CARBAZOLYL MONOMERS AND POLYMERS

BACKGROUND

[0001] The invention relates generally to compounds comprising carbazole units that are difunctional. The invention also relates to monomers comprising carbazole units and polymers, dendrimers, and hyper-branched materials derived therefrom.

[0002] Organic light emitting devices (OLEDs), which make use of thin film materials that emit light when subjected to a voltage bias, are expected to become an increasingly popular form of flat panel display technology. This is because OLEDs have a wide variety of potential applications, including cellphones, personal digital assistants (PDAs), computer displays, informational displays in vehicles, television monitors, as well as light sources for general illumination. Due to their bright colors, wide viewing angle, compatibility with full motion video, broad temperature ranges, thin and conformable form factor, low power requirements and the potential for low cost manufacturing processes, OLEDs are seen as a future replacement technology for cathode ray tubes (CRTs) and liquid crystal displays (LCDs). Due to their high luminous efficiencies, OLEDs are seen as having the potential to replace incandescent, and perhaps even fluorescent, lamps for certain types of applications.

[0003] One approach to achieve full-color OLEDs includes energy transfer from host to emissive guest molecules. For this to be realized, the triplet energy state of the host has to be higher than the guest molecule. Carbazole derivatives have shown promise to perform well as host molecule in the presence of metal containing emissive guest molecules. Often used in this respect is poly(N-vinyl carbazole). However, quantum efficiencies of devices that use poly(N-vinyl carbazole) is still at the range of about 60 to 80%. Thus, there is a need in the art to develop OLEDs having device quantum efficiencies, while still maintaining the potential for the molecules to host red, green, and blue emissive complexes.

BRIEF DESCRIPTION

[0004] In one aspect, the invention provides a compound of formula I

Formula I

wherein R is H or alkyl;

R ¹ , R ² , and R ⁴ are independently at each occurrence a C1-C20 aliphatic radical, a C3- C ₂₀ aromatic radical, or a C ₃ -C ₂₀ cycloaliphatic radical; R ³ and R ⁵ are independently at each occurrence hydrogen, a C1-C20 aliphatic radical, a C3-C20 aromatic radical, or a C3-C20 cycloaliphatic radical; and

a, b and d are independently 0 or an integer ranging from 1 to 3.

[0005] In another aspect, the invention provides a polymer comprising structural units of formula II

Formula II

wherein R ¹ , R ² , and R ⁴ are independently at each occurrence a C1-C20 aliphatic radical, a C3-C20 aromatic radical, or a C3-C20 cycloaliphatic radical; R ³ and R ⁵ are independently at each occurrence hydrogen, a C ₁ -C ₂₀ aliphatic radical, a C ₃ -C _2O aromatic radical, or a C3-C20 cycloaliphatic radical; a, b and d are independently 0 or an integer ranging from 1 to 3.

[0006] In yet another aspect, the invention provides a light emitting device comprising at least one electrode, at least one hole injection layer, at least one light emissive layer; wherein the light emissive layer comprises a polymer comprising structural units of formula II.

DRAWINGS

[0007] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0008] FIG. 1 Time resolved photo luminescence spectra of device comprising polymer from Example 6 (dotted lines) and device comprising polystytrene (solid line).

[0009] FIG. 2: Time resolved photoluminescence spectra of device comprising poly(N-vinyl carbazole) (dotted line) and device comprising polystytrene (solid line).

DETAILED DESCRIPTION

[0010] In one aspect, the invention provides a compound comprising carbazole units having formula I. Compounds of formula I may generally be regarded as carbazole compounds. In some cases, the 3, -6 positions may be susceptible to oxidative coupling reactions, and it may be advantageous to protect one or more of these positions. Thus, in some embodiments, R ³ and R ⁵ are hydrogens, thus the carbazole units are unprotected at the 3 and 6 positions. In some other embodiments, R ³ and R ⁵ are t-butyl groups, while in still other embodiments, R ³ and R ⁵ are trialkylsilyl and triarylsilyl groups, and in yet other embodiments, they are diphenyl phosphine oxide or diphenyl phosphine sulfide. A wide variety of other groups may also be used to substitute the carbazole at the 3 and 6 positions, and these may include, but not limited to, methyl, ethyl, methoxy, tolyl, methylcyclohexyl, and halomethyl. In a particular aspect, the invention relates to a monomer of formula I, wherein b and d are 0, which has formula

[0011] The present invention relates to carbazole compounds that are N-substituted with an aromatic group of formula

wherein R, R ¹ and a are as defined before. The aromatic groups may be attached to the carbazole units by the reaction of an appropriate aromatic halide with carbazole to obtain the product in high yields. The reaction may be conducted in an inert solvent, and optionally, in the presence of catalysts.

[0012] In one aspect, the invention provides a compound of formula I, wherein R is an alkyl group. Thus, in one exemplary embodiment, R is a methyl group, a, b and d are all 0, the alkoxy groups are present on the 3 and 5 positions, and the resulting compound is 9-(3,5-dimethoxyphenyl)carbazole of formula

[0013] In another aspect, the invention provides a compound of formula I, wherein R is an alkyl group. Thus, in one exemplary embodiment, R is a methyl group, a, b and d are all 0, the alkoxy groups are present on the 2 and 5 positions, and the resulting compound is 9-(2,5-dimethoxyphenyl)carbazole of formula

[0014] In another aspect, the invention provides a monomer of formula I, wherein R is a hydrogen, and the resulting compound is a dihydroxy functional compound. The hydroxyl groups may be present on any of the positions on the phenyl ring, for example on the 3 and 5 positions or the ortho and meta positions with respect to the position of the carbazole unit. In one particular instance, when R is a hydrogen, a, b and d are all 0, the compound is 9-(3,5-dihydroxyphenyl)carbazole of formula

[0015] In yet another aspect, the invention provides a monomer of formula I, wherein R is a hydrogen, and the resulting compound is a dihydroxy functional compound. The hydroxyl groups may be present on any of the positions on the phenyl ring, for example on the 2 and 5 positions or the ortho and meta positions with respect to the

position of the carbazole unit.. In one particular instance, when R is a hydrogen, a, b and d are all 0, the compound is 9-(2,5-dihydroxyphenyl)carbazole of formula

[0016] The compounds of the present invention are particularly well suited for use in hole transport layers in organic light emitting devices. In one embodiment, the present invention provides an organic light emitting device comprising a hole transport layer which consists essentially of the compounds. In another embodiment, the present invention provides an organic light emitting device comprising the compounds as a constituent of a hole transport layer of an organic light emitting device.

[0017] In another aspect, the present invention relates to polymers having structural units of formula II. The polymers are prepared by copolymerizing one or more monomers of formula I with one or more comonomers to result in polycarbonates, copolycarbonates, polyarylates, copolyarylates, copolyestercarbonates, polyethers, polyether sulfones, polyether imides, and combinations thereof, in the form of random, block, or graft copolymers, or dendrimers or hyper-branched materials.

[0018] Accordingly, in some embodiments, the monomer of formula I may be copolymerized with phosgene, or phosgene and a bisphenol, or with a diaryl carbonate or bishaloformate to provide a polycarbonate. Exemplary monomers to make polycarbonates include diphenyl carbonate, bis(methylsalicyl) carbonate, bisphenol A bischloroformate, resorcinol bischloroformate, and combinations thereof.

For example, copolymerization with phosgene and bisphenol A results in a polymer comprising structural units of formula

in addition to the structural units of formula II. Thus, in one particular embodiment, the resulting polymer comprises structural units of formula

For example, a monomer of formula I may be reacted with bisphenol A and diphenyl carbonate in the presence of a minute amount of a basic catalyst such as sodium hydroxide at a temperature in a range between about 150 and 300 ⁰ C at subatmospheric pressure.

[0019] In other embodiments, the monomer of formula I may be copolymerized with a carboxylate ester, a carboxylic anhydride, or a carboxylic acid halide to yield a polyester. Exemplary comonomers that may be used to make polyesters include terephthaloyl chloride, terephthalic anhydride, naphthoic dianhydride, succinic anhydride, dimethyl oxalate, and combinations thereof.

[0020] In yet other embodiments, the monomer of formula I may be copolymerized with one or more dihaloarylsulfone monomer to yield a poly ether sulfone. Dihaloarylsulfones may include bis(4-fluorophenyl)sulfone, bis(4- chlorophenyl)sulfone, 4,4' -bis((4-chlorophenyl)sulfonyl)- 1 , 1 -biphenyl and combinations thereof.

[0021] In other embodiments, the monomer of formula I may be copolymerized with one or more dihaloaryl monomers to yield a polyether. Exemplary dihaloaryl monomers include 1 ,6-dichlorobenzene, 4,4'-dichlorobiphenyl, 4,4'- dichlorodiphenylsulfide, 1,6-difluorobenzene, 4,4'-difluorobiphenyl, 4,4'- difluorodiphenylsulfie, and combinations thereof. For example, the monomer of formula I may be copolymerized with decafluorobiphenyl in N-methyl-2-pyrollidone (NMP), in the presence of a base such as potassium carbonate, at the temperature between about 100 and about 25O ⁰ C

[0022] In another embodiment, the monomer of formula I may be copolymerized with dihalobenzophenone monomer to yield a polyetherketone. Other dihalobenzophenone monomers include l,4-bis(4'-chlorobenzoyl)benzene, l,4-bis(4'- fluorobenzoyl)benzene, 1 -(4 ' -chlorobenzoyl-4-(4 ' ' -fluorobenzoyl)benzene, and combinations thereof. For example, the monomer of formula I together with the disodium salt of bisphenol A may be reacted with 4,4'-dichlorobenzophenone in orthodichlorobenzene at a temperature between about 100 and about 25O ⁰ C in the presence of a phase transfer catalyst such as hexaethyl guanidinium chloride.

[0023] In another embodiment, the monomer of formula I may be copolymerized with a bis(halophthalimide) such as bis(4-chlorophthalimide) to obtain a polyetherimide. Other bis(halophthalimide)s include l,3-bis[N-(4-fluorophthalimido)]benzene, 1,4- bis[N-(4-fluorophthalimido)]benzene, l,3-bis[N-(3-fluorophthalimido)] benzene, 1,4- bis[N-(3-fluorophthalimido)] benzene, 4,4'-bis[N-(4-fluorophthalimido)]phenyl ether, 4,4'-bis[N-(3-fluorophthalimido)]phenyl ether, 4,4'-bis[N-(4- chlorophthalimido)]phenyl ether, 4,4'-bis[N-(3-chlorophthalimido)]phenyl ether, 1,3- bis[N-(4-chlorophthalimido)]benzene, 1 ,4-bis[N-(4-chlorophthalimido)]benzene, 1,3- bis[N-(3-chlorophthalimido)]benzene, 1 ,4-bis[N-(3-chlorophthalimido)]benzene, 1 - [N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, l-[N-(4- chlorophthalimido)]-4-[N-(3-chlorophthalimido)benzene, and combinations thereof.

