 99/32537.

A CTL solution was prepared by dissolving 17 parts solid material in 83 parts tetrahydrofuran by weight. The dissolved solids comprised of 20-40wt% charge transport material (CTM) the remainder being 80-60wt% polymeric binder e. g. polycarbonate Z (PCZ-as TS 2020). In some cases a small amount of additive was added to the solution.

The solution was coated on top of the CGL by dipping. The coating was dried for 90 minutes at 100 °C to give a CTL which was approximately 25 vim thick as measured using an Elcometer E 300 meter.

Test Method 3 The print quality of the photoreceptor was evaluated in a Hewlett-Packard Laserjet 5 printer. The photoreceptor was fitted in a toner cartridge and test pages were printed.

The test image pattern was generated by an Anacom Analyser (Anacom Corporation,

Anaheim, CA). These images included halftone, solid black, white, text and graphical test images. Photoreceptors often suffer from image deletion after printing a number of pages. This manifests itself in image blurring, the characters becoming thinner or wide lines thicker. In the current test the image blurring was detected on halftone (grayscale) images. The extent of image blurring was recorded after every thousand pages. The image degradation was recoverable i. e. after resting the photoreceptor the image quality returned to its original.

Test Method 4 In order to accelerate image deletion, the photoreceptor was"parked"under the corona charger of a PDT2000 (Burlington MA) electrophotographic test instrument. The corona device was set to 7kV or 8 kV and left on for 15 or 30 minutes. Effluents emitted by the corona attack the photoreceptor surface and lead to image degradation. After exposure to corona, the photoreceptor was fitted in a cartridge and test pages were printed as described in Test Method 3. The image blurring appeared in a round area resembling the shape of the corona charger. The extent of the degradation could be judged by the size of the area affected and the quality of the image. After resting the photoreceptor the original image quality was restored. The time required to complete recovery of the photoreceptor was also recorded.

Example 1 a) Preparation of bis (N-4-chlorophenvl)-2, 4-dimethylphenvlamine (Monomer 1) This was prepared by the method described in Example 3a of WO 99/32537 and was recrystallised from n-butanol. b) Polymerisation of Monomer 1 in the presence of 4-bromo-2. 6-di-tert-butylphenol.

A 500 ml flask was flame-dried under nitrogen and charged with anhydrous N, N- dimethylacetamide (122. 7 parts ex Aldrich) via a Sureseal bottle equipped with a canula.

The zero-valent nickel catalyst was prepared by adding nickel chloride (0. 10 parts, 0. 78 mM ex Aldrich), (2, 2-bipyridine (0. 194 parts, 1. 24 mM ex Aldrich), zinc powder (7. 07 parts, 108 mM ex Aldrich) and triphenylphosphine (2. 04 parts, 7. 78 mM ex Aldrich) under nitrogen and stirred at 76°C whereupon a dark red colour developed indicating the formation of the zero-valent nickel complex. Monomer 1 (12. 5 parts ; 36. 55 mM) was added followed by the dropwise addition over two hours of a solution of 4-bromo-2, 6-di- tert-butylphenol (3. 13 parts 11. 0 mM ex Aldrich) and Monomer 1 (1. 5 parts, 4. 39 mM) in N, N-dimethylacetamide (24 parts) whilst stirring under nitrogen at 76-82°C. After stirring for a further three hours, nickel chloride (0. 05 parts ; 0. 39 mM), 2, 2-bipyridine (0. 097 parts, 0. 62 mM), zinc powder (3. 54 parts, 54 mM) and triphenylphosphine (1. 02 parts, 3. 89 mM) were added followed by the dropwise addition over 2 hours of a further solution of

4-bromo-2, 6-di-tert-butylphenol (2. 08 parts, 7. 3 mM), Monomer 1 (1. 0 parts, 2. 92 mM) in N, N-dimethylacetamide (16 parts). The reactants were stirred at 76-82°C under nitrogen for a further 16 hours and 4-bromo-2, 6-di-tert-butylphenol (10. 42 parts, 36. 55 mM) were added and stirred at 76-82°C for a further 6 hours.

The reactants were then cooled to 25°C, diluted with water (164. 5 parts) and concentrated hydrochloric acid (22. 2 parts) was added to destroy the zinc powder. The polymers were extracted into dichloromethane (94. 8 parts), washed with 10% aqueous sodium carbonate (155 parts), followed by water (155 parts).

The dichloromethane was then removed under reduced pressure and the residual solids were dissolved in tetrahydrofuran (31. 6 parts) and reprecipitated by drowning into methanol (169. 6 parts) to give a greenish-yellow powder (11. 6 parts).

The powder was dissolved in a 2 : 1 mixture of dichloromethane/hexane (80 mis) and passed down a silica column (100 parts). Two yellow fractions were obtained by elution using a 60/40 mixture of dichloromethane/hexane. The solvent mixture was removed under reduced pressure and the solids separately dissolved in tetrahydrofuran (40 mis) and reprecipitated by drowning into methanol (250 ml).

Solid I, pale yellow solid, 6. 0 parts Mn = 2295, average number of triphenylamine repeat units = 8. 5 ; and Solid II, yellow solid, 3. 3 parts, M = 1868, average number of triphenylamine repeat units = 6. 9.

These two solids were combined (9. 3 parts), Mn = 2182, Mw = 4264, polydispersity = 1. 95, average repeat units = 8. 0. HPLC analysis suggests that about 20% of the terminal groups are 2, 6-di-tert butyl phenol. This is CTM 1.

Test Results PIDC data was determined for CTM 1 using the Test Protocol described hereinbefore. The results are given in Table 1 below.

Table 1 SAMPLE VO E 1/2 E 7/8 Rp DARK Thickness volts (pJ/cm2 (pJ/cm2) volts DECAY (jl) CTM 1 801 0. 057 0. 182 10 15. 7 30. 0 CONTROL 799 0. 051 0. 234 39 6. 9 28. 5 Footnote to Table 1 Control is bis (N, N'-3-methylphenyl) bis (N, N'-phenyl)-1, 1'-biphenyl-4, 4'-diamine (TPD)

Example 2 Print-Life Quality The print-life of CTM 1 was determined according to Test Method 3 as described hereinbefore under the legend Test Protocols. The results are given in Table 2 below.

CTM 1 exhibits significantly better print-life compared with the CTM of WO 99/32537.

Table 2 Example/1000 2000 3000 4000 Comparative Example CTM ADDITIVE PAGES PAGES PAGES PAGES 2 CTM 1 A N * ** *** A 2, 4 dimethyl oligomer B 2, 4 dimethyl 0. 05% ODHP oligomer ** C 2,4 dimethyl 0.15% ODHP oligomer Footnote to Table 2 2, 4-dimethyl oligomer is the CTM of Example 3 (b) in WO 99/32537 ODHP is octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ex Ciba-Geigy (Irganox 1076) N no image deletion * mild considerable *** strong **** very strong Example 3 image Deletion The image deletion of CTM's was determined according to Test Method 4 of the Test Protocols. The results are recorded in Table 3 below. These data show that CTM exhibits greater tolerance to image deletion and significantly faster recovery time compared with the CTM of WO 99/32537.

Table 3 EXAMPLE/CORONA COMPARATIVE CTM ADDITIVE PARKING IMAGE RECOVERY EXAMPLE (MINS) DELETION TIME 3 CTM1 - 7kV 15 * 45 mins D 2, 4 dimethyl 2-4 oligomer 7kV 15 *** hours E 2, 4 dimethyl 0. 15% ODHP oligomer 7kV 15 *** >3 hours F 2, 4 dimethyl 0. 3% ODHP oligomer 7kV 15 *** 2-4 hours G 2, 4 dimethyl 0. 3% ODHP oligomer 0. 6% TTBP 7kV 15 *** 2 hours H 2, 4 dimethyl 0. 3% ODHP oliomer 1. 2% TTBP 7kV 15 *** 1. 5 hours 2, 4 dimethyl 0. 38% ODHP oligomer 0. 52% TTBP 7kV 15 *** 1. 5-2 hours

Footnote to Table 3 2, 4-dimethyl oligomer is the CTM of Example 3 (b) in WO 99/32537 ODHP is octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ex Ciba-Geigy (Irganox 1076) TTBP is tris (2, 4-di-tert-butylphenyl) phosphite ex Ciba-Geigy (irgafos 168) * and *** are as explained in the footnote to Table 2.

Example 4

a) Preparation of 4-bromo-2, 6-di-tert butylphenol trimethyl silyl ether A 500 ml flange flask was flame dried under nitrogen. The flask was then charged with 4-bromo-2, 6-di-tert butylphenol (57 parts, ex Aldrich) and dry acetonitrile (300 ml) under nitrogen. N, O-Bis- (trimethylsilyl) acetamide (41 parts, ex Aldrich) was added to

the flask via a pressure equalised dropping funnel whilst stirring under nitrogen.

Approximately 10% of the acetamide was added at 25°C and the temperature raised to 75°C. The remainder of the acetamide was added dropwise over 30 minutes with stirring under nitrogen at 75-80°C. The resulting clear yellow solution was stirred at 80-82°C under nitrogen for a further 51/2 hours. The reaction mix was then cooled to 25°C and the product filtered, washed with dry acetonitrile and dried under vacuum at 60°C. Yield (64. 9 parts).

Proton NMR analysis :- 7. 1ppm (2H, aromatics) ; 1. 2 ppm (18H, singlet, tert-butyl) and 0. 2ppm (9H ; singlet ; CH3 Si). b) Polymerisation of Monomer 1 in the presence of protected phenol from (a) above.

Zero valent nickel catalyst was prepared under nitrogen as described in Example 1 (b) except using nickel chloride (0. 388 parts), zinc powder (23. 64 parts), triphenyl phosphine (15. 72 parts) and 2, 2-bipyridine (0. 79 parts) but using dimethylformamide (300 ml) as solvent in place of the dimethylacetamide. The reactants were stirred under nitrogen at 70°C when the reaction mix developed a dark red colour indicating the formation of the zero-valent nickel catalyst. Monomer 1 (40 parts ex Example 1 (a)) was added to the catalyst solution. The protected phenol (42 parts, ex Example 2 (a)) was dissolved in toluene (100 ml) and added dropwise to Monomer 1 with stirring under nitrogen at 70°C over 2Y2 hours. Aliquots were analysed periodically by HPLC. Further quantities of the protected phenol were added after 3 hours (10. 5 parts), 4 hours (5. 5 parts) and 5 hours (5. 5 parts) dissolved in toluene. Finally, the reactants were stirred under nitrogen at 70°C for a further 16 hours.

The reactants were then cooled to 25°C, dichloromethane (1000 ml) added followed by the dropwise addition of 36% (""/W) hydrochloric acid (200 ml) to destroy excess zinc. The organic layer was separated and washed sequentially with distilled water (50 ml), saturated sodium bicarbonate solution (500 ml) and distilled water (500 ml).

The organic layer was then dried over anhydrous magnesium sulphate, filtered and the dichloromethane removed under vacuum to leave a dark red viscous liquid. This was dissolved in tetrahydrofuran (250 ml), filtered and added dropwise to methanol (1000 ml) with stirring at 25°C whereupon the polymer separated as a yellow powder (49. 3 parts).

This was washed with methanol and dried under vacuum at 60°C. The polymer was then purified using a silica gel column with dichloromethane as eluent. Finally, the polymer was again dissolved in tetrahydrofuran (150 ml) and re-precipitated by dropwise addition to methanol (600 ml). The polymer was obtained as a pale yellow powder (39. 6 parts).

c) Removal of trimethylsilyl protective end-group The polymer from (b) above (39. 6 parts) was dissolved in tetrahydrofuran (400 ml), cooled to 0°C and tetrabutylammonium fluoride (1 part ex Aldrich) dissolved in tetrahydrafuran (20 ml) added dropwise whilst stirring at 0°C. The reaction was continued by stirring for 16 hours allowing the temperature to rise to 25°C. This reaction mix was then added dropwise the methanol (1600 ml) with stirring at 25°C whereupon the polymer separated as a yellow solid (35. 5 parts). This was purified by column chromatography using a silica gel column developed with a 1 : 1 mixture of dichloromethane and hexane.

The polymer was again dissolved in tetrahydrofuran (250 ml) and precipitated by addition to methanol (1000 ml). This purification by column chromatography and precipitation from tetrahydrofuran was repeated to give a pale yellow powder (22. 5 parts). This is CTM 2.

The number average molecular weight (Mn) is 3000 wherein the number of repeat triphenylamine units is 10. 7. HPLC analysis indicates about 90% of the terminal groups in the polymeric mixture are 2, 6-di-tert butylphenol groups.

Test Results PIDC data was measured for CTM2 using the Test Protocol described hereinbefore. The results are given Table 4 below Table 4 Sample VO E.,, E, Rp DarkThickness volts (fiJ/cm) (J/cm) volts Decay CTM2 800 0. 149 0. 319 7. 1 14. 3 27. 4 Control 801 0. 160 0. 375 27. 8 10. 9 28. 0 Footnote to table 4 Control is bis (N, N'-3-methylphenyl) bis (N, N'-phenyl)-1, 1-biphenyl-4, 4'-diamine (TPD) The print-life quality is assessed as N (no image deletion) after 1000 and 2000 pages and (mild image deletion) after 3000 and 4000 pages.

The image deletion after 15 minutes corona parking at 7KV was assessed as very slight trace of spread and is superior to CTM1.

Example 5

a) Preparation of N, N-bis (4-chlorophenyl)-4-boronic acid anilide N, N-bis (4-chlorophenyl)-4'-bromoaniline (57. 5 parts, ex) was dissolved in tetrahydrofuran (600 ml) and cooled to-74°C (carbon dioxide in methanol). A solution of n-butyllithium in hexane (60. 83 parts as 2. 5 M solution ex Aldrich) was added dropwise with stirring at-74°C over 30 minutes. After stirring for a further 30 minutes, trimethylborate (66. 5 ml, ex Aldrich) was added dropwise with stirring and the reactants were stirred at-70°C for 1 hour followed by stirring for a further 16 hours when the temperature was allowed to rise to 25°C. The reaction mixture was then concentrated and dissolved in dichloromethane (500 ml). This solution was washed with 2M hydrochloric acid (4 x 100 ml), dried over anhydrous magnesium sulphate and filtered. On concentrating to 200 ml, the product separated as a white solid (19 parts). Further product (3. 98 parts) was obtained by further concentration. These solids were dissolved in toluene (800 ml) and stirred for 16 hours at 25°C with 2M hydrochloric acid (400 ml).

The organic layer was separated and the toluene removed by vacuum distillation to give a white powder (20. 86 parts) which was washed with acetone and dried. b). Preparation of the hindered phenol analogue of (a) The reaction product from stage (a) above (20. 85 parts,), 4-trimethylsilyloxy- 3, 5-di-tert-butylbromobenzene (20. 80 parts, ex Aldrich) and 2M sodium carbonate solution in water (200 ml) were stirred together at reflux for 19 hours. After cooling to 25°C, the product was extracted into toluene (100 ml), washed with water (4 x 100 ml) and dried over anhydrous magnesium sulphate. The toluene was removed to leave a green residue (37. 42 parts). This was subjected to flash column chromatography on a silica column developed using hexane. The resulting material (11. 3 parts) contained a mixture of monomers, one being the de-protected phenol and the other being the trimethyl silyloxy analogue.

This mixture was subjected to reprotection of the phenol using N, O-bis- (trimethylsilyl) acetamide (BSA). The mixture (11. 3 parts) was dissolved in a mixture of acetonitrile (50 ml) and tetrahydrofuran (50 ml) and a solution of BSA (4. 43 parts, ex Aldrich) dissolved in acetonitrile (30 ml) was added dropwise with stirring at 25°C. The reactants were then stirred at reflux for 19 hours and a further aliquot of BSA (2. 20 parts) was added and the reaction continued for a further 11/2 hours. After cooling to 25°C, methanol (100 ml) was added whereupon the product separated as a white solid. This was separated, washed with methanol and re-crystallised from n-butanol to give a white solid (7. 08 parts).

This monomer was prepared by the method described in Chem. Review, 1995, 95, pages 2457-2483. c) Polymerisation of monomer from stage (b) Zero-valent nickel catalyst was prepared from zinc powder (0. 691 parts, 100 mesh ex Aldrich), nickel (II) chloride (0. 011 parts ex Aldrich), triphenylphosphine (0. 453 parts ex Aldrich), 2, 2'-dipyridyl (0. 02 parts ex Aldrich) and dimethylacetamide (20 ml) by stirring at 25°C for 10 minutes followed by stirring at 80°C for 15 minutes. Development of a deep red colour indicated formation of the catalyst.

The protected monomer from stage (b) (2 parts) was added and the reactants were stirred at 80°C for 6 hours. This was followed by 3-chlorotolune (0. 644 parts) and the reaction was continued at 80°C for 16 hours to terminate the polymerisation and end- cap the polymer chains. During this reaction the red colouration faded indicating loss of catalyst. Consequently, two further aliquots of nickel (II) chloride (2 x 40 mg) were added to regenerate the catalyst followed by the addition of more 4-chlorotoluene (0. 644 parts).

The reaction was continued by stirring for a total of 47 hours at 80°C. After cooling to 25°C toluene (10 ml) was added followed by concentrated hydrochloric acid (15 ml) to destroy remaining zinc. Further toluene (50 ml) was added and the organic layer was separated and washed successively with water (35 ml), 2M sodium bicarbonate solution in water (35 ml) and saturated brine (35 ml). After drying over anhydrous magnesium sulphate, the toluene was removed under vacuum leaving a yellow oil (1. 64 parts). This was dissolved in tetrahydrofuran (15 ml) and the solution added dropwise to methanol (45 ml) whereupon the polymer separated as a yellow powder (1. 32 parts). This was dissolved in dichloromethane (7 ml) and hexane (7 ml) was added. This solution was added to a silica column and developed with a 3 : 1 mixture of dichloromethane and hexane. After evaporation of the solvent the polymer was obtained as a yellow solid (1. 25 parts). This was further purified by dissolving in tetrahydrofuran (15 ml) and re- precipitated by adding to methanol (45 ml). Yield of yellow polymer was 0. 82 parts.

d) Deprotection of polymer from stage (c) by removing the trimethylsil rl rq oup.

The polymer from stage (c) above (0. 82 parts) was dissolved in tetrahydrofuran (10 ml), cooled to-10°C and a solution of tert-butyl ammonium fluoride (1. 72 parts) in tetrahydrofuran (5 ml) was added with stirring. The reactants were stirred for 16 hours allowing the temperature to rise to 25°C. This was then poured into methanol (60 ml) with stirring when the polymer separated as a pale lime green solid (0. 658 parts). This was purified by dissolving in dichloromethane (6 ml) and separated on a silica column developed using a 3 : 1 mixture of dichloromethane and hexane. After removing the solvent, the residue was dissolved in tetrahydrofuran (11 ml) and the polymer precipitated by adding to methanol (30 ml). The polymer was obtained as a pale lime green solid (65 mg). This is CTM3.

This polymer exhibited a number average molecular weight (Mn) of 4100 indicating an average number of repeat triphenylamine units of 8. 8. HPLC analysis indicated that 75% of the end-cap units were 3-totyl groups.

Test results The PIDC data was measured for CTM3 using the Test Protocol described hereinbefore. The results are given in Table 5 below.

Table 5 Sample Vo E, E7/8 Dark Thickness volts (VLJ/CM') (lJ/cm2) volts Decay CTM3 798 0. 169 0. 390 40. 8 12. 8 27. 6 Control 800 0. 156 0. 474 62. 3 6. 0 30. 2 Footnote to Table 5 Control is as described in the footnote to Table 4.