Mono-, Oligo- and Polythieno(2,3-b)thiophenes

Field of Invention

0001The invention relates to novel mono-, oligo- and polythieno[2,3-b]thiophenes. The invention further relates to their use as semiconductors or charge transport materials, in optical, electrooptical or electronic devices like for example liquid crystal displays, optical films, organic field effect transistors (FET or OFET) for thin film transistor liquid crystal displays and integrated circuit devices such as RFID tags, electroluminescent devices in flat panel displays, and in photovoltaic and sensor devices. The invention further relates to a field effect transistor, light emitting device or ID tag comprising the novel polymers.

Background and Prior Art

0002Organic materials have recently shown promise as the active layer in organic based thin film transistors and organic field effect transistors [see H. E. Katz, Z. Bao and S. L. Gilat, <i>Acc. Chem. Res</i>., 2001, <b>34,</b> 5, 359]. Such devices have potential applications in smart cards, security tags and the switching element in flat panel displays. Organic materials are envisaged to have substantial cost advantages over their silicon analogues if they can be deposited from solution, as this enables a fast, large-area fabrication route.

0003The performance of the device is principally based upon the charge carrier mobility of the semi-conducting material and the current on/off ratio, so the ideal semiconductor should have a low conductivity in the off state, combined with a high charge carrier mobility (> 1 x 10^-3 cm²V^-1 s^-1). In addition, it is important that the semi-conducting material is relatively stable to oxidation i.e. it has a high ionisation potential, as oxidation leads to reduced device performance.

0004Regioregular head-to-tail poly(3-hexylthiophene) has been reported with charge carrier mobility between 1 x 10^-5 and 4.5 x 10^-2 cm² V^-1 s^-¹, but with a rather low current on/off ratio between 10 and 10³ [see Z. Bao et al., <i>Appl. Pys. Lett.,</i> 1996, <b>69</b>, 4108]. This low on/off current is due in part to the low ionisation potential of the polymer, which can lead to oxygen doping of the polymer under ambient conditions, and a subsequent high off current [see H. Sirringhaus et al., <i>Adv. Solid State Phys.,</i> 1999, <b>39,</b> 101].

0005A high regioregularity leads to improved packing and optimised microstructure, leading to improved charge carrier mobility [see <nplcit id="ncit0001" npl-type="s"><text>H. Sirringhaus et al., Science, 1998, 280, 1741-1744</text></nplcit>; <nplcit id="ncit0002" npl-type="s"><text>H. Sirringhaus et al., Nature, 1999, 401, 685-688</text></nplcit>; and <nplcit id="ncit0003" npl-type="s"><text>H. Sirringhaus, et al., Synthetic Metals, 2000, 111-112, 129-132</text></nplcit>]. In general, poly(3-alkylthiophenes) show improved solubility and are able to be solution processed to fabricate large area films. However, poly(3-alkylthiophenes) have relatively low ionisation potentials and are susceptible to doping in air.

0006It is an aim of the present invention to provide new materials for use as semiconductors or charge transport materials, which are easy to synthesize, have high charge mobility, good processibility and oxidative stability.

0007Another aim of the invention is to provide new semiconductor and charge transport components, and new and improved electrooptical, electronic and electroluminescent devices comprising these components, like field effect transistors (FET) as components of integrated circuitry or of thin film transistors (TFT), and organic light emitting diode (OLED) applications like electroluminescent displays or backlights of liquid crystal displays.

0008Other aims of the invention are immediately evident to those skilled in the art from the following description.

0009The inventors have found that these aims can be achieved by providing mono-, oligo- and (co)polymers of thieno[2,3-b]thiophene as semiconductors and charge transport materials.

0010The inventors of this invention have found that incorporation of thieno[2,3-b]thiophene <b>(1)</b> units into conjugated polymers yields materials which are useful for charge transport in FET's, and for electroluminescence in OLED's. The incorporation of this core has the effect of lowering the ionisation potential of the resulting polymers, resulting in improved air stability and reduced transistor off currents. It is believed that this effect is due to the fact that quinoidal type resonance structures cannot be formed for thieno[2,3-b]thiophene as shown in Diagram 1, which therefore limits the effective conjugation length of the polymer backbone, since charge cannot delocalise through this unit. This is in contrast for the other regioisomer, thieno[3,2-b]thiophene (<b>2</b>), or 2,2-bithiophene (<b>3</b>), in which fully delocalised quinoidal-type structures can be realised, as shown in Diagram 1.

0011<u style="single">Diagram 1:</u> Charge delocalisation though dithiophene units, where A represents a conjugated species such as a thiophene or benzene ring. <chemistry id="chem0001" num="0001"><img file="EP1510535B1_D0001.tif" /></chemistry>

0012Therefore once an exciton or hole is formed in the polymer, it cannot fully delocalise along the polymer backbone, as depicted in Diagram 2. This limits the effective conjugation to only the aromatic units between any two thieno[2,3-b]thiophenes (in Diagram 2, effectively 2 thiophene units plus 2 thieno[2,3-b]thiophene units). This provides a ready means to tune the effective conjugation length in a conjugated polymer. This is desirable because shorter conjugation lengths result in lower HOMO energy levels (since there are less degenerate states) and therefore improved oxidative stability. Since the dominant mechanism for charge transport in conjugated polymers is via a hole-hopping mechanism, the polymers are still able to exhibit good mobilities providing close packed morphology is obtained.

0013<u style="single">Diagram 2:</u> Effective conjugation in a co-polymer containing thieno[2,3-b]thiophene. <chemistry id="chem0002" num="0002"><img file="EP1510535B1_D0002.tif" /></chemistry>

0014In electroluminescent applications this provides a ready means to colour tune the polymers, and also results in improved colour purity since each polymer chain now has the same effective conjugation length.

0015Furthermore, in contrast to other aromatic units that cannot form quinoidal type delocalisation, such as meta-substituted benzenes, or 2,7-substituted naphthalene's, thieno[2,3-b]thiophene has a linear shape and does not introduce 'kinks' in the polymer backbone. Such 'kinks' can result in amorphous polymers.

0016<nplcit id="ncit0004" npl-type="s"><text>G. Koßmehl et al., Makromol. Chem. 1982,183, 2747-2769</text></nplcit> disclose poly(thieno[2,3-b]thiophene-2,5-divinylenearylene), wherein the arylene group is 2,5-thiophene, 1,4-phenylene or 2,5-dimethoxy-1,4-phenylene. However, copolymers of this type with a vinyl linker do often show stability problems, and copolymers comprising unsubstituted or methoxy substituted phenylene groups often have low solubility.

0017<patcit id="pcit0001" dnum="EP1300430A"><text>EP-A-1 300 430</text></patcit>, <patcit id="pcit0002" dnum="EP1275651A"><text>EP-A-1 275 651</text></patcit> and <patcit id="pcit0003" dnum="EP0144013A"><text>EP-A-0 144 013</text></patcit> disclose polymers comprising thiophene moieties for use as semiconductors, but do neither disclose nor suggest the compounds of the present invention.

Summary of the Invention

0018The invention relates to mono-, oligo- and polymers, characterized in that they are compounds of formula I1         R³-[(A)_a-(B)_b-(C)_c-(D)_d]_nR⁴   I1 wherein <dl id="dl0001"><dt>A and C</dt><dd>denote independently of each other, and each of A and C in case of multiple occurrence independently of one another, a group of formula II <chemistry id="chem0003" num="0003"><img file="EP1510535B1_D0003.tif" /></chemistry></dd><dt>R¹ and R²</dt><dd>are independently of each other H, halogen or straight chain, branched or cyclic alkyl with 1 to 20 C-atoms, which may be unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, it being also possible for one or more non-adjacent CH₂ groups to be replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR⁰-, -SiR⁰R⁰⁰-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -CH=CH- or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another, or denotes optionally substituted aryl or heteroaryl, P-Sp- or P*-Sp-,</dd><dt>R³ and R⁴</dt><dd>are independently of each other H, halogen, Sn(R⁰)₃ , B(OR⁰)₂, CH₂Cl, COH, CH=CH₂, SiR⁰R⁰⁰R⁰⁰⁰, optionally substituted aryl or heteroaryl, P-Sp- or P*-Sp-,</dd><dt>P</dt><dd>is a polymerisable group that is capable of participating in a polymerisation reaction or capable of being grafted to a polymer backbone in a polymeranaloguous reaction,</dd><dt>P*</dt><dd>is a group that can be converted to or substituted by a polymerisable or reactive group P,</dd><dt>Sp</dt><dd>is a spacer group or a single bond,</dd><dt>R⁰ and R⁰⁰</dt><dd>are independently of each other H, aryl or alkyl with 1 to 12 C-atoms,</dd><dt>B and D</dt><dd>are independently of each other, and each of B and D in case of multiple occurrence independently of one another, an arylene or heteroarylene group that is optionally substituted with one or more groups R¹,</dd><dt>a, b, c, d</dt><dd>are independently of each other 0 or an integer from 1 to 10, with a + b + c + d > 0, and wherein in at least one recurring unit [A)_a-(B)_b-(C)_c-(D)_d] at least one of a and c is 1 and at least one of b and d is 1, and</dd><dt>n</dt><dd>is an integer ≥ 1,</dd></dl> wherein the recurring units [(A)_a-(B)_b-(C)_c-(D)_d] can be identical or different, and wherein, if n is 1, one or both of R³ and R⁴ are P-Sp or P*-Sp-.

0019The invention further relates to a semiconductor or charge transport material, component or device comprising at least one mono-, oligo- or polymer as defined above.

0020The invention further relates to the use of polymers according to the invention as semiconductors or charge transport materials, in particular in optical, electrooptical or electronic devices, like for example in field effect transistors (FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications such as electroluminescent displays or backlights of e.g. liquid crystal displays (LCD), for photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors and for electrophotographic applications like electrophotographic recording.

0021The invention further relates to the use of the novel mono-, oligo- and polymers according to the present invention as electroluminescent materials, in photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors, for electrophotographic applications like electrophotographic recording and as alignment layer in LCD or OLED devices.

0022The invention further relates to an optical, electrooptical or electronic device, FET, integrated circuit (IC), TFT, OLED or alignment layer comprising a semiconducting or charge transport material, component or device according to the invention.

0023The invention further relates to a TFT or TFT array for flat panel displays, radio frequency identification (RFID) tag, electroluminescent display or backlight comprising a semiconducting or charge transport material, component or device or a FET, IC, TFT or OLED according to the invention.

0024The invention further relates to a security marking or device comprising a FET or an RFID tag according to the invention.

Brief Description of the Drawings

0025<ul id="ul0001" list-style="none"><li><figref idref="f0001"><b>Figure 1</b></figref> shows the UV spectra of polymers according to the present invention.</li><li><figref idref="f0002"><b>Figure 2</b></figref> shows the UV spectrum of a polymer according to prior art.</li><li><figref idref="f0003"><b>Figures 3a</b></figref> and <figref idref="f0004"><b>3b</b></figref> show the transfer and output characteristics of an OFET comprising a polymer according to the present invention.</li></ul>

Detailed Description of the Invention

0026The mono-, oligo and polymers according to the invention are especially useful as charge transport semiconductors in that they have high carrier mobilities. Particularly preferred are polymers wherein the thieno[2,3-b]thiophene group is unsubstituted or substituted by one or more alkyl groups. The introduction of alkyl side chains into the thienothiophene group improves their solubility and therefore their solution processibility.

0027Copolymerisation of the thieno[2,3-b]thiophene core with functionalised aromatic or unsaturated comonomers can further improve the solubility and the charge transport properties. Variation of the aromatic comonomers provides a method of tailoring the band gap of the polymers. This will lead to better stability and higher charge carrier mobility.

0028In the oligo- and polymers of the present invention the recurring units [(A)_a-(B)_b-(C)_c-(D)_d] in case of multiple occurrence can be selected of formula I independently of each other, so that an oligo- or polymer may comprise identical or different recurring units [(A)_a-(B)_b-(C)_c-(D)_d]. The oligo- and polymers thus include homopolymers and copolymers like for example <ul id="ul0002" list-style="dash"><li>statistically random copolymers, for example with a monomer sequence such as -A-B-C-C-B-D-A-B-D- or -A-C-A-A-C-,</li><li>alternating copolymers, for example with a monomer sequence such as -A-B-C-D-A-B-C-D- or -A-B-C-A-B-C-, and</li><li>block copolymers, for example with a monomer sequence such as - A-A-B-B-B-B-C-C-C-D-D-D-, wherein the groups A, B, C and D preferably together form a conjugated system, and wherein multiple groups (for example each group B in the sequence -B-B-B-B-B-) can be identical or different from one another.</li></ul>

0029Especially preferred are mono-, oligo- and polymers comprising one or more recurring units [(A)_a-(B)_b-(C)_c-(D)_d], wherein a is 1, c is 0 and b or d is an integer from 1 to 10, preferably 1, 2, 3, 4, 5 or 6, very preferably consisting exclusively of such recurring units.

0030Further preferred are mono-, oligo-, and polymers of formula I1 having identical recurring units.

0031Further preferred are mono-, oligo-, and polymers of formula I1 wherein R¹ and R² are identical groups.

0032Further preferred are mono-, oligo-, and polymers of formula I1 having a degree of polymerisation (number n of recurring units) from 2 to 5000, in particular from 10 to 5000, very preferably from 100 to 1000.

0033Further preferred are mono-, oligo-, and polymers of formula I1 having a molecular weight from 5000 to 30,000 , in particular from 20,000 to 100,000.

0034Further preferred are mono-, oligo- and polymers of formula I1 comprising at least one reactive group P that is capable of a polymerisation or crosslinking reaction.

0035Further preferred are mono-, oligo- and polymers of formula I1 that are mesogenic or liquid crystalline, in particular polymers forming calamitic phases, and reactive mesogens of formula I1 comprising one or more groups P-Sp-, forming calamitic phases.

0036Further preferred are mono-, oligo- and polymers of formula I1 wherein at least one of B and D is arylene or heteroarylene that is optionally substituted by one or more groups L.

0037L is F, Cl, Br, or an alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 20 C atoms, wherein one or more H atoms are optionally replaced by F or Cl, further C₁-C₂₀-alkyl that is optionally substituted with one or more fluorine atoms, C₁-C₂₀-alkoxy, C₁-C₂₀-alkenyl, C₁-C₂₀-alkynyl, C₁-C₂₀-thioalkyl, C₁-C₂₀-silyl, C₁-C₂₀-ester, C₁-C₂₀-amino, C₁-C₂₀-fluoroalkyl, very preferably C₁-C₂₀-alkyl or C₁-C₂₀-fluoroalkyl.

0038Further preferred are mono-, oligo- and polymers of formula I1 shown above and below wherein <ul id="ul0003" list-style="dash"><li>one of b and d is 0,</li><li>b and d are independently of each other 0, 1, 2, 3 or 4,</li><li>a and c are independently of each other 0, 1 or 2,</li><li>B and/or D are C≡C or arylene or heteroarylene,</li><li>B and/or D is CX¹=CX², wherein preferably at least one of X¹ and X² is different from H.</li><li>B and/or D is thiophene-2,5-diyl that is optionally mono- or polysubstituted by L as defined above,</li><li>B and/or D is thieno[3,2-b]thiophene that is optionally mono- or polysubstituted by L as defined above,</li><li>B and/or D is selected of formula III <chemistry id="chem0004" num="0004"><img file="EP1510535B1_D0004.tif" /></chemistry></li><li>wherein R⁵ and R⁶ have one of the meanings given for R¹ in formula I or of the preferred meanings below. Especially preferably R⁵ and R⁶ are alkyl or fluoroalkyl with 1 to 20 C-atoms.</li><li>n is an integer from 2 to 5000 and R¹ and R² are different from P-Sp- and P*-Sp,</li><li>R¹ and R² are selected from H or C₁-C₂₀-alkyl that is optionally substituted with one or more fluorine atoms, C₁-C₂₀-alkoxy, C₁-C₂₀-alkenyl, C₁-C₂₀-alkynyl, C₁-C₂₀-thioalkyl, C₁-C₂₀-silyl, C₁-C₂₀-ester, C₁-C₂₀-amino, C₁-C₂₀-fluoroalkyl, and optionally substituted aryl or heteroaryl, very preferably C₁-C₂₀-alkyl or C₁-C₂₀-fluoroalkyl,</li><li>n is 1 and one or both of R³ and R⁴ are P-Sp- or P^*-Sp-,</li><li>P* is -OH or -O-Si-R⁰R⁰⁰R⁰⁰⁰, preferably wherein R⁰, R⁰⁰ and R⁰⁰⁰ are identical or different groups selected from aryl or C_1-12-alkyl, preferably C₁-C₆-alkyl, like methyl, ethyl, isopropyl, tert-butyl or phenyl,</li><li>R³ and R⁴ are selected from H, halogen, Sn(R⁰)₃ , CH₂Cl, COH, CH=CH₂, SiR⁰R⁰⁰R⁰⁰⁰ and optionally substituted aryl or heteroaryl,</li><li>n ≥ 1.</li></ul>

0039Copolymers according to the present invention wherein one or more of B and D are acetylene or arylene or heteroarylene have the following advantages: <ul id="ul0004" list-style="dash" compact="compact"><li>improved solubility through the use of side chains of the aryl co-polymers,</li><li>larger molecular weights, which leads to better processability.</li><li>improved packing by interdigitation of side-chains, which leads to liquid crystalline or crystalline polymers that facilitate charge transport.</li></ul>

0040If B or D is arylene or heteroarylene, it is preferably a mono-, bi- or tricyclic aromatic or heteroaromatic group with up to 25 C atoms, wherein the rings can be fused, and in which the heteroaromatic group contains at least one hetero ring atom, preferably selected from N, O and S. It is optionally substituted with one or more of F, Cl, Br, I, CN, and straight chain, branched or cyclic alkyl having 1 to 20 C atoms, which is unsubstituted, mono- or poly-substituted by F, Cl, Br, I, -CN or -OH, and in which one or more non-adjacent CH₂ groups are optionally replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR⁰-, -SiR⁰R⁰⁰-, -CO-, -COO-, OCO-, -OCO-O, -S-CO-, -CO-S-,-CH=CH- or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another.

0041Preferred arylene or heteroarylene groups are selected from phenyl in which, in addition, one or more CH groups may be replaced by N, or naphthalene, alkyl fluorene or oxazole, thiophene, thienothiophene and dithienothiophene, wherein all these groups are optionally mono- or polysubstituted with L as defined above.

0042Especially preferred arylene or heteroarylene groups groups are 1,4-phenylene, fluorinated 1,4-phenylene, 2,5-pyridine, 2,5-pyrimidine, p,p'-biphenyl, naphthalene-2,6-diyl, thiophene-2,5-diyl, fluorinated or alkylated thiophene-2,5-diyl, 2,2-dithiophene, fluorinated or alkylated 2,2-dithiophene, [3,2-b]thiophene-2,5-diyl, fluorinated or alkylated thieno[3,2-b]thiophene-2,5-diyl, fluorinated benzo[1,2-b:4,5-b']dithiophene, 2,5-thiazole, 2,5-thiadiazole, 2,5-oxazole and 2,5-oxadiazole, all of which are unsubstituted, mono- or polysubstituted with L as defined above.

0043If one of R^1-4 is aryl or heteroaryl, it is preferably a mono-, bi- or tricyclic aromatic or heteroaromatic group with up to 25 C atoms, wherein the rings can be fused, and in which the heteroaromatic group contains at least one hetero ring atom, preferably selected from N, O and S. It is optionally substituted with one or more of F, Cl, Br, I, CN, and straight chain, branched or cyclic alkyl having 1 to 20 C atoms, which is unsubstituted, mono- or poly-substituted by F, Cl, Br, I, -CN or -OH, and in which one or more non-adjacent CH₂ groups are optionally replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR⁰-, -SiR⁰R⁰⁰-, -CO-, -COO-, OCO-, -OCO-O, -S-CO-, -CO-S-,-CH=CH- or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another.

0044Especially preferred aryl and heteroaryl groups are phenyl, fluorinated phenyl, pyridine, pyrimidine, biphenyl, naphthalene, optionally fluorinated or alkylated or fluoroalkylated benzo[1,2-b:4,5-b']dithiophene, optionally fluorinated or alkylated or fluoroalkylated thieno[3,2-b]thiophene, optionally fluorinated or alkylated or fluoroalkylated 2,2-dithiophene, thiazole and oxazole, all of which are unsubstituted, mono- or polysubstituted with L as defined above.

0045If one of R^1-4 is an alkyl or alkoxy radical, i.e. where the terminal CH₂ group is replaced by -O-, this may be straight-chain or branched. It is preferably straight-chain, has 2 to 8 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.

0046Fluoroalkyl or fluorinated alkyl or alkoxy is preferably straight chain (O)C_iF_2i+1, wherein i is an integer from 1 to 20, in particular from 1 to 15, very preferably (O)CF₃, (O)C₂F₅, (O)C₃F₇, (O)C₄F₉, (O)C₅F₁₁, (O)C₆F₁₃, (O)C₇F₁₅ or (O)C₈F₁₇, most preferably (O)C₆F₁₃.

0047CX¹=CX² is preferably -CH=CH-, -CH=CF-, -CF=CH-, -CF=CF-, -CH=C(CN)- or -C(CN)=CH-.

0048Halogen is preferably F, Br or Cl.

0049Hetero atoms are preferably selected from N, O and S.

0050The reactive or polymerisable group P is a group that is capable of participating in a polymerisation reaction, like radicalic or ionic chain polymerisation, polyaddition or polycondensation, or capable of being grafted, for example by condensation or addition, to a polymer backbone in a polymeranaloguous reaction. Especially preferred are polymerisable groups for chain polymerisation reactions, like radicalic, cationic or anionic polymerisation. Very preferred are polymerisable groups comprising a C-C double or triple bond, and polymerisable groups capable of polymerisation by a ring-opening reaction, like oxetanes or epoxides.

0051The polymerisable or reactive group P is preferably selected from CH₂=CW¹-COO-, <chemistry id="chem0005" num="0005"><img file="EP1510535B1_D0005.tif" /></chemistry><chemistry id="chem0006" num="0006"><img file="EP1510535B1_D0006.tif" /></chemistry> , CH₂=CW²-(O)_k1-, CH₃-CH=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH-CH₂)₂N-, HO-CW²W³-, HS-CW²W³-, HW²N-, HO-CW²W³-NH-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)_k1-Phe-(O)_k2-, Phe-CH=CH-, HOOC-, OCN-, and W⁴W⁵W⁶Si-, with W¹ being H, Cl, CN, phenyl or alkyl with 1 to 5 C-atoms, in particular H, Cl or CH₃, W² and W³ being independently of each other H or alkyl with 1 to 5 C-atoms, in particular methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ being independently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phe being 1,4-phenylene and k₁ and k₂ being independently of each other 0 or 1.

0052Especially preferred groups P are CH₂=CH-COO-, CH₂=C(CH₃)-COO-, CH₂=CH-, CH₂=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH)₂CH-O-, and <chemistry id="chem0007" num="0007"><img file="EP1510535B1_D0007.tif" /></chemistry>

0053Very preferred are acrylate and oxetane groups. Oxetanes produce less shrinkage upon polymerisation (cross-linking), which results in less stress development within films, leading to higher retention of ordering and fewer defects. Oxetane cross-linking also requires cationic initiator, which unlike free radical initiator is inert to oxygen.

0054As for the spacer group Sp all groups can be used that are known for this purpose to the skilled in the art. The spacer group Sp is preferably of formula Sp'-X, such that P-Sp- is P-Sp'-X- and P*-Sp- is P*-Sp'-X-, wherein <dl id="dl0002" compact="compact"><dt>Sp'</dt><dd>is alkylene with up to 20 C atoms which may be unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, it being also possible for one or more non-adjacent CH₂ groups to be replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR⁰-, -SiR⁰R⁰⁰-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -CH=CH- or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another,</dd><dt>X</dt><dd>is -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR⁰-, -NR⁰-CO- , -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, - SCF₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰-, -CX¹=CX²-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, and</dd></dl>

0055R⁰, R⁰⁰, X¹ and X² have one of the meanings given above.

0056X is preferably -O-, -S-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CH₂CH₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰-, -CX¹=CX²-, -C≡C- or a single bond, in particular -O-, -S-, -C≡C-, -CX¹=CX²- or a single bond, very preferably a group that is able to from a conjugated system, such as -C≡C- or -CX¹=CX²-, or a single bond.

0057Typical groups Sp' are, for example, -(CH₂)_p-, -(CH₂CH₂O)_q-CH₂CH₂-, -CH₂CH₂-S-CH₂CH₂- or -CH₂CH₂-NH-CH₂CH₂- or -(SiR⁰R⁰⁰-O)_p-, with p being an integer from 2 to 12, q being an integer from 1 to 3 and R⁰ and R⁰⁰ having the meanings given above.

0058Preferred groups Sp' are ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylene-thioethylene, ethylene-N-methyl-iminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene for example.

0059Further preferred are compounds with one or two groups P-Sp- or P*-Sp- wherein Sp is a single bond.

0060In case of compounds with two groups P-Sp or P*-Sp-, respectively, each of the groups P or P* and the spacer groups Sp can be identical or different.

0061Another preferred embodiment relates to compounds comprising one or more groups P*-Sp-, wherein P* is a group that can be converted to or substituted by a polymerisable or reactive group P as defined above. Preferably P* is a group that is less reactive than P, for example towards spontaneous polymerisation. These compounds can be used for example as intermediates in the synthesis of polymerisable compounds of formula I1 having one or more groups P, or as a precursor material for polymerisable compounds which are too reactive to be stored or transported for longer periods of time. The group P* is preferably chosen such that it can easily be transformed into or substituted by a group P by known methods. For example, it can be a protected form of group P. Further preferred groups P* are for example -OH or silyl groups like -O-Si-R⁰R⁰⁰R⁰⁰⁰, for example -O-Si(CH₃)₃, -O-Si-(isopropyl)₃, -O-Si-(phenyl)₃, -O-Si-(CH₃)₂(phenyl), -O-Si(CH₃)₂(tert-butyl) or the like, which can be reacted e.g. into polymerisable (meth)acrylate end groups.

0062SCLCPs obtained from the inventive compounds or mixtures by polymerisation or copolymerisation have a backbone that is formed by the polymerisable group P.

0063Especially preferred are mono-, oligo- and polymers selected from the following formulae <chemistry id="chem0008" num="0008"><img file="EP1510535B1_D0008.tif" /></chemistry><chemistry id="chem0009" num="0009"><img file="EP1510535B1_D0009.tif" /></chemistry><chemistry id="chem0010" num="0010"><img file="EP1510535B1_D0010.tif" /></chemistry><chemistry id="chem0011" num="0011"><img file="EP1510535B1_D0011.tif" /></chemistry><chemistry id="chem0012" num="0012"><img file="EP1510535B1_D0012.tif" /></chemistry><chemistry id="chem0013" num="0013"><img file="EP1510535B1_D0013.tif" /></chemistry><chemistry id="chem0014" num="0014"><img file="EP1510535B1_D0014.tif" /></chemistry><chemistry id="chem0015" num="0015"><img file="EP1510535B1_D0015.tif" /></chemistry><chemistry id="chem0016" num="0016"><img file="EP1510535B1_D0016.tif" /></chemistry><chemistry id="chem0017" num="0017"><img file="EP1510535B1_D0017.tif" /></chemistry><chemistry id="chem0018" num="0018"><img file="EP1510535B1_D0018.tif" /></chemistry><chemistry id="chem0019" num="0019"><img file="EP1510535B1_D0019.tif" /></chemistry><chemistry id="chem0020" num="0020"><img file="EP1510535B1_D0020.tif" /></chemistry> wherein R¹, R² and n have the meanings of formula I1 and R⁵ and R⁶ have one of the meanings of formula III or the preferred meanings above. Especially preferably R¹, R², R⁵ and R⁶ in these formulae are alkyl or fluoroalkyl with 1 to 20 C-atoms.

0064Further preferred are the following monomeric compounds <chemistry id="chem0021" num="0021"><img file="EP1510535B1_D0021.tif" /></chemistry><chemistry id="chem0022" num="0022"><img file="EP1510535B1_D0022.tif" /></chemistry><chemistry id="chem0023" num="0023"><img file="EP1510535B1_D0023.tif" /></chemistry><chemistry id="chem0024" num="0024"><img file="EP1510535B1_D0024.tif" /></chemistry><chemistry id="chem0025" num="0025"><img file="EP1510535B1_D0025.tif" /></chemistry><chemistry id="chem0026" num="0026"><img file="EP1510535B1_D0026.tif" /></chemistry> wherein R¹, R² and Sp are as defined in formula I1, P' is P or P* as defined in formula I1, and R' has one of the meanings of R³ given in formula I1.

0065The mono-, oligo- and polymers of the present invention can be synthesized according to or in analogy to known methods. Some preferred methods are described below.

0066The di-esters of thieno[2,3-b]thiophene are synthesised according to literature methods as shown in Scheme 1 [see <nplcit id="ncit0005" npl-type="s"><text>A. Comel; G. Kirsch, J. Heterocyclic Chem, 2001, 38, 1167-1171</text></nplcit>]. Therefore an active methylene compound such as malonitrile or penta-2,4-dione is reacted with carbon disulfide and ethyl bromoacetate in the presence of base affords the thieno-2,3-b-thiophene ring. Longer aliphatic chains can readily by introduced onto the core by varying the active methylene compound used. For the unsubstituted compound, the amino groups are removed by diazotisation and subsequent treatment with hypophosphorous acid. Finally the ester groups are hydrolysed to the corresponding carboxylic acids, and these are converted directly to the aromatic bromides by treatment with NBS in the presence of sodium hydroxide. An alternative route to the unsubstituted thieno[2,3-b]thiophene core is depected in Scheme 2. Commercially available thiophene-2-thiol is alklylated with bromoacetaldehyde dimethyl acetal and the resulting protected aldehyde in deprotected and cyclised to the product in one-pot by treatment with polyphosphoric acid in refluxing chlorobenzene. Unsubstituted thieno[2,3-b]thiophene can readily be converted to the 2,5-dibromo or 2,5-diiodothieno[2,3-b]thiophene by lithiation with two equivalents of a halogenating agent. 2-Bromo-5-iodo-thieno[2,3-b]thiophene can be prepared by a sequential two step electrophillic bromination and iodination as depected in Scheme 3. <chemistry id="chem0027" num="0027"><img file="EP1510535B1_D0027.tif" /></chemistry><chemistry id="chem0028" num="0028"><img file="EP1510535B1_D0028.tif" /></chemistry><chemistry id="chem0029" num="0029"><img file="EP1510535B1_D0029.tif" /></chemistry><chemistry id="chem0030" num="0030"><img file="EP1510535B1_D0030.tif" /></chemistry>

0067The dihalo intermediates are then reacted with thiophene boronic acids under cross-coupling conditions, or with thiophene organozinc reagents in the presence of palladium catalyst to afford the bis(thiophene) intermediates, as shown in Scheme 4. These are subsequently polymerised oxidatively by treatment with ferric chloride to afford polymers of reasonable molecular weight (Mw =14,000 - 23,000). <chemistry id="chem0031" num="0031"><img file="EP1510535B1_D0031.tif" /></chemistry><chemistry id="chem0032" num="0032"><img file="EP1510535B1_D0032.tif" /></chemistry>

0068Other co-polymers are readily formed by reaction of a 2,5-dihalothieno[2,3-b]thiophene with, for example, a bis(boronic) ester or acid under Suzuki conditions (see <nplcit id="ncit0006" npl-type="s"><text>M. Jayakannan, J.L.J. van Dongen, R.A.J. Janssen, Macromolecules, 2001, 34, p5386-5393</text></nplcit>)) or a bis(organo)tin reagent under Stille conditions (see <nplcit id="ncit0007" npl-type="s"><text>B. Tsuie et al, J. Mater. Chem., 1999, 9, p2189-2200</text></nplcit>), as shown in Scheme 5. The methodology can be reversed so that the bis(boronic) ester or acid of thieno[2,3-b]thiophene, or the bis(organo)tin reagent of thieno[2,3-b]thiophene is reacted with a dihalo aromatic compound (Scheme 5). By modifying the ratio of the starting reagents, the percentage incorporation of the thieno-2,3-thiophene, and hence the HOMO level, can easily be modified, as seen in Scheme 6. <chemistry id="chem0033" num="0033"><img file="EP1510535B1_D0033.tif" /></chemistry><chemistry id="chem0034" num="0034"><img file="EP1510535B1_D0034.tif" /></chemistry><b>OR</b>: <chemistry id="chem0035" num="0035"><img file="EP1510535B1_D0035.tif" /></chemistry><chemistry id="chem0036" num="0036"><img file="EP1510535B1_D0036.tif" /></chemistry> wherein Ar has one of the meanings of B given in formula I.

0069Thieno-2,3-b-thiophene is also readily incorporated into regioregular poly(alkyl)thiophene, and this provides a means to improve the air-stability of that polymer without adversely affecting the close-packed morphology which contributes to such high charge carrier mobilities for PAT. The method of synthesis is outlined in scheme 7, as is based upon the route described by McCullough et al. [see<nplcit id="ncit0008" npl-type="s"><text> S. M. K. Robert S. Loewe, and; R. D. McCullough*, Adv. Mater., 1999, 11, 250</text></nplcit>]. Therefore the mono-Grignard reagent of 2,5-dibromo-3-alkylthiophene and thieno-2,3-b-thiophene are formed in separate flask by treatment with 1 equivalent of an alkyl Grignard reagent or by treatment with magnesium metal. These 2 reagents are then premixed and treated with a catalytic amount of nickel to initiate polymerisation. Both reagents have similar reactivity and the thieno-2,3-b-thiophene is incorporated randomly along the backbone. A typical ratio would be 5-20%. <chemistry id="chem0037" num="0037"><img file="EP1510535B1_D0037.tif" /></chemistry>

0070A further aspect of the invention relates to both the oxidised and reduced form of the compounds and materials according to this invention. Either loss or gain of electrons results in formation of a highly delocalised ionic form, which is of high conductivity. This can occur on exposure to common dopants. Suitable dopants and methods of doping are known to those skilled in the art, e.g. from <patcit id="pcit0004" dnum="EP0528662A"><text>EP 0 528 662</text></patcit>, <patcit id="pcit0005" dnum="US5198153A"><text>US 5,198,153</text></patcit> or <patcit id="pcit0006" dnum="WO9621659A"><text>WO 96/21659</text></patcit>.

0071The doping process typically implies treatment of the semiconductor material with an oxidating or reducing agent in a redox reaction to form delocalised ionic centres in the material, with the corresponding counterions derived from the applied dopants. Suitable doping methods comprise for example exposure to a doping vapor in the atmospheric pressure or at a reduced pressure, electrochemical doping in a solution containing a dopant, bringing a dopant into contact with the semiconductor material to be thermally diffused, and ion-implantantion of the dopant into the semiconductor material.

0072When electrons are used as carriers, suitable dopants are for example halogens (e.g., I₂, Cl₂, Br₂, ICl, ICl₃, IBr and IF), Lewis acids (e.g., PF₅, AsF₅, SbF₅, BF₃, BCl₃, SbCl₅, BBr₃ and SO₃), protonic acids, organic acids, or amino acids (e.g., HF, HCl, HNO₃, H₂SO₄, HClO₄, FSO₃H and ClSO₃H), transition metal compounds (e.g., FeCl₃, FeOCl, Fe(ClO₄)₃, Fe(4-CH₃C₆H₄SO₃)₃, TiCl₄, ZrCl₄, HfCl₄, NbF₅, NbCl₅, TaCl₅, MoF₅, MoCl₅, WF₅, WCl₆, UF₆ and LnCl₃ (wherein Ln is a lanthanoid), anions (e.g., Cl^-, Br^-, I^-, I₃^-, HSO₄^-, SO₄^2-, NO₃^-, ClO₄^-, BF₄^-, PF₆^-, AsF₆^-, SbF₆^-, FeCl₄^-, Fe(CN)₆^3-, and anions of various sulfonic acids, such as aryl-SO₃^-). When holes are used as carriers, examples of dopants are cations (e.g., H⁺, Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺), alkali metals (e.g., Li, Na, K, Rb, and Cs), alkaline-earth metals (e.g., Ca, Sr, and Ba), O₂, XeOF₄, (NO₂⁺) (SbF₆^-), (NO₂⁺) (SbCl₆^-), (NO₂⁺) (BF₄^-), AgClO₄, H₂IrCl₆, La(NO₃)₃^· 6H₂O, FSO₂OOSO₂F, Eu, acetylcholine, R₄N⁺, (R is an alkyl group), R₄P⁺ (R is an alkyl group), R₆As⁺ (R is an alkyl group), and R₃S⁺ (R is an alkyl group).

0073The conducting form of the compounds and materials of the present invention can be used as an organic "metal" in applications, for example, but not limited to, charge injection layers and ITO planarising layers in organic light emitting diode applications, films for flat panel displays and touch screens, antistatic films, printed conductive substrates, patterns or tracts in electronic applications such as printed circuit boards and condensers.

0074A preferred embodiment of the present invention relates to mono-, oligo- and polymers of formula I1 and its preferred subformulae that are mesogenic or liquid crystalline, and very preferably comprise one or more polymerisable groups. Very preferred materials of this type are monomers and oligomers of formula I1 and its preferred subformulae wherein n is an integer from 1 to 15 and R³ and/or R⁴ denote P-Sp-.

0075These materials are particularly useful as semiconductors or charge transport materials, as they can be aligned into uniform highly ordered orientation in their liquid crystal phase by known techniques, thus exhibiting a higher degree of order that leads to particularly high charge carrier mobility. The highly ordered liquid crystal state can be fixed by in situ polymerisation or crosslinking via the groups P to yield polymer films with high charge carrier mobility and high thermal, mechanical and chemical stability.

0076For example, if a device is made from a polymerisable liquid crystal material by polymerisation in situ, the liquid crystal material preferably comprises one or more mono- or oligomers of formula I1 and its preferred subformulae wherein one or both of R³ and R⁴ denote P-Sp-. If a liquid crystal polymer is preapred first, for example by polymerisation in solution, and the isolated polymer is used to make the device, the polymer is preferably made from a liquid crystal material comprising one or more mono- or oligomers of formula I1 and its preferred subformulae wherein one of R³ and R⁴ denotes P-Sp-.

0077It is also possible to copolymerise the polymerisable mono-, oligo- and polymers according to the present invention with other polymerisable mesogenic or liquid crystal monomers that are known from prior art, in order to induce or enhance liquid crystal phase behaviour.

0078Thus, another aspect of the invention relates to a polymerisable liquid crystal material comprising one or more mono-, oligo- or polymers of the present invention as described above and below comprising at least one polymerisable group, and optionally comprising one or more further polymerisable compounds, wherein at least one of the polymerisable mono-, oligo- and polymers of the present invention and/or the further polymerisable compounds is mesogenic or liquid crystalline.

0079Particularly preferred are liquid crystal materials having a nematic and/or smectic phase. For FET applications smectic materials are especially preferred. For OLED applications nematic or smectic materials are especially preferred.

0080Another aspect of the present invention relates to an anisotropic polymer film with charge transport properties obtainable from a polymerisable liquid crystal material as defined above that is aligned in its liquid crystal phase into macroscopically uniform orientation and polymerised or crosslinked to fix the oriented state.

0081Preferably polymerisation is carried out as in-situ polymerisation of a coated layer of the material, preferably during fabrication of the electronic or optical device comprising the inventive semiconductor material. In case of liquid crystal materials, these are preferably aligned in their liquid crystal state into homeotropic orientation prior to polymerisation, where the conjugated pi-electron systems are orthogonal to the direction of charge transport. This ensures that the intermolecular distances are minimised and hence then energy required to transport charge between molecules is minimised. The molecules are then polymerised or crosslinked to fix the uniform orientation of the liquid crystal state. Alignment and curing are carried out in the liquid crystal phase or mesophase of the material. This technique is known in the art and is generally described for example in <nplcit id="ncit0009" npl-type="s"><text>D.J. Broer, et al., Angew. Makromol. Chem. 183, (1990), 45-66</text></nplcit>

0082Alignment of the liquid crystal material can be achieved for example by treatment of the substrate onto which the material is coated, by shearing the material during or after coating, by application of a magnetic or electric field to the coated material, or by the addition of surface-active compounds to the liquid crystal material. Reviews of alignment techniques are given for example by<nplcit id="ncit0010" npl-type="b"><text> I. Sage in "Thermotropic Liquid Crystals", edited by G. W. Gray, John Wiley &amp; Sons, 1987, pages 75-77</text></nplcit>, and by <nplcit id="ncit0011" npl-type="b"><text>T. Uchida and H. Seki in "Liquid Crystals - Applications and Uses Vol. 3", edited by B. Bahadur, World Scientific Publishing, Singapore 1992, pages 1-63</text></nplcit>. A review of alignment materials and techniques is given by <nplcit id="ncit0012" npl-type="s"><text>J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 1-77</text></nplcit>.

0083Polymerisation takes place by exposure to heat or actinic radiation. Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays or irradiation with high energy particles, such as ions or electrons. Preferably polymerisation is carried out by UV irradiation at a non-absorbing wavelength. As a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced. Another possible source for actinic radiation is a laser, like e.g. a UV laser, an IR laser or a visible laser.

0084Polymerisation is preferably carried out in the presence of an initiator absorbing at the wavelength of the actinic radiation. For example, when polymerising by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or ions that start the polymerisation reaction. When curing polymerisable materials with acrylate or methacrylate groups, preferably a radical photoinitiator is used, when curing polymerisable materials with vinyl, epoxide and oxetane groups, preferably a cationic photoinitiator is used. It is also possible to use a polymerisation initiator that decomposes when heated to produce free radicals or ions that start the polymerisation. As a photoinitiator for radical polymerisation for example the commercially available Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (all from Ciba Geigy AG) can be used, whereas in case of cationic photopolymerisation the commercially available UVI 6974 (Union Carbide) can be used.

0085The polymerisable material can additionally comprise one or more other suitable components such as, for example, catalysts, sensitizers, stabilizers, inhibitors, chain-transfer agents, co-reacting monomers, surface-active compounds, lubricating agents, wetting agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes or pigments.

0086Mono-, oligo- and polymers comprising one or more groups P-Sp- can also be copolymerised with polymerisable mesogenic compounds to induce or enhance liquid crystal phase behaviour. Polymerisable mesogenic compounds that are suitable as comonomers are known in prior art and disclosed for example in <patcit id="pcit0007" dnum="WO9322397A"><text>WO 93/22397</text></patcit>; <patcit id="pcit0008" dnum="EP0261712A"><text>EP 0,261,712</text></patcit>; <patcit id="pcit0009" dnum="DE19504224"><text>DE 195,04,224</text></patcit>; <patcit id="pcit0010" dnum="WO9522586A"><text>WO 95/22586</text></patcit> and <patcit id="pcit0011" dnum="WO9700600A"><text>WO 97/00600</text></patcit>.

0087Another aspect of the invention relates to a liquid crystal side chain polymer (SCLCP) obtained from a polymerisable liquid crystal material as defined above by polymerisation or polymeranaloguous reaction. Particularly preferred are SCLCPs obtained from one or more monomers of formula I1 and its preferred subformulae wherein one or both, preferably one, of R³ and R⁴ are a polymerisable or reactive group, or from a polymerisable mixture comprising one or more of said monomers.

0088Another aspect of the invention relates to an SCLCP obtained from one or more monomers of formula 11 and its preferred subformulae wherein one or both of R³ and R⁴ are a polymerisable group, or from a polymerisable liquid crystal mixture as defined above, by copolymerisation or polymeranaloguous reaction together with one or more additional mesogenic or non-mesogenic comonomers.

0089Side chain liquid crystal polymers or copolymers (SCLCPs), in which the semiconducting component is located as a pendant group, separated from a flexible backbone by an aliphatic spacer group, offer the possibility to obtain a highly ordered lamellar like morphology. This structure consists of closely packed conjugated aromatic mesogens, in which very close (typically &lt; 4 Å) pi-pi stacking can occur. This stacking allows intermolecular charge transport to occur more easily, leading to high charge carrier mobilities. SCLCPs are advantageous for specific applications as they can be readily synthesized before processing and then e.g. be processed from solution in an organic solvent. If SCLCPs are used in solutions, they can orient spontaneously when coated onto an appropriate surface and when at their mesophase temperature, which can result in large area, highly ordered domains.

0090SCLCPs can be prepared from the polymerisable compounds or mixtures according to the invention by the methods described above, or by conventional polymerisation techniques which are known to those skilled in the art, including for example radicalic, anionic or cationic chain polymerisation, polyaddition or polycondensation. Polymerisation can be carried out for example as polymerisation in solution, without the need of coating and prior alignment, or polymerisation in situ. It is also possible to form SCLCPs by grafting compounds according to the invention with a suitable reactive group, or mixtures thereof, to presynthesized isotropic or anisotropic polymer backbones in a polymeranaloguous reaction. For example, compounds with a terminal hydroxy group can be attached to polymer backbones with lateral carboxylic acid or ester groups, compounds with terminal isocyanate groups can be added to backbones with free hydroxy groups, compounds with terminal vinyl or vinyloxy groups can be added, e.g., to polysiloxane backbones with Si-H groups. It is also possible to form SCLCPs by copolymerisation or polymeranaloguous reaction from the inventive compounds together with conventional mesogenic or non mesogenic comonomers. Suitable comonomers are known to those skilled in the art. In principle it is possible to use all conventional comonomers known in the art that carry a reactive or polymerisable group capable of undergoing the desired polymer-forming reaction, like for example a polymerisable or reactive group P as defined above. Typical mesogenic comonomers are for example those mentioned in <patcit id="pcit0012" dnum="WO9322397A"><text>WO 93/22397</text></patcit>, <patcit id="pcit0013" dnum="EP0261712A"><text>EP 0 261 712</text></patcit>, <patcit id="pcit0014" dnum="DE19504224"><text>DE 195 04 224</text></patcit>, <patcit id="pcit0015" dnum="WO9522586A"><text>WO 95/22586</text></patcit>, <patcit id="pcit0016" dnum="WO9700600A"><text>WO 97/00600</text></patcit> and <patcit id="pcit0017" dnum="GB2351734A"><text>GB 2 351 734</text></patcit>. Typical non mesogenic comonomers are for example alkyl acrylates or alkyl methacrylates with alkyl groups of 1 to 20 C atoms, like methyl acrylate or methyl methacrylate.

0091The mono-, oligo- and polymers of the present invention are useful as optical, electronic and semiconductor materials, in particular as charge transport materials in field effect transistors (FETs), e.g., as components of integrated circuitry, ID tags or TFT applications. Alternatively, they may be used in organic light emitting diodes (OLEDs) in electroluminescent display applications or as backlight of, e.g., liquid crystal displays, as photovoltaics or sensor materials, for electrophotographic recording, and for other semiconductor applications.

0092Especially the oligomers and polymers according to the invention show advantageous solubility properties which allow production processes using solutions of these compounds. Thus films, including layers and coatings, may be generated by low cost production techniques, e.g., spin coating. Suitable solvents or solvent mixtures comprise alkanes and/ or aromatics, especially their fluorinated derivatives.

0093The materials of the present invention are useful as optical, electronic and semiconductor materials, in particular as charge transport materials in field effect transistors (FETs), as photovoltaics or sensor materials, for electrophotographic recording, and for other semiconductor applications. Such FETs, where an organic semiconductive material is arranged as a film between a gate-dielectric and a drain and a source electrode, are generally known, e.g., from <patcit id="pcit0018" dnum="US5892244A"><text>US 5,892,244</text></patcit>, <patcit id="pcit0019" dnum="WO0079617A"><text>WO 00/79617</text></patcit>, <patcit id="pcit0020" dnum="US5998804A"><text>US 5,998,804</text></patcit>, and from the references cited in the background and prior art chapter and listed below. Due to the advantages, like low cost production using the solubility properties of the compounds according to the invention and thus the processibility of large surfaces, preferred applications of these FETs are such as integrated circuitry, TFT-displays and security applications.

0094In security applications, field effect transistors and other devices with semiconductive materials, like transistors or diodes, may be used for ID tags or security markings to authenticate and prevent counterfeiting of documents of value like banknotes, credit cards or ID cards, national ID documents, licenses or any product with monetry value, like stamps, tickets, shares, cheques etc..

0095Alternatively, the mono-, oligo- and polymers according to the invention may be used in organic light emitting devices or diodes (OLEDs), e.g., in display applications or as backlight of e.g. liquid crystal displays. Common OLEDs are realized using multilayer structures. An emission layer is generally sandwiched between one or more electron-transport and/ or hole-transport layers. By applying an electric voltage electrons and holes as charge carriers move towards the emission layer where their recombination leads to the excitation and hence luminescence of the lumophor units contained in the emission layer. The inventive compounds, materials and films may be employed in one or more of the charge transport layers and/or in the emission layer, corresponding to their electrical and/ or optical properties. Furthermore their use within the emission layer is especially advantageous, if the compounds, materials and films according to the invention show electroluminescent properties themselves or comprise electroluminescent groups or compounds. The selection, characterization as well as the processing of suitable monomeric, oligomeric and polymeric compounds or materials for the use in OLEDs is generally known by a person skilled in the art, see, e.g., <nplcit id="ncit0013" npl-type="s"><text>Meerholz, Synthetic Materials, 111-112, 2000, 31-34</text></nplcit>, <nplcit id="ncit0014" npl-type="s"><text>Alcala, J. Appl. Phys., 88, 2000, 7124-7128</text></nplcit> and the literature cited therein.

0096According to another use, the inventive compounds, materials or films, especially those which show photoluminescent properties, may be employed as materials of light sources, e.g., of display devices such as described in <patcit id="pcit0021" dnum="EP0889350A1"><text>EP 0 889 350 A1</text></patcit> or by <nplcit id="ncit0015" npl-type="s"><text>C. Weder et al., Science, 279, 1998, 835-837</text></nplcit>.

0097According to another use, the inventive compounds, materials or films can be used alone or together with other materials in or as alignment layers in LCD or OLED devices, as described for example in <patcit id="pcit0022" dnum="US20030021913A"><text>US 2003/0021913</text></patcit>. The use of charge transport compounds according to the present invention can increase the electrical conductivity of the alignment layer. When used in an LCD, this increased electrical conductivity can reduce adverse residual dc effects in the switchable LCD cell and suppress image sticking or, for example in ferroelectric LCDs, reduce the residual charge produced by the switching of the spontaneous polarisation charge of the ferroelectric LCs. When used in an OLED device comprising a light emitting material provided onto the alignment layer, this increased electrical conductivity can enhance the electroluminescence of the light emitting material. The compounds or materials according to the present invention having mesogenic or liquid crystalline properties can form oriented anisotropic films as described above, which are especially useful as alignment layers to induce or enhance alignment in a liquid crystal medium provided onto said anisotropic film. The materials according to the present invention may also be combined with photoisomerisable compounds and/or chromophores for use in or as photoalignment layers, as described in <patcit id="pcit0023" dnum="US20030021913A"><text>US 2003/0021913</text></patcit>.

0098The examples below serve to illustrate the invention without limiting it. In the foregoing and the following, all temperatures are given in degrees Celsius, and all percentages are by weight, unless stated otherwise.

Example 1

0099Polymer <b>8</b> has been synthesised according to Scheme 4 above. <chemistry id="chem0038" num="0038"><img file="EP1510535B1_D0038.tif" /></chemistry>

2,5-Dibromo-3,4-dimethylthieno[2,3-b]thiophene:

0100To a solution of 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid (28.0g, 0.11 mol) in NMP (800 ml) and water (50 ml) was added NBS (44 g, 0.25 mol) portionwise over 30 min. The mixture for stirred for 16 h at RT and poured into water (1 L). The resultant precipitate was filtered and dried under vacuum. Purification by flash chromatography over silica (eluent: petrol) afforded the product as white crystals (27.4 g, 77%). M/Z (326, t, M⁺). NMR gave the expected signals.

2,5-Bis(3-octylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene:

0101To a solution of 2-bromo-3-octylthiophene (4.0 g, 14.5 mmol) in dry THF (20 ml) under nitrogen was added a solution of Rieke zinc (Aldrich, 1.1 g 20 ml of THF, 17 mmol) at -78°C. The solution was allowed to warm to RT and stirred for 16 h. Stirring was stopped and the solution allowed to settle for 2 h. The resultant solution was transferred by cannula into a flask containing 2,5-dibromo-3,4-dimethylthieno[2,3-b]thiophene (1.28 g, 3.9 mmol), degassed THF (50 ml) and [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) chloride (64 mg, 2 mol%) at 0°C. The reaction was warmed to RT over 30 min, and then refluxed for 24 h. The reaction was cooled and quenched with 5% HCL. The resultant mixture was extracted with ethyl acetate (3 x 50 ml), and the combined organics were washed with brine, dried (Na₂SO₄), filtered and concentrated under reduced pressure. The crude product was purified by flash chromatography over silica (eluent: petrol), followed by reverse phase chromatography (eluent: CH₃CN/THF 2:1) to afford the product as a colourless oil (1.56 g, 72%). M/Z 556 (M⁺). Found C, 69.1%, H, 7.6%. Calc. for C₃₂H₄₄S₄ C, 69.0; H 8.0. NMR gave the expected signals.

Poly(2,5-Bis(3-octylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene) (8):

0102To a solution of 2,5-bis(3-octylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene (0.71 g, 1.28 mmol) in dry chloroform (20 ml) was added a solution of anhydrous ferric chloride (1.0 g, 6. 2 mmol) in chloroform (110 ml) dropwise. A constant stream of nitrogen was passed through the solution to remove HCl formed during the reaction. The reaction was stirred for 18 h at 25°C, and then poured into methanol (500 ml). After stirring for 30 min the solution was filtered and washed with water and methanol. The resulting yellow solid was stirred in conc. ammonia solution for 1 h, filtered and dried. The solid was extracted with methanol (soxhlet), iso-hexane (soxhlet) and acetone (soxhlet). The resulting solid was dissolved in chloroform, filtered and precipitated into methanol. The resulting filtrate was dried under vacuum to afford 210 mg of product. GPC (THF) Mn (17,000 g/mol), Mw (20,000 g/mol). λ_max 380 nm (solid film). ¹H NMR gave the expected signals. H Hsuuu00

Example 2

0103Polymer <b>9</b> has been synthesised according to Scheme 4 above. <chemistry id="chem0039" num="0039"><img file="EP1510535B1_D0039.tif" /></chemistry>

2,5-Bis(4-hexylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene:

0104To a solution of 2,5-dibromo-3,4-dimethylthieno[2,3-b]thiophene (3.02 g, 9.28 mmol) and sodium 4-hexylthiophene boronate (5.14 g, 20.4 mmol) in degassed DME (200 ml) was added tetrakis(triphenyl-phosphine)palladium(0) (0.5 g, 5 mol%). The solution was heated to reflux and a saturated soltuion of sodium hyodrogen carbonate (4.2 g, 49 mmol) was added slowly. The reaction was refluxed for 16 h, cooled and diluted with diethyl ether. The layers were separated and the organics washed with 5% HCl, brine, dried (Na₂SO₄), filtered and concentrated under reduced pressure. The crude prodcut was purified by column chromatography over silica (eluent: petrol) to afford the product after recrystallisation from petrol (1.03 g, 22%). M/Z 500 (M⁺). Found C, 66.9.1, H, 6.9, S, 25.3. Calc. for C₂₈H₃₆S₄ C, 67.2; H 7.2, S, 25.6. NMR gave the expected signals.

2,5-Bis(4-hexylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene (9):

0105To a solution of 2,5-bis(4-hexylthiophen-2-yl)-3,4-dimethylthieno[2,3-b]thiophene (0.72 g, 1.45 mmol) in dry chloroform (20 ml) was added a solution of anhydrous ferric chloride (1.0 g, 6. 2 mmol) in chloroform (110 ml) dropwise. A constant stream of nitrogen was passed through the solution to remove HCl formed during the reaction. The reaction was stirred for 18 h at 25°C, and then poured into methanol (500 ml). After stirring for 30 min the solution was filtered and washed with water and methanol. The resulting yellow solid was stirred in conc. ammonia solution for 1 h, filtered and dried. The solid was extracted with methanol (soxhlet), iso-hexane (soxhlet) and acetone (soxhlet). The resulting solid was dissolved in chloroform, filtered and precipitated into methanol. The resulting filtrate was dried under vacuum to afford 250 mg of product. GPC (THF) Mn (9,000 g/mol), Mw (22,000 g/mol). λ_max- 380 nm (solid film). ¹H NMR gave the expected signals.

Example 3

0106Polymer <b>10</b> was synthesised by Stille coupling as described below: <chemistry id="chem0040" num="0040"><img file="EP1510535B1_D0040.tif" /></chemistry>

2-(2,2-Dimethoxyethylsulphanyl)-thiophene:

0107To a solution of 2-thiophenethiol (12.3 g, 106 mmol) in acetone (180 ml), bromoacetaldehyde dimethyl acetal (13.6 ml, 115 mmol) was added, followed by potassium carbonate (21.8g, 158 mmol). The reaction was refluxed for 16 h, cooled, then filtered and concentrated under reduced pressure. The crude product was purified by column chromatography over silica (eluent: petrol:DCM, 2:1) to afford the product as an orange oil (21.0 g, 97%). M/Z 204 (M⁺). Found C, 47.0; H, 5.7; S, 32.3; O, 15.8. Calc. for C₈H₁₂O₂S₂ C, 47.0; H 5.9; S, 31.4; O, 15.7. ¹H NMR (300 MHz, CDCl₃) δ 7.35 (dd, 1 H, J = 1.22 &amp; 5.37 Hz), 7.17 (dd, 1 H, J = 1.22 &amp; 3.58 Hz), 6.97 (dd, 1 H, J = 3.58 &amp; 5.37 Hz), 4.51 (t, 1 H, J = 5.65 Hz), 3.35 (s, 6H), 2.98 (d, 2H, J = 5.65 Hz).

Thieno[2,3-b]thiophene:

0108A solution of 2-(2,2-dimethoxyethylsulphanyl)-thiophene (5.0 g, 24 mmol) in chlorobenzene (50 ml) was added dropwise over 5 minutes to a refluxing solution of 84% polyphosphoric acid (5 ml) in chlorobenzene (100 ml). The reaction mixture was refluxed for 18 h, cooled, poured into water, then extracted with DCM. The organics were washed with water, dried (Na₂SO₄), filtered and concentrated under reduced pressure. The crude product was purified by column chromatography over silica (eluent: petrol) to afford the product as a clear, pale yellow oil (1.53 g, 45%). M/Z 140 (M⁺). Found C, 51.6; H, 2.8; S, 46.4. Calc. for C₆H₄S₂ C, 51.4; H 2.9; S, 45.7. ¹H NMR (300 MHz, CDCl₃) δ 7.35 (d, 2H, J = 5.09 Hz), 7.25 (d, 2H, J = 5.09 Hz). ¹³C NMR (300 MHz, CDCl₃) δ 146.99, 137.28, 128.14, 119.75.

2,5-Bis-trimethylstannyl-thieno[2,3-b]thiophene.

0109A solution of thieno[2,3-b]thiophene (2.81g, 20 mmol) was dissolved in anhydrous THF (100 ml) and cooled to -78°C under nitrogen. A solution of n-butyllithium (17.6 ml of a 2.5M solution in hexanes, 44 mmol) was added dropwise over 15 min, and the resulting solution was allowed to warm to RT and stirred at that temperature for 16 h. The resulting uspension was cooled to -78°C and trimethyltin chloride (10.0g, 50 mmol) was added at once as a solid. The reaction was allowed to warm to RT over 4h and stirred at that temperature for an additional 20 h.

0110The reaction was quenched by the addition of saturated sodium hydrogen carbonate (100 ml). Ethyl acetate (50 ml) was added and the layers separated. The organic layer was washed with sodium carbonate (80 ml of a 2M aqeous solution) and brine (80 ml), dried (sodium sulfate), filtered and concentrated under reduced pressure. The resulting crude product was dry loaded onto a 20g reverse phase silica column and eluted with acetonitrile. The first fraction was collected, concentrated and recrystallised from acetonitrile to afford the product as white flakes (4.15 g, 45%). M/Z cluster centred at 466 (M⁺). Found C, 31.1; H, 4.4; S, 13.8, Calc. for C₁₂H₂₀S₂Sn₂ C, 30.9; H, 4.3; S, 13.8. ¹H NMR (300 MHz, CDCl₃) δ 7.23 (s, 2H), 0.38 (s, 18H). ¹³C NMR (75 MHz, CDCl₃) δ 152.4, 147.7, 142.7, 126.3, -8.2.

5,5'-Dibromo-4,4'-bis(decyl)-2,2'-bithiophene.

01114,4'-Bis(decyl)-2,2'-bithiophene was prepared in analogy to the published procedure (see M. Zagorska and B. Krische <i>Polymer,</i><b>1990,</b> 31, p1379).

0112To a solution of 4,4'-bis(decyl)-2,2'-bithiophene (6.60 g, 14.8 mmol) in chloroform (100 ml) and glacial acetic acid (100 ml) at 5°C in the dark was added N-bromosuccinimde (5.40 g, 30 mmol) portionwise over 1 h. The resulting solution was warmed to 20°C and stirred for a further 16h. The solvent was removed under reduced pressure and the residue suspended in MTBE (200 ml). Filtration of the solution removed succinimde byproduct. The filtrate was washed with 5% sodium carbonate (100 ml), water (100 ml) and brine (100 ml), dried (sodium sulfate), filtered and concentrated under reduced pressure. The resulting crude product was further purified by reverse phase column chromatography over RP18 silica (23 g) eluting with acetonitrile/THF 2:1. A final recrystallisation from ethyl acetate afforded the product (2.94 g, 33%). HRMS 602.1248 (calc. for C₂₈H₄₄S₂Br⁷⁹₂ 602.1251 ). ¹H NMR (300 MHz, CDCl₃) δ 6.77 (s, 2H), 2.70 (t, 4H), 1.57 (quint, 4H), 1.28 (m, 28H), 0.88 (t, 6H). ¹³C NMR (75 MHz, CDCl₃) δ 143.0, 136.1, 124.5, 107.9, 31.9, 29.62, 29.57, 29.40, 29.35, 29.2, 22.7, 14.2.

Poly(2,5-bis(3-decylthiophen-2-yl)thieno[2,3-b]thiophene) (10):

0113A 10 ml glass vial was charged with a stirrer bar, 5,5'-dibromo-4,4'-didecylbithiophene (182 mg, 0.3 mmol), 2,5-bis(trimethylstannyl)-thieno[2,3-b]thiophene (140 mg, 0.3 mmol), tris(dibenzylideneacetone)dipalladium (0) (5.5 mg, 2 mol %), tri(o-tolyl)phosphine (14.6 mg, 16 mol %) and chlorobenzene (4.5 ml). The glass vial was purged with nitrogen and securely sealed. The glass vial was placed into a microwave reactor (Emrys Creator, Personal Chemistry Ltd) and heated to 200°C. A temperature ramp was used such that the vial was heated with stirring at 140°C for 60 seconds, then 160°C for 60s, 180°C for 60 s, and finally 200°C for 10 minutes. Elapsed time was only calculated once the temperature had been reached. After cooling to RT, the reaction mixture was precipitated into a mixture of methanol (50 ml) and concentrated hydrochloric acid (2 ml) and and stirred for 16 h at 20°C. The precipitate was filtered and extracted with methanol (soxhlet) and acetone (soxhlet) for 12 h each. Finally the polymer was dissolved in warm chloroform, filtered and precipitated in petrol. The polymer was collected by centrifugation and dried under vacuum to afford the 105 mg of product. GPC (CHCl₃) Mn (15,000 g/mol), Mw (32,000 g/mol). λ_max465 nm (solid film). ¹H NMR (300 MHz, CDCl3, 50°C) δ 7.22 (s, 2H), 7.03 (s, 2H), 2.77 (t, 4H), 1.69 (quint, 4H), 1.4-1.20 (m, 28H), 0.88 (t, 6H).

Example 4

0114Polymer <b>11</b> was synthesised by Stille coupling as described below: <chemistry id="chem0041" num="0041"><img file="EP1510535B1_D0041.tif" /></chemistry><chemistry id="chem0042" num="0042"><img file="EP1510535B1_D0042.tif" /></chemistry>

3,6-Dioctylthieno[3,2-b]thiophene:

0115A 20 ml glass vial was charged with a stirrer bar, 3,6-dibromo-thieno[3,2-b]thiophene (see Fuller, L.S.; Iddon, B.; Smith, K.A. <i>J. Perkin Trans. 1</i>, <b>1997</b>, p3465) (1.0 g, 3.35 mmol) and (1,1'-bis(diphenylphosphino)ferrocene)palladium (II) chloride (10 mg, 0.014 mmol). The glass vial was securely sealed and then purged with nitrogen. THF (2 ml) and octylzinc bromide (16.8 mL of a 0.5M solution in THF) were added, and the reaction stirred for 3 min at 25°C. The mixture was heated in a microwave reactor (Emrys Creator, Personal Chemistry Ltd) at 150°C for 7 min. The reaction was cooled, diluted with MTBE (20 ml) and washed with 5% HCl (10 ml), water (3 x 10 ml), brine (10 m), dried (sodium sulfate), filtered and concentrated under reduced pressure. The crude material was further purified by filtration over silica (eluent: petrol), and the resulting waxy solid was recrystallised from ethanol to afford the product as a pale yellow solid (0.65 g, 54%). M/Z 364 (M⁺). Found C, 72.3; H, 9.7, Calc. for C₂₂H₃₆S₂ C, 72.5; H, 9.9. ¹H NMR (300 MHz, CDCl₃) δ 8.95 (2H, s), 2.70 (4H, t), 1.74 (4H, quint), 1.31 (20H, m), 0.88 (6H, t). ¹³C NMR (75 MHz, CDCl₃) δ 139.3, 135.5, 120.8, 31.9, 29.8, 29.42, 29.37, 29.2, 28.8, 22.7, 14.1.

2,5-Dibromo-3,6-dioctylthieno[3,2-b]thiophene:

0116To a solution of 3,6-dioctylthieno[3,2-b]thiophene (2.0g, 5.5 mmol) in glacial acetic acid (50 ml) and chloroform (50 ml) at 5°C was added N-bromosuccinimide (1.95 g, 11 mmol) portionwise over 1 h. The solution was stirred for a further 24 h at 20°C. The solvent was removed under reduced pressure , and the residue suspended in MTBE (100 ml) and filtered to remove succimide byproduct. The organic filtrate was washed with water (50 ml), 5% Na2CO3 (50 ml) and water (50 ml), dried (sodium sulfate), filtered and concentrated under reduced pressure. The residue was further purified by filtration thorugh silica (eluent: petrol) to afford a yellow oil that crystallised upon standing (2.37 g, 83%). HRMS 520.0472 (calc. for C₂₂H₃₄S₂Br⁷⁹₂ 520.0469). ¹H NMR (300 MHz, CDCl₃) δ 2.66 (4H, t), 1.65 (4H, quint), 1.29 (20H, m), 0.87 (6H, t). ). ¹³C NMR (75 MHz, CDCl₃) δ 136.1, 134.4, 109.4, 31.9, 29.32, 29.27, 29.19, 28.1, 22.7, 14.1.

Poly(3,6-dioctylthieno[3,2-b]thiophene-co-thieno[2,3-b]thiophene) (11):

0117A 10 ml glass vial was charged with a stirrer bar, 2,5-dibromo-3,6-dioctylthieno[3,2-b]thiophene (157 mg, 0.3 mmol), 2,5-bis(trimethylstannyl)-thieno[2,3-b]thiophene (140 mg, 0.3 mmol), tris(dibenzylideneacetone)dipalladium (0) (5.5 mg, 2 mol %), tri(o-tolyl)phosphine (14.6 mg, 16 mol %) and chlorobenzene (6 ml). The glass vial was purged with nitrogen and securely sealed. The glass vial was placed into a microwave reactor (Emrys Creator, Personal Chemistry Ltd) and heated to 200°C. A temperature ramp was used such that the vial was heated with stirring at 140°C for 60 seconds, then 160°C for 60s, 180°C for 60 s, and finally 200°C for 10 minutes. Elapsed time was only calculated once the temperature had been reached. After cooling to RT, the reaction mixture was precipitated into a mixture of methanol (50 ml) and concentrated hydrochloric acid (2 ml) and and stirred for 16 h at 20°C. The precipitate was filtered and extracted with methanol (soxhlet) and acetone (soxhlet) for 12 h each. Finally the polymer was dissolved in hot dichlorobenzene, filtered and precipitated in petrol. The polymer was collected by filtration and dried under vacuum to afford the 95 mg of product. GPC (CHCl₃) Mn (6,400 g/mol), Mw (9,400 g/mol). λ_max 414 nm (solid film).

Example 5

0118Polymer <b>12</b> was prepared by analogy to example 4. <chemistry id="chem0043" num="0043"><img file="EP1510535B1_D0043.tif" /></chemistry>

Poly(3,6-didodecyllthieno[3,2-b]thiophene-<i>co</i>-thieno[2,3-b]thiophene) (12):

0119A 10 ml glass vial was charged with a stirrer bar, 2,5-dibromo-3,6-didodecylthieno[3,2-b]thiophene (127 mg, 0.2 mmol), 2,5-bis(trimethylstannyl)-thieno[2,3-b]thiophene (93 mg, 0.2 mmol), tris(dibenzylideneacetone)dipalladium (0) (3.7 mg, 2 mol %), tri(o-tolyl)phosphine (6.0 mg, 8 mol %), lithium chloride (8.5 mg, 0.2 mmol) and chlorobenzene (5 ml). The glass vial was purged with nitrogen and securely sealed. The glass vial was placed into a microwave reactor (Emrys Creator, Personal Chemistry Ltd) and heated to 200°C. A temperature ramp was used such that the vial was heated with stirring at 140°C for 60 seconds, then 160°C for 60s, 180°C for 60 s, and finally 200°C for 10 minutes. Elapsed time was only calculated once the temperature had been reached. After cooling to RT, the reaction mixture was precipitated into a mixture of methanol (50 ml) and concentrated hydrochloric acid (2 ml) and and stirred for 4 h at 20°C. The precipitate was filtered and extracted with acetone (soxhlet) and petrol (soxhlet) for 12 h each. Finally the polymer was dissolved in hot dichlorobenzene, filtered and precipitated in petrol. The polymer was collected by filtration and dried under vacuum to afford the 78 mg of product. GPC (CHCl₃) Mn (14,000 g/mol), Mw (22,0 00 g/mol). λ_max 414 nm (solid film).

Example 6

0120Polymer <b>13</b> has been synthesised according to Scheme 8 above. <chemistry id="chem0044" num="0044"><img file="EP1510535B1_D0044.tif" /></chemistry>

2,5-Diiodo-thieno[2,3-b]thiophene:

0121A solution of thieno[2,3-b]thiophene (1.0 g, 7.1 mmol) in anhydrous tetrahydrofuran (40 ml), was cooled under nitrogen to -78°C, before adding n-butyl lithium, 2.5M in hexanes (6.8 ml) dropwise, and stirring at room temperature for 3 h. The reaction mixture was then cooled to -60°C, before adding iodine (3.6 g, 14 mmol), then stirring at room temperature for 18 h, with the exclusion of light. The reaction mixture was poured into water, extracted with DCM, washed with water, dried (Na₂SO₄), filtered and concentrated under reduced pressure. The crude product was purified by column chromatography over silica (eluent: petrol) to afford the product after recrystallisation from hot IMS as colourless platelet crystals (1.77 g, 63%). M/Z 392 (M⁺). Found C, 18.5; H, 1.1; I, 65.0; S, 15.6. Calc. for C₆H₂I₂S₂ C, 18.4; H, 0.5; I, 64.7; S, 16.4. ¹H NMR (300 MHz, CDCl₃) δ 7.34 (s, 2H).

Poly(3-hexylthiophene-<i>co</i>thieno[2,3-b]thiophene):

0122To a solution of 2,5-dibromo-3-hexylthiophene (1.78 g, 5.45 mmol) and 2,5-diiodo-thieno[2,3-b]thiophene (0.24 g, 0.61 mmol) in anhydrous THF (28 ml) at 0°C under nitrogen was added isopropylmagnesium chloride (3.3 ml of a 2.0M solution in THF, 6.6 mmol). The resulting solution was allowed to warm to room temperature and stirred for 4 h. [1,3-bis(diphenylphosphino)propane]-dichloronickel(II) (16 mg, 0.03 mmol) was added at once as a solid and the resulting mixture for stirred for 72 h at room temperature. The reaction was poured into methanol (180 ml) containing 37% HCl (20 ml) and stirred for 30 min. The precipitate was filtered and extracted successively with methanol (soxhlet), acetone (soxhlet) and iso-hexane (soxhlet). Finally the polymer was dissolved in chloroform and precipitated into methanol. The resulting precipitate was dried under vacuum to afform the product ( ). GPC (CHCl₃) Mn (13,000 g/mol), Mw (40,000 g/mol). λ_max 462 nm (solid film).

Example 7

0123Monomer <b>15</b> has been synthesised according to the following scheme: <chemistry id="chem0045" num="0045"><img file="EP1510535B1_D0045.tif" /></chemistry>

(6-[2,2']Bithiophenyl-5-yl-hexyloxy)-tert-butyl-dimethylsilane:

0124To a stirred solution of 2,2'-bithiophene (10.0 g, 60.24 mmol) in dry THF (150 ml) was added <i>n</i>-butyllithium (2.5 M in hexanes, 20.0 ml, 50.0 mmol) dropwise at -78 °C under nitrogen. After complete addition, the mixture was allowed to warm to room temperature, with stirring, over 2 h, followed by the addition of 6-bromohexyloxy-<i>tert</i>-butyldimethylsilane (14.75 g, 50.0 mmol). The resultant mixture was stirred overnight at room temperature. The reaction was quenched with sat. aq. ammonium chloride, and the reaction mixture was extracted with ethyl acetate (3 × 70 ml). The combined organic extracts were washed with water, brine, and dried over magnesium sulphate. The solvent was removed under reduced pressure and the residue was purified by column chromatography (silica gel, petroleum/ethyl acetate from 100: 0 to 20:1), to afford the product as a pale green oil (15.07 g, 79 %). ¹H NMR (300 MHz, CDCl₃): δ (ppm) 7.08 (m, 1 H, Ar-H), 7.03 (m, 1 H, Ar-H), 6.92 (m, 2H, Ar-H), 6.61 (d, <i>J</i> = 3.6 Hz, 1 H, Ar-H), 3.55 (t, <i>J</i> = 6.2 Hz, 2H, OCH₂), 3.34 (t, J = 6.8 Hz, 2H, ArCH₂), 1.25-1.85 (m, 8H, CH₂), 0.86 (s, 9H, CH₃), 0.01 (s, 6H, CH₃); ¹³C NMR (75 MHz, CDCl₃): δ (ppm) 145.1 (quat.), 138.0 (quat.), 134.8 (quat.), 127.6 (CH), 124.7 (CH), 123.7 (CH), 123.4 (CH), 122.9 (CH), 63.0 (OCH₂), 33.8 (CH₂), 32.9 (CH₂), 32.7 (CH₂), 28.0 (CH₂), 26.0 (CH₃) 25.1 (CH₂), 18.4 (quat.), -5.2 (CH₃); MS (<i>m</i>/<i>e</i>): 380 (M⁺, 27%), 323 (63), 179 (100), 75 (37).

2-{5'-[6-(tert-Butyl-dimethyl-silanyloxy)-hexyl]-[2,2']bithiophenyl-5-yl}-4,4,5,5-tetramethyl-[1,3,2}dioxaborolane:

0125To an ice-cooled solution of (6-[2,2']bithiophenyl-5-yl-hexyloxy)-tert-butyl-dimethylsilane (10 g, 19.76 mmol) in anhydrous THF (150 ml) was added dropwise a solution of n-butyllithium (2.5 M in hexanes, 7.91 ml, 19.76 mmol) under nitrogen, with stirring. After 2 h, pinacol boronate (4.04 g, 21.72 mmol) was added. The ice bath was removed, and the resultant mixture was stirred overnight at room temperature. The reaction was quenched with the addition of saturated aqueous NH₄Cl and the mixture extracted with ethyl acetate (3 × 70 ml). The combined organic extracts were washed with brine, dried over magnesium sulphate, and evaporated under reduced pressure. The residue was purified by column chromatography on silica, eluting with petroleum ether / ethyl (9:1), to give the product as a blue oil (9.52 g, 72 %). ¹H NMR (300 MHz, CDCl₃): δ (ppm) 7.46 (d, <i>J</i> = 3.6 Hz, 1 H, Ar-H), 7.10 (d, <i>J</i> = 3.6 Hz, 1 H, Ar-H), 6.99 (d, J = 3.4 Hz, 1 H, Ar-H), 6.62 (d, <i>J</i> = 3.4 Hz, 1 H, Ar-H), 3.56 (t, J = 6.4 Hz, 2H, OCH₂), 2.73 (t, J = 7.4 Hz, 2H, ArCH₂), 1.21-1.70 (m, 20H, CH₂ and CH₃), 0.86 (s, 9H, CH₃), 0.01 (s, 6H, CH₃); ¹³C NMR (75 MHz, CDCl₃): δ (ppm) 145.9 (2 × quat.), 144.8 (quat.), 138.0 (CH.), 134.7 (quat.), 125.0 (CH), 124.2 (CH), 124.1 (CH), 84.1 (quat.), 63.2 (OCH₂), 32.8 (CH₂), 31.6 (CH₂), 30.2 (CH₂), 28.9 (CH₂), 26.0 (CH₃) 25.6 (CH₂), 24.8 (CH₃), 18.4 (quat.), -5.2 (CH₃); MS (m/e): 506 (M⁺, 32 %), 331 (31), 305 (31), 279 (100), 261 (32), 205 (51), 83 (71).

2,5-Bis-{5'-[6-(tert-butyldimethylsilanyloxy)-hexyl]-[2,2']bithiophenyl-5-yl}-thieno[2,3-b]thiophene:

0126Tetrakis(triphenylphosphine)palladium(0.05 g) was added to a solution of 2,5-diiodothioeno[2,3-b]thiophene (0.10 g, 0.26 mmol) in dry THF, with stirring, under nitrogen. After 20 min, 2-{5'-[6-(tert-butyldimethylsilanyloxy)hexyl]-[2,2']bithiophenyl-5-yl}-4,4,5,5-tetramethyl[1,3,2]dioxaborolane (0.41 g, 0.80 mmol) and a solution of potassium carbonate (0.22 g,1.60 mmol) in water (5 ml) was added. The resultant mixture was heated at reflux for 1.5 h. After cooling, water (50 ml) was added and the precipitate filtered off, washed with water and diethyl ether, to give a yellow solid (0.20 g, 87 %). λ_MAX (CHCl₃) 395 nm; ¹H NMR (300 MHz, CDCl₃): δ (ppm) 7.21 (s, 2H, Ar-H), 7.06 (d, <i>J</i> = 3.8 Hz, 2H, Ar-H), 6.99 (m, 4H, Ar-H), 6.68 (d, <i>J</i> = 3.6 Hz, 2H, Ar-H); 3.61 (t, <i>J</i> = 6.4 Hz, 4H, OCH₂), 2.80 (t, <i>J</i> = 7.3 Hz 4H, ArCH₂), 1.31-1.68 (m, 16H, CH₂), 0.90 (s, 18H, CH₃); 0.05 (s, 12H, CH₃). ¹³C NMR (75 MHz, CDCl₃): δ (ppm) 146.2, 145.7, 139.9, 137.3, 135.5, 135.0, 134.4, 124.8, 124.5, 123.6, 123.5, 116.0, 63.1, 32.7, 31.5, 30.1, 28.8, 25.9, 25.5, 18.3, -4.3.

Use Example A

0127A comparison of the optical properties of polymers <b>8, 10, 11, &amp; 13</b> according to the examples 1, 3, 4 and 6 with the fully conjugated thiophene co-polymer <b>14</b> of prior art was made. <chemistry id="chem0046" num="0046"><img file="EP1510535B1_D0046.tif" /></chemistry>

0128<figref idref="f0001"><b>Figures 1</b></figref> and <figref idref="f0002"><b>2</b></figref> show the UV spectra of polymer films cast from solution of polymers <b>8, 10, 11 &amp; 13</b> (<figref idref="f0001">Figure 1</figref>) and <b>14</b> (<figref idref="f0002">Figure 2</figref>). It is immediately apparent that the maximum absorbance of the thieno[2,3-b]thiophene containing polymers <b>8, 10, 11, 13</b> are all blue shifted in comparison to the thiophene only polymer 14 (up to 160 nm). Furthermore, polymer <b>8</b> has a blue solid-state photoluminescence in comparison to orange for polymer <b>10</b>.

Use Example B - Transistor Fabrication and Measurement

0129Thin-film organic field-effect transistors (OFETs) were fabricated on highly doped silicon substrates with thermally grown silicon oxide (SiO₂) insulating layer, where the substrate served as a common gate electrode. Transistor source-drain gold electrodes were photolithographically defined on the SiO₂ layer. Prior to organic semiconductor deposition, FET substrates were treated with a silylating agent hexamethyldisilazane (HMDS). Thin semiconductor films were then deposited by spin-coating polymer solutions in chloroform or xylene (0.4-1 wt%) on FET substrates. The electrical characterization of the transistor devices, was carried out under ambient atmosphere using computer controlled Agilent 4155C Semiconductor Parameter Analyser.

0130Transistor characteristics for examples <b>10</b> and <b>12</b> were measured on films prepared by spin coating. The results are shown in table 1. The films were heated to 100°C for 10 min under nitrogen to remove residual solvent, and then cooled to room temperature to measure the transistor characteristics.

0131<figref idref="f0003"><b>Figure 3a</b></figref> and <figref idref="f0004"><b>3b</b></figref> show the transfer and output characteristics for compound 10 of example 3. Depicted is the current (I) - voltage (V) characteristics in a transistor device with 10 micron channel length and 20,000 micron channel width. <figref idref="f0003"><b>Figure 3a</b></figref> shows the transfer curves. The transistor gate voltage (V_g) is varied between 20 and -60 volts for two different setting of Source -Drain voltage (V_sd). The transistor Source -Drain current I_sd is plotted versus V_g for V_sd= -5 (dotted line) and -60 V (solid line), respectively. <figref idref="f0004"><b>Figure 3b</b></figref> shows the output curves. The Source -Drain voltage (V_sd) is varied between 0 and -60 volts with a different bias voltage applied to the gate electrode (V_g). The transistor Source -Drain current (I_sd) is plotted versus V_sd for V_g= 0, -15, -30, -45 and -60 V, respectively.

0132The devices showed typical p-type behaviour with good current modulation, and well-defined linear and saturation regimes. Field effect mobility was calculated in the saturation regime (V_d > (V_g-V₀)) using equation (1)<maths id="math0001" num="(1)"><math display="block"><msub><mfenced><mfrac><mrow><mi mathvariant="normal">d</mi><mo>⁢</mo><msup><msub><mi mathvariant="normal">I</mi><mi mathvariant="normal">d</mi></msub><mi>sat</mi></msup></mrow><mrow><mi mathvariant="normal">d</mi><mo>⁢</mo><msub><mi mathvariant="normal">V</mi><mi mathvariant="normal">g</mi></msub></mrow></mfrac></mfenced><msub><mi mathvariant="normal">V</mi><mi mathvariant="normal">d</mi></msub></msub><mo mathvariant="normal">=</mo><mfrac><mrow><mi mathvariant="normal">W</mi><mo>⁢</mo><msub><mi mathvariant="normal">C</mi><mi mathvariant="normal">i</mi></msub></mrow><mi mathvariant="normal">L</mi></mfrac><mo>⁢</mo><msup><mi mathvariant="normal">μ</mi><mi>sat</mi></msup><mo>⁢</mo><mfenced><msub><mi mathvariant="normal">V</mi><mi mathvariant="normal">g</mi></msub><mo mathvariant="normal">-</mo><msub><mi mathvariant="normal">V</mi><mn mathvariant="normal">0</mn></msub></mfenced></math><img file="EP1510535B1_D0047.tif" /></maths> wherein W is the channel width, L the channel length, C_i the capacitance of insulating layer, V_g the gate voltage, V_d the drain voltage, I_d the drain current, V₀ the turn-on voltage and µ^sat is the saturated charge carrier mobility. The turn-on voltage (V₀) was determined as the onset of source-drain current (<figref idref="f0003 f0004"><b>Figure 3</b></figref>).

0133Materials <b>10</b> and <b>12</b> demonstrated good air stability, as exemplified by the high on/off ratios for measurements in air (table 1). The device characteristics showed little change after testing following storage in air. <tables id="tabl0001" num="0001"><table frame="none"><title>Table 1</title><tgroup cols="3" rowsep="0"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="39mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><thead valign="top"><row rowsep="1"><entry colsep="0">Material</entry><entry colsep="0">Initial Saturated Mobility</entry><entry colsep="0">On/off ratio</entry></row></thead><tbody><row><entry colsep="0"><b>10</b></entry><entry colsep="0">1.7 x 10^-2 cm²/vs</entry><entry colsep="0">1 x10⁶</entry></row><row rowsep="1"><entry colsep="0"><b>12</b></entry><entry colsep="0">3 x 10^-3 cm²/vs</entry><entry colsep="0">2 x 10⁶</entry></row></tbody></tgroup></table></tables>