[0024] Reaction conditions useful for the preparation of the polymer compositions provided by the present invention include the use of polar solvents and bases of suitable strength. Exemplary solvents include chloroform, methylene chloride,

orthodichlorobenzene, veratrole, anisole, and the like, and combinations thereof. Exemplary bases include triethylamine, sodium hydroxide, potassium hydroxide, and the like, and combinations thereof. Suitable catalysts may also be employed to effect the polymerization reaction.

[0025] In certain embodiments, the polymerization reaction may be conducted at a suitable temperature that ranges from about room temperature to about the boiling point of the solvent of choice. The polymerization may also be conducted at atmospheric pressure, subatmospheric pressures, or superatmospheric pressures. The polymerization reaction is conducted for a time period necessary to achieve polymer of a suitable molecular weight. The molecular weight of a polymer is determined by any of the techniques known to those skilled in the art, and include viscosity measurements, light scattering, osmometry, and the like. The molecular weight of a polymer is typically represented as a number average molecular weight M _n , or weight average molecular weight, M _w . A particularly useful technique to determine molecular weight averages is gel permeation chromatography (GPC), from wherein both number average and weight average molecular weights are obtained. In some embodiments, polymers of M _w greater than 30,000 grams per mole (g/mol) is desirable, in other embodiments, polymers of M _w greater than 50,000 g/mol is desirable, while in yet other embodiments, polymer of M _w greater than 80,000 g/mol is desirable.

[0026] The polymerization reaction may be controlled the addition of a suitable monofunctional reactant, sometimes also referred to in the art as "end-capping agents", or "chain stoppers". The chain stopper serves to limit polymer molecular weight. Suitable phenolic chain stoppers include phenol, p-cumylphenol, and the like. Suitable aromatic halide chain stoppers include, 4-chlorophenyl phenyl sulfone, 4- fluorophenyl phenyl sulfone, 4-chlorophenyl phenyl ketone, and the like.

[0027] Polymers provided in the present invention may find use in a wide variety of applications that include, but are not limited to, light emitting electrochemical cells, photo detectors, photo conductive cells, photo switches, display devices and the like. Thus, in one aspect, the invention provides a light emitting comprising at least one

electrode, at least one hole injection layer, at least one light emissive layer; wherein the light emissive layer comprises a polymer comprising structural units of formula II.

[0028] The polymer compositions of the present invention are particularly well suited for use in an electroactive layers in organic light emitting devices. In one embodiment, the present invention provides an organic light emitting device comprising an electroactive layer which consists essentially of the polymer compositions. In another embodiment, the present invention provides an organic light emitting device comprising the polymer compositions as a constituent of an electroactive layer of an organic light emitting device. In one embodiment, the present invention provides an organic light emitting device comprising the polymer compositions as a constituent of a light emitting electroactive layer of an organic light emitting device.

[0029] An organic light emitting device typically comprises multiple layers which include in the simplest case, an anode layer and a corresponding cathode layer with an organic electroluminescent layer disposed between said anode and said cathode. When a voltage bias is applied across the electrodes, electrons are injected by the cathode into the electroluminescent layer while electrons are removed from (or "holes" are "injected" into) the electroluminescent layer from the anode. Light emission occurs as holes combine with electrons within the electroluminescent layer to form singlet or triplet excitons, light emission occurring as singlet excitons transfer energy to the environment by radiative decay.

[0030] Other components which may be present in an organic light emitting device I addition to the anode, cathode, and light emitting material include hole injection layers, electron injection layers, and electron transport laers. The electron transport layer need not be in contact with the cathode, and frequently the electron transport layer is not an efficient hole transporter and thus it serves to block holes migrating toward the cathode. During operation of an organic light emitting device comprising an electron transport layer, the majority of charge carriers (i.e. holes and electrons) present in the electron transport layer are electrons and light emission can occur through recombination of holes and electrons present in the electron transport layer.

Additional components which may be present in an organic light emitting device include hole transport layers, hole transporting emission (emitting) layers and electron transporting emission (emitting) layers.

[0031] Compounds of formula I have triplet energy states that are useful in applications such as organic light emitting devices (OLEDs), as they may give rise to highly efficient devices. Further, the triplet energy of these compounds may be high enough that it may be greater than those of guest dyes used in devices, and thus may serve as host molecules. The compounds of the present invention are particularly well suited for use in hole transport layers in organic light emitting devices. In one embodiment, the present invention relates to an organic light emitting device comprising the compounds as a constituent of a hole transport layer of an organic light emitting device.

[0032] The organic electroluminescent layer is a layer within an organic light emitting device which when in operation contains a significant concentration of both electrons and holes and provides sites for exciton formation and light emission. A hole injection layer is a layer in contact with the anode which promotes the injection of holes from the anode into the interior layers of the OLED; and an electron injection layer is a layer in contact with the cathode that promotes the injection of electrons from the cathode into the OLED; an electron transport layer is a layer which facilitates conduction of electrons from cathode to a charge recombination site. The electron transport layer need not be in contact with the cathode, and frequently the electron transport layer is not an efficient hole transporter and thus it serves to block holes migrating toward the cathode. During operation of an organic light emitting device comprising an electron transport layer, the majority of charge carriers (i.e. holes and electrons) present in the electron transport layer are electrons and light emission can occur through recombination of holes and electrons present in the electron transport layer. A hole transport layer is a layer which when the OLED is in operation facilitates conduction of holes from the anode to charge recombination sites and which need not be in contact with the anode. A hole transporting emission layer is a layer in which when the OLED is in operation facilitates the conduction of holes to charge recombination sites, and in which the majority of charge carriers are holes,

and in which emission occurs not only through recombination with residual electrons, but also through the transfer of energy from a charge recombination zone elsewhere in the device. An electron transporting emission layer is a layer in which when the OLED is in operation facilitates the conduction of electrons to charge recombination sites, and in which the majority of charge carriers are electrons, and in which emission occurs not only through recombination with residual holes, but also through the transfer of energy from a charge recombination zone elsewhere in the device.

[0033] Materials suitable for use as the anode include materials having a bulk conductivity of at least about 100 ohms per square, as measured by a four-point probe technique. Indium tin oxide (ITO) is frequently used as the anode because it is substantially transparent to light transmission and thus facilitates the escape of light emitted from electro-active organic layer. Other materials which may be utilized as the anode layer include tin oxide, indium oxide, zinc oxide, indium zinc oxide, zinc indium tin oxide, antimony oxide, and mixtures thereof.

[0034] Materials suitable for use as the cathode include by zero valent metals which can inject negative charge carriers (electrons) into the inner layer(s) of the OLED. Various zero valent metals suitable for use as the cathode 20 include K, Li, Na, Cs, Mg, Ca, Sr, Ba, Al, Ag, Au, In, Sn, Zn, Zr, Sc, Y, elements of the lanthanide series, alloys thereof, and mixtures thereof. Suitable alloy materials for use as the cathode layer include Ag-Mg, Al-Li, In-Mg, Al-Ca, and Al-Au alloys. Layered non-alloy structures may also be employed in the cathode, such as a thin layer of a metal such as calcium, or a metal fluoride, such as LiF, covered by a thicker layer of a zero valent metal, such as aluminum or silver. In particular, the cathode may be composed of a single zero valent metal, and especially of aluminum metal.

[0035] Light emitting devices according to the present invention include polymers having formula II in the hole injection layer. The polymers may be used in place of, or in addition to traditional materials such as poly(3,4-ethylenedioxythiophene), which is commercially available from H. C. Stark, Inc. under the BAYTRON® tradename, and polymers based on the thieno[3,4b]thiophene (TT) monomer,

commercially available from Air Products Corporation. In particular, the polymers may be blended with PEDOT to form a hole injection layer.

[0036] Materials suitable for use in hole transporting layers include l,l-bis((di-4- tolylamino) phenyl)cyclohexane, N ₅ N'- bis(4-methylphenyl)-N,N'-bis(4-ethylphenyl)- (l,r-(3,3'-dimethyl)biphenyl)-4,4'-diamine, tetrakis-(3-methylphenyl)-N,N,N',N'-2,5- phenylenediamine, phenyl-4-N,N-diphenylaminostyrene, p-(diethylamino) benzaldehyde diphenylhydrazone, triphenylamine, l-phenyl-3-(p- (diethylamino)styryl)-5 -(p-(diethylamino)phenyl)pyrazoline, 1 ,2-trans-bis(9H- carbazol-9-yl)cyclobutane, N,N,N',N'-tetrakis(4-methylphenyl)-( 1 , 1 '-biphenyl)-4,4'- diamine, copper phthalocyanine, polyvinylcarbazole, (phenylmethyl)polysilane; poly(3,4- ethylendioxythiophene) (PEDOT), polyaniline, polyvinylcarbazole, triaryldiamine, tetraphenyldiamine, aromatic tertiary amines, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group, and polythiophenes as disclosed in U.S. Pat. No. 6,023,371.

[0037] Materials suitable for use as the electron transport layer include poly(9,9- dioctyl fluorene), tris(8-hydroxyquinolato) aluminum (AIq ₃ ), 2,9-dimethyl-4,7- diphenyl- 1 , 1 -phenanthroline, 4,7-diphenyl- 1 , 10-phenanthroline, 2-(4-biphenylyl)-5- (4-t-butylphenyl)-l,3,4-oxadiazole, 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)- 1,2,4- triazole, 1,3,4-oxadiazole-containing polymers, 1,3,4-triazole-containing polymers, quinoxaline-containing polymers, and cyano-PPV.

[0038] Materials suitable for use in the light emitting layer include electroluminescent polymers such as poly(9,9-dioctyl fluorene) and copolymers thereof, such as F8-TFB.

[0039] In one aspect, polymers comprising structural units of formula II may form part of the hole collection layer, while in another aspect, polymers comprising structural units of formula II form part of the hole injection layer. Thus, in one aspect, the present invention relates to more efficient organic light emitting devices comprising polymers comprising structural units of formula II.

DEFINITIONS

[0040] As used herein, the term "aromatic radical" refers to an array of atoms having a valence of at least one comprising at least one aromatic group. The array of atoms having a valence of at least one comprising at least one aromatic group may include heteroatoms such as nitrogen, sulfur, selenium, silicon and oxygen, or may be composed exclusively of carbon and hydrogen. As used herein, the term "aromatic radical" includes but is not limited to phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl radicals. As noted, the aromatic radical contains at least one aromatic group. The aromatic group is invariably a cyclic structure having 4n+2 "delocalized" electrons where "n" is an integer equal to 1 or greater, as illustrated by phenyl groups (n = 1), thienyl groups (n = 1), furanyl groups (n = 1), naphthyl groups (n = 2), azulenyl groups (n = 2), anthraceneyl groups (n = 3) and the like. The aromatic radical may also include nonaromatic components. For example, a benzyl group is an aromatic radical which comprises a phenyl ring (the aromatic group) and a methylene group (the nonaromatic component). Similarly a tetrahydronaphthyl radical is an aromatic radical comprising an aromatic group (C ₆ Hs) fused to a nonaromatic component -(CH ₂ V. For convenience, the term "aromatic radical" is defined herein to encompass a wide range of functional groups such as alkyl groups, alkenyl groups, alkynyl groups, haloalkyl groups, haloaromatic groups, conjugated dienyl groups, alcohol groups, ether groups, aldehydes groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups, nitro groups, and the like. For example, the 4-methylphenyl radical is a C ₇ aromatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 2-nitrophenyl group is a C ₆ aromatic radical comprising a nitro group, the nitro group being a functional group. Aromatic radicals include halogenated aromatic radicals such as A- trifluoromethylphenyl, hexafluoroisopropylidenebis(4-phen-l-yloxy) (i.e., - OPhC(CF ₃ ) ₂ PhO-), 4-chloromethylphen-l-yl, 3-trifluorovinyl-2-thienyl, 3- trichloromethylphen-1-yl (i.e., 3-CCIsPh-), 4-(3-bromoprop-l-yl)phen-l-yl (i.e., A- BrCH ₂ CH ₂ CH ₂ Ph-), and the like. Further examples of aromatic radicals include A- allyloxyphen-1-oxy, 4-aminophen-l-yl (i.e., 4-H ₂ NPh-), 3-aminocarbonylphen-l-yl (i.e., NH ₂ COPh-), 4-benzoylphen-l-yl, dicyanomethylidenebis(4-phen-l-yloxy) (i.e., -OPhC(CN) ₂ PhO-), 3-methylphen-l-yl, methylenebis(4-phen-l-yloxy) (i.e., -

OPhCH ₂ PhO-), 2-ethylphen-l-yl, phenylethenyl, 3-formyl-2-thienyl, 2-hexyl-5- furanyl, hexamethylene-l,6-bis(4-phen-l-yloxy) (i.e., -OPh(CH ₂ ) ₆ PhO-), A- hydroxymethylphen-1-yl (i.e., 4-HOCH ₂ Ph-), 4-mercaptomethylphen-l-yl (i.e., A- HSCH ₂ Ph-), 4-methylthiophen-l-yl (i.e., 4-CH ₃ SPh-), 3-methoxyphen-l-yl, 2- methoxycarbonylphen-1-yloxy (e.g. methyl salicyl), 2-nitromethylphen-l-yl (i.e., 2- NO ₂ CH ₂ Ph), 3-trimethylsilylphen-l-yl, 4-t-butyldimethylsilylphenl-l-yl, 4-vinylphen- 1-yl, vinylidenebis(phenyl), and the like. The term "a C ₃ - C ₁₀ aromatic radical" includes aromatic radicals containing at least three but no more than 10 carbon atoms. The aromatic radical 1-imidazolyl (C ₃ H ₂ N ₂ -) represents a C ₃ aromatic radical. The benzyl radical (C ₇ H ₇ -) represents a C ₇ aromatic radical.

[0041] As used herein the term "cycloaliphatic radical" refers to a radical having a valence of at least one, and comprising an array of atoms which is cyclic but which is not aromatic. As defined herein a "cycloaliphatic radical" does not contain an aromatic group. A "cycloaliphatic radical" may comprise one or more noncyclic components. For example, a cyclohexylmethyl group (CeHnCH ₂ -) is an cycloaliphatic radical which comprises a cyclohexyl ring (the array of atoms which is cyclic but which is not aromatic) and a methylene group (the noncyclic component). The cycloaliphatic radical may include heteroatoms such as nitrogen, sulfur, selenium, silicon and oxygen, or may be composed exclusively of carbon and hydrogen. For convenience, the term "cycloaliphatic radical" is defined herein to encompass a wide range of functional groups such as alkyl groups, alkenyl groups, alkynyl groups, haloalkyl groups, conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups, nitro groups, and the like. For example, the 4-methylcyclopent-l-yl radical is a C ₆ cycloaliphatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 2-nitrocyclobut-l-yl radical is a C ₄ cycloaliphatic radical comprising a nitro group, the nitro group being a functional group. A cycloaliphatic radical may comprise one or more halogen atoms which may be the same or different. Halogen atoms include, for example; fluorine, chlorine, bromine, and iodine. Cycloaliphatic radicals comprising one or more halogen atoms

include 2-trifluoromethylcyclohex-l-yl, 4-bromodifluoromethylcyclooct-l-yl, 2- chlorodifluoromethylcyclohex- 1 -yl, hexafluoroisopropylidene-2,2-bis (cyclohex-4-yl) (i.e., -C ₆ HIOC(CFS) ₂ C ₆ HIO-), 2-chloromethylcyclohex-l-yl, 3- difluoromethylenecyclohex- 1 -yl, 4-trichloromethylcyclohex- 1 -yloxy , A- bromodichloromethylcyclohex- 1 -ylthio, 2-bromoethylcyclopent- 1 -yl, 2- bromopropylcyclohex-1 -yloxy (e.g. CHsCHBrCH ₂ C ₆ HiOO-), and the like. Further examples of cycloaliphatic radicals include 4-allyloxycyclohex-l-yl, A- aminocyclohex-1-yl (i.e., H ₂ NC ₆ Hi ₀ -), 4-aminocarbonylcyclopent-l-yl (i.e., NH ₂ COCsH ₈ -), 4-acetyloxycyclohex- 1 -yl, 2,2-dicyanoisopropylidenebis(cyclohex-4- yloxy) (i.e., -OC ₆ H _IO C(CN) ₂ C ₆ H _IO O-), 3-methylcyclohex-l-yl, methylenebis(cyclohex-4-yloxy) (i.e., -OC ₆ H _IO CH ₂ C ₆ H _IO O-), 1-ethylcyclobut-l-yl, cyclopropylethenyl, 3 -formyl-2-terahydrofuranyl, 2-hexyl-5 -tetrahydrofuranyl, hexamethylene-l,6-bis(cyclohex-4-yloxy) (i.e., -O C ₆ Hio(CH ₂ ) ₆ C ₆ HioO-), A- hydroxymethylcyclohex-1-yl (i.e., 4-HOCH ₂ C ₆ HiO-), 4-mercaptomethylcyclohex-l-yl (i.e., 4-HSCH ₂ C ₆ HiO-), 4-methylthiocyclohex-l-yl (i.e., 4-CH ₃ SC ₆ HiO-), A- methoxycyclohex-1-yl, 2-methoxycarbonylcyclohex-l -yloxy (2-CH3θCOC ₆ HioO-), 4-nitromethylcyclohex-l-yl (i.e., NO ₂ CH ₂ C ₆ Hi ₀ -), 3-trimethylsilylcyclohex-l-yl, 2-t- butyldimethylsilylcyclopent- 1 -yl, 4-trimethoxysilylethylcyclohex- 1 -yl (e.g. (CH ₃ 0)3SiCH ₂ CH ₂ C ₆ Hio-), 4-vinylcyclohexen-l-yl, vinylidenebis(cyclohexyl), and the like. The term "a C ₃ - Cio cycloaliphatic radical" includes cycloaliphatic radicals containing at least three but no more than 10 carbon atoms. The cycloaliphatic radical 2-tetrahydrofuranyl (C4H7O-) represents a C ₄ cycloaliphatic radical. The cyclohexylmethyl radical (C ₆ Hi ₁ CH ₂ -) represents a C ₇ cycloaliphatic radical.

[0042] As used herein the term "aliphatic radical" refers to an organic radical having a valence of at least one consisting of a linear or branched array of atoms which is not cyclic. Aliphatic radicals are defined to comprise at least one carbon atom. The array of atoms comprising the aliphatic radical may include heteroatoms such as nitrogen, sulfur, silicon, selenium and oxygen or may be composed exclusively of carbon and hydrogen. For convenience, the term "aliphatic radical" is defined herein to encompass, as part of the "linear or branched array of atoms which is not cyclic" organic radicals substituted with a wide range of functional groups such as alkyl

groups, alkenyl groups, alkynyl groups, haloalkyl groups , conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups, nitro groups, and the like. For example, the 4-methylpent-l-yl radical is a Ce aliphatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 4-nitrobut-l-yl group is a C ₄ aliphatic radical comprising a nitro group, the nitro group being a functional group. An aliphatic radical may be a haloalkyl group which comprises one or more halogen atoms which may be the same or different. Halogen atoms include, for example; fluorine, chlorine, bromine, and iodine. Aliphatic radicals comprising one or more halogen atoms include the alkyl halides trifluoromethyl, bromodifluoromethyl, chlorodifluoromethyl, hexafluoroisopropylidene, chloromethyl, difluorovinylidene, trichloromethyl, bromodichloromethyl, bromoethyl, 2-bromotrimethylene (e.g. - CH ₂ CHBrCH ₂ -), and the like. Further examples of aliphatic radicals include allyl, aminocarbonyl (i.e., -CONH ₂ ), carbonyl, 2,2-dicyanoisopropylidene (i.e., - CH ₂ C(CN) ₂ CH ₂ -), methyl (i.e., -CH ₃ ), methylene (i.e., -CH ₂ -), ethyl, ethylene, formyl (i.e. -CHO), hexyl, hexamethylene, hydroxymethyl (i.e. -CH ₂ OH), mercaptomethyl (i.e., -CH ₂ SH), methylthio (i.e., -SCH ₃ ), methylthiomethyl (i.e., -CH ₂ SCH ₃ ), methoxy, methoxycarbonyl (i.e., CH ₃ OCO-) , nitromethyl (i.e., -CH ₂ NO ₂ ), thiocarbonyl, trimethylsilyl ( i.e.(CH ₃ ) ₃ Si-), t-butyldimethylsilyl, 3- trimethyoxysilypropyl (i.e., (CH ₃ O) ₃ SiCH ₂ CH ₂ CH ₂ -), vinyl, vinylidene, and the like. By way of further example, a Ci - C ₁₀ aliphatic radical contains at least one but no more than 10 carbon atoms. A methyl group (i.e., CH ₃ -) is an example of a Ci aliphatic radical. A decyl group (i.e., CH ₃ (CH2)g-) is an example of a C ₁₀ aliphatic radical.

[0043] Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22

to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

EXAMPLES

Chemicals and reagents

[0044] Chemicals and reagents are obtained from Aldrich. Flash chromatography was carried out by Fisher Scientific (100-200 mesh) or Aldrich (60-350 mesh) silica gel, prepacked silical gel coumn by Isco. Thin layer chromatography was carried out on commercially available pre-coated glass plates (Analtech, GF, 250 microns).

General methods

[0045] Molecular weights were determined relative to polystyrene standards on a Perkin Elmer Series 200 GPC equipped with a Polymer Laboratories size exclusion column (PLgel 5μm MIXED-C, 300x7.5 mm kept at 40 ⁰ C) using chloroform with 3.6 % v/v isopropanol as the mobile phase. NMR spectra were measured on a Bruker 400 or Bruker Advance 500 spectrometers.

Synthesis

[0046] The synthesis of the N-(l,3-resorcinol)carbazole and N-hydroquinone carbazole was done in a two-step process as shown in scheme 1, addition of bromo- dimethoxy benzene to carbazole followed by deprotecting the methoxy group to give rise to the dihydroxy compound. N-Arylation can be achieved by Pd catalyzed procedures or use CuI as the catalyst. Condensation polymerization were synthesized by typical procedures.

Scheme 1

EXAMPLE 1 : Synthesis of Compound 1 9-(3,5-dimethoxyphenyl)-carbazole

[0047] To a three neck round bottom flask, was charged bromo-3,5- dimethoxybenzene (1.54 g, 7.1 mmol), carbazole (1.186 g, 7.1 mmol), potassium phosphate (3 g, 14.2 mmol) and copper iodide (0.14 g, 0.7 mmol). Dioxane (40 ml) was added and the reaction flask. The flask was evacuated and flushed with argon. Dimethylethylene diamine (0.14 g, 1.6 mmol) was then added to the reaction flask under a strong purge of argon. The reaction mixture was then heated at 95 ⁰ C for 48 h under argon. The reaction was followed by TLC. After the reaction was complete, the solution was cooled down to room temperature, and 10 mL Of H ₂ O was added. The reaction mixture was extracted with methylene chloride and the organic and aqueous phases were separated. The organic phase was further washed twice with 100 mL of water (x2) and once with 100 mL of brine (xl) and dried over Na ₂ SO ₄ . After solvent removal under vacuo, afforded crude product. Crude product was dissolved in CH ₂ Cl ₂ and hexanes were added until the colored residues precipitated out. The solution was filtered to remove the colored residues. The mother liquor was concentrated to afford 1.Og (46.5%) of light yellow oil as the product. ¹ H NMR (CDCl ₃ ) δ 7.98 (d, 2H), 7.35 (d, 2H), 7.23 (d, 2H), 7.11 (t, 2H), 6.6 (s, 2H), 6.43 (s, IH), 3.65 (s, 6H). EI-MS: 303(M+).

EXAMPLE 2: Synthesis of Compound 2 9-(3,5-hydroxyphenyl)-carbazole

[0048] In a 500 niL round bottom flask equipped with a stir bar, 31.3 g of compound 1 (103 mmol) was added to a 200 mL of anhydrous CH ₂ Cl ₂ . Solution was cooled in a dry ice-acetone bath. Boron tribromide (180 mmol, 180 mL of IM solution in CH ₂ Cl ₂ ) was added via syringe drop wise to the solution. The flask was further chilled in the dry ice bath and allowed to equilibrate to room temperature overnight. After the reaction was complete, the solution was decanted into 100 mL of ice water while stirring. After 30 minutes of hydrolysis, the organic layer was extracted twice with 200 mL of CH ₂ Cl ₂ . The organic layer was then washed twice with 200 mL of cold water to neutralize any excess BBr ₃ . Solution was dried with sodium sulfate and the solvent was evaporated using a rotary evaporator to give the crude product. Recrystallization from THF/hexanes afforded 12.74 g (44.98%)of product that was then subsequently used for polymerization reactions. ¹ H NMR (CDCl ₃ ) δ 8.15 (d, 2H), 7.52 (d, 2H), 7. 44 (t, 2H), 7.32 (t, 2H), 6.66 (s, 2H), 6.47 (s, IH).

EXAMPLE 3: Synthesis of Compound 3 9-(2,5-dimethoxyphenyl)-carbazole

[0049] The procedure described in Example 1 was followed here using the bromo- 2,5-dimethoxybenzene as one of the reactants.

EXAMPLE 4: Synthesis of Compound 3 9-(2,5-hydroxyphenyl)-carbazole (Compound 3)

[0050] The procedure described in Example 2 was followed using compound 3 as the starting material.

EXAMPLE 5: Polymerization of Compound 2 with Terephthaloyl dichloride.

[0051] 0.3969 g (1.441 mmol) of compound 2 and 0.2956g (1.456 mmol) of 1,4- terephthaloyl dichloride and 4mL of anhydrous CHCl ₃ was charged into a dry round bottom flask with a magnetic stirring bar under nitrogen atmosphere. The resulting milky solution was immersed in an ice-salt bath for 15 min and then 0.533 mL of dry triethylamine was added using a syringe. Solution became clear immediately. The mixture was maintained at 0-5 ⁰ C with stirring for 1 h, allowed to warm to room

temperature, and stirred for additional hour. Then, 0.0032g of cumylphenol was added. Then the mixture was diluted with 5 mL of CH ₂ Cl ₂ , and was washed successively twice with equal volumes of 1 N HCl and water. The solution was precipitated into 40 mL of methanol. The collected polymer was redissolved in 10 mL of CH ₂ Cl ₂ and this solution was added slowly to 100 mL of boiling, deionized water. The solids were again collected, air-dried, redissolved in fresh CH ₂ Cl ₂ (4 mL) and reprecipitated into methanol. The resulting polymer (0.3747g) was dried at 80 ⁰ C in a vacuum oven overnight. GPC analysis indicated that the polymer has weight average molecular weight Mw of 4241, and a polydispersity index PDI of 1.61.

EXAMPLE 6: Polymerization of Compound 2 with Bisphenol A bischloro formate.

[0052] A dry reaction vessel equipped with a magnetic stirring bar under nitrogen atmosphere, was charged with the compound 2 (0.275Og, 1 mmol), BPA- bischloroformate (0.353 g, 1 mmol), and 4 mL of dry CH ₂ Cl ₂ . The resulting milky solution was immersed in an ice-salt bath for 15 min and then charged with 0.37 mL of dry triethylamine. Solution immediately became clear. The mixture was maintained at 0-5 ⁰ C with stirring for 1 h, allowed to warm to room temperature, and stirred overnight. Then the mixture was diluted with 10 mL of CH ₂ Cl ₂ , 15 mL of 10% NaHCO3 was added, and the mixture was stirred for 10 min and then transferred to a separatory funnel. The aqueous phase was discarded and the organic phase was washed successively with equal volumes of 1 N HCl once and water twice. Then solution was precipitated into 40 mL of methanol. The collected polymer was redissolved in 10 mL of CH ₂ Cl ₂ and this solution was added slowly to 1000 mL of boiling, deionized water. The solids were again collected, air-dried, redissolved in fresh CH ₂ Cl ₂ (12 mL) and reprecipitated again into methanol. The resulting polymer (0.26g) was dried at 80 ⁰ C in a vacuum oven overnight. GPC analysis indicated that the polymer has weight average molecular weight Mw of 7362, and a polydispersity index PDI of 1.68.

EXAMPLE 7: Polymerization of Compound 2 with difluorodiphenylsulfone

[0053] 0.5506 g (20 mmol) of compound 2 and 0.4146 g OfK ₂ CO ₃ were placed 5OmL of three neck round bottom flask was charged with 7mL of DMAc and 4mL of toluene. The reaction flask was equipped with an overhead stirrer and a Dean-stark trap. Reaction mixture was heated to 130 ⁰ C to remove toluene. After all toluene was removed, difluorodiphenylsulfone (0.5085 g, 20 mmol) was added along with 4mL of toluene. Toluene distillation continued. After all the toluene was removed, reaction temperature was increased to 150 ⁰ C. After 4 hours, reaction was stopped and the reaction mixture was precipitated into methanol (1 :10 v/v ratio). The powder was collected and redissolved in 10 mL of CHCl ₃ and precipitated into methanol. Collected 110 mg of powder. GPC analysis indicated that the polymer has weight average molecular weight Mw of 4103, and a polydispersity index PDI of 1.26.

General procedure for life time decay measurements

[0054] The lifetime of triplet excited states were measured using an Edinburgh CD920 spectrometer equipped with a cooled R928 photo multiplier tube. The typical procedure was to place a sample in a vacuum dewer and then pump down to 4* 1OE ^"5 torr. Then the sample was optically excited at 394nm with a pulsed diode laser (class HIB, 390-420nm, maximum power of 5mW). Time resolved emission spectra were measured at 470nm. Polystyrene (PS) used in this work was GPC standard Mw=I 8,700 obtained from Aldrich and used as received. Poly(9-vinylcarbazole) (PVK), Mw- 1,100,000, was obtained from Aldrich. Iridium (III) bis(2-(4,6- difluorephenyl)pyridinato-N, C ² ) (FIrpic) was obtained from American Dye Sources, Inc. Quebec, Canada.

Sample preparation: Samples for this experiment were prepared in the following manner:

EXAMPLE 8

[0055] A mixture of lwt% FIrpic in PS was prepared by mixing 0.020ml of 0.5wt% FIrpic (lOmg of FIrpic in 2ml THF) with 1.0ml of lwt% PS in THF. A thin film sample [PS:FIrpic] was obtained by spin-coating the solution onto a pre-cleaned quartz substrate.

EXAMPLE 9

[0056] A mixture of lwt% FIrpic in polymer from Example 6 was prepared by mixing 0.020ml of 0.5wt% FIrpic (lOmg of FIrpic in 1ml THF) with 1.0ml of lwt% 62-90 (lOmg of 62-90 in 1ml THF). A thin film sample was obtained by spin-coating the solution onto a pre-cleaned quartz substrate.

COMPARATIVE EXAMPLE 1

[0057] A mixture of lwt% FIrpic in Poly(N-vinyl carbazole) was prepared by mixing 0.020ml of 0.5wt% (lOmg of Firpic in 1ml THF) with 1.0ml of lwt% PVK in THF. A thin film sample was obtained by spin-coating the solution onto a pre-cleaned quartz substrate.

[0058] Figure 1 shows the time resolved photoluminescence spectra of the device comprising the copolycarbonate from Example 6, and that of the device comprising polystyrene. The phosphorescent dye FIrpic had comparable triplet decay profiles (or equivalently decay lifetimes) when dispersed in the copolycarbonate of Example 6 (dotted line) relative to the insulating polystyrene (solid line), indicating that there is no energy back transfer from the dye FIrpic to the polymer host. Thus, polymer of the invention is suitable as a host material for FIrpic in blue phosphorescent OLEDs. Figure 2 shows the time resolved photoluminescence spectra of device comprising poly(N-vinyl carbazole) and that od the device comprising polystyrene. The spectra from the device comprising poly(N-vinyl carbazole) (dotted line) exhibited a much faster decay profile than the device comprising polystyrene (solid line), indicating that there is energy back transfer from FIrpic to poly(N-vinyl carbazole).