JP5138422B2 - Polymer containing benzothieno [3,2-b] benzothiophene structure - Google Patents

Description

  The present invention relates to a polymer having a benzothieno [3,2-b] benzothiophene group, which is useful as a material for various organic electronics such as a photoelectric conversion element, a thin film transistor element, and a light emitting element.

  In recent years, research and development of organic thin film transistors using organic semiconductor materials has been active. Organic semiconductor materials can be easily formed into thin films by a simple process using a wet process such as a printing method, spin coating method, etc., and the temperature of the manufacturing process can be lowered as compared with a thin film transistor using a conventional inorganic semiconductor material. There is an advantage. This enables formation on plastic substrates with generally low heat resistance, which can reduce the weight and cost of electronic devices such as displays, and is expected to be used in a variety of ways, including applications that take advantage of the flexibility of plastic substrates. it can.

  Up to now, acene-based materials such as pentacene have been reported as such organic semiconductor materials (see Patent Document 1). Organic thin-film transistors using pentacene as an organic semiconductor layer have been reported to have a relatively high mobility, but these acene-based materials have extremely low solubility in general-purpose solvents. For this reason, in order to make it into a thin film as an organic semiconductor layer in an organic thin film transistor, it is necessary to go through a vacuum deposition process. Therefore, it does not meet the expectation for an organic semiconductor material that a thin film is formed by a simple process such as a coating method or a printing method as described above.

  In the case of polymer materials, PPV (poly-p-phenylene-vinylene) has been mainly studied so far. Since this material has a rigid main chain, it has a difficulty in poor solubility. For this reason, poly (3-alkylthiophene) (see Non-Patent Document 1) or a copolymer of dialkylfluorene and bithiophene (see Non-Patent Document 2) has been proposed as a polymer material. Since these polymer organic semiconductor materials have a certain degree of solubility due to the introduction of alkyl groups, they can be thinned by coating or printing without going through a vacuum deposition process.

However, since these high molecular organic semiconductor materials achieve high mobility in a state where the molecules are aligned, the alignment state differs depending on the solvent type, coating method, etc. when forming the thin film. A transistor formed as a thin film has problems in that the transistor characteristics vary and the reproducibility of the characteristics is poor, and the fact is that it is poor although it has solubility because it has a rigid main chain. It was.
Poly (3-alkylthiophene) has high planarity due to its structure. Therefore, while exhibiting a relatively low ionization potential, it can be easily oxidized in air, which can lead to degradation of device characteristics.

  However, benzothieno [3,2-b] benzothiophene or a derivative thereof having such a structure is a condensed polycyclic aromatic containing two sulfur atoms in the molecule, and its molecular structure is completely planar. In addition, compared with pentacene, which is a similar condensed polycyclic aromatic, it has a high ionization potential and is stable against oxidation, and therefore, its potential for application to organic semiconductors is considered.

For example, 2,7-diphenylbenzothieno [3,2-b] benzothiophene represented by the following formula (1), which is a derivative of benzothieno [3,2-b] benzothiophene (Patent Document 2 and Non-Patent Document 3) reference), by depositing on a substrate treated with octadecyl trichlorosilane, a mobility comparable to pentacene showed about 2.0cm 2 / V · ^s, and also long-term stability under atmospheric Yes doing. Similarly, 2,7-dialkylbenzothieno [3,2-b] benzothiophene (see Non-Patent Document 4) represented by the following formula (2) which is the above derivative has liquid crystallinity, and Since it has high solubility, it can be applied by spin coating, casting, etc., and the mobility comparable to that of pentacene is shown by the heat treatment at a relatively low temperature, which is about 2.0 cm ² / V · s. ing.

  However, the former derivative [2,7-diphenylbenzothieno [3,2-b] benzothiophene represented by the above formula (1)] needs to go through a vacuum deposition process, which means that a thin film is formed by a simple process. The latter derivative [2,7-dialkylbenzothieno [3,2-b] benzothiophene represented by the above formula (2)] has a liquid crystal temperature (temperature indicating a liquid crystal phase) of about 100 ° C. Since the film structure can be changed by heat treatment, there is a problem in process adaptability in manufacturing an organic semiconductor device.

  For the above-mentioned reasons, the above-mentioned known derivatives have a problem in process adaptability, but in such a polymer material having a benzothieno [3,2-b] benzothiophene skeleton, which is a similar derivative, It is expected to discover structures with physical properties that are excellent in solubility and oxidation stability. However, among the conventional derivatives having a benzothieno [3,2-b] benzothiophene skeleton, a polymer having a sufficient molecular weight suitable for the coating process has not yet been reported to the extent that the present inventors can know. .

JP-A-5-55568 WO2006 / 0777888 Appl. Phys. Lett. , 69 (26), 4108 (1996) Science, 290, 2123 (2000) J. et al. Am. Chem. Soc. 128, 12604 (2006) Kazuo Sasamiya et al., Poster presentation materials for the 54th Joint Physics Related Conference on Applied Physics in FY 20007 “Solution Process Organic FETs Using Low Molecular Compounds”

  The present invention has been made in view of the above problems of the prior art, is easy to synthesize, has high solubility, film-forming property, and oxidation stability, and is useful as a polymer material for an active layer of an organic thin film transistor. It is an object to provide a novel polymer.

As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by a polymer having the following structure, and have completed the present invention.
That is, this invention consists of the following.
(1) The invention according to claim 1 is a polymer containing a benzothieno [3,2-b] benzothiophene structure characterized by having a repeating unit represented by the following general formula (I).

(In the formula, Ar is a divalent group which may have a substituent, and the divalent group is any one of thiophene, bithiophene, terthiophene, quarterthiophene, phenyl, biphenyl, terphenyl and quarterphenyl. A group selected from more.)

(2) The invention according to claim 2 is the polymer according to claim 1, wherein when Ar has a substituent, the substituent is aliphatic or alicyclic alkyl having 1 to 22 carbon atoms. Group, halogen, aliphatic or alicyclic alkyl group having 1 to 25 carbon atoms, alkoxy group having 1 to 25 carbon atoms, thioalkoxy group having 1 to 25 carbon atoms, nitro group, cyano group, sulfone group And a group selected from sulfoxide groups, wherein the number of substituents may be plural, and the plural substituents may be the same or different.

  According to the present invention, a single amount of benzothieno [3,2-b] benzothiophene, which is capable of forming a thin film by a simple process such as a coating method or a printing method, and has excellent solubility and oxidation stability, and phenylene or thiophene. The polymer which consists of a body and a multimer can be provided.

Hereinafter, the (π-conjugated) polymer of the present invention will be described in more detail.
Benzothieno [3,2-b] benzothiophene has a highly developed π-conjugated system and a high planar structure, and has been proposed as an organic semiconductor material as described above. Specifically, it is shown in Non-Patent Documents 3 and 4. However, when it does not have a soluble substituent, film formation under conditions under high vacuum is essential. In the case of a derivative to which a soluble group such as alkyl is added, although solubility is obtained, the melting point is lowered, and there is a concern that the film structure may be disturbed due to heat treatment or the like during device fabrication.
Therefore, the present inventors have focused on obtaining a polymer obtained by copolymerizing benzothieno [3,2-b] benzothiophene and arylene having a soluble group or heteroarylene, and solved the above problems.

That is, the polymer of the present invention has a repeating unit of a unit having an aromatic hydrocarbon or thiophene divalent group (arylene group or heteroarylene group) on divalent benzothieno [3,2-b] benzothiophene. It is a conjugated polymer and has a repeating unit represented by the following general formula (I).

  In the above general formula (I), Ar is a divalent group which may have a substituent, and is selected from any of thiophene, bithiophene, terthiophene, quarterthiophene, phenyl, biphenyl, terphenyl and quarterphenyl. When it has a substituent (divalent π electron conjugated group), the number of substituents may be plural, and the plural substituents may be the same or different. In addition, as the substituent, an aliphatic or alicyclic alkyl group having 1 to 22 carbon atoms, a halogen, an aliphatic or alicyclic alkyl group having 1 to 25 carbon atoms, or a C 1-25 alkyl group. Examples thereof include a group selected from an alkoxy group, a thioalkoxy group having 1 to 25 carbon atoms, a nitro group, a cyano group, a sulfone group, and a sulfoxide group.

  The novel π-conjugated polymer of the present invention introduces a molecule having a solubility group typified by an alkyl group to ensure solubility in a general (general purpose) organic solvent, while maintaining crystallinity / liquid crystallinity / An organic film having a regular aggregated state such as orientation can be formed more advantageously. In such a highly regular state, higher mobility than in the amorphous state can be expected.

As a method for producing the π-conjugated polymer of the present invention represented by the general formula (I), a method of polymerizing by a Suzuki coupling reaction (Suzuki coupling reaction), a method of polymerizing by a Stille coupling reaction (coupling reaction), Ni ( 0) Complex: a method such as a Yamamoto coupling reaction, which is polymerized by a nickel zero-valent complex (hereinafter sometimes referred to as “Ni (0)” or “nickel (0)”), FeCl ₃ Known methods such as a method of polymerizing with an oxidizing agent such as the above, or a method of electrochemically oxidatively polymerizing can be used. Among these, the method of polymerizing by Suzuki coupling reaction, the method of polymerizing by Stille coupling reaction, and the method of polymerizing by nickel zero-valent complex are preferable because they are simple and easy to control the structure.

An example of synthesizing a polymerization method using the Suzuki coupling reaction is given below.
A benzothieno [3,2-b] benzothiophene derivative (halogenated benzothieno [3,2-b] benzothiophene derivative) represented by the following general formula (II) and a boronic acid represented by the following general formula (III) The π-conjugated polymer of the present invention represented by the general formula (I) is produced by reacting the derivative with a base in the presence of a palladium catalyst.

(In the above formula (II), X represents a chlorine atom, a bromine atom or an iodine atom.)
Y-Ar-Y (III)
(In the above formula (III), Ar represents an arylene group or heteroarylene group which may have a substituent, and Y represents a boronic acid or an ester thereof.)

  In the polymerization method using the Suzuki coupling reaction, the halogen atom in the halogenated benzothieno [3,2-b] benzothiophene derivative represented by the general formula (II) is preferably iodine or bromine from the viewpoint of reactivity.

  As the boronic acid derivative represented by the general formula (III), aryl boronic acid or a boronic acid ester synthesized from a halogenated derivative using bis (pinacolato) diboron which is thermally stable and can be easily handled in air is used. It may be used.

Various catalysts such as Pd (PPh ₃ ) ₄ , PdCl ₂ (PPh ₃ ) ₂ , Pd (OAc) ₂ , and PdCl ₂ can be used as the palladium catalyst, but most commonly used is Pd (PPh ₃ ). ₄ is used.

A base is absolutely necessary for the Suzuki coupling reaction, but relatively weak bases such as Na ₂ CO ₃ , NaHCO ₃ give good results. When affected by steric hindrance or the like, a strong base such as Ba (OH) ₂ , K ₃ PO ₄ , or NaOH is effective. In addition, caustic potash, metal alkoxide, etc., for example, potassium t-butoxide, sodium t-butoxide, lithium t-butoxide, potassium 2-methyl-2-butoxide, sodium 2-methyl-2-butoxide, sodium methoxide, sodium ethoxide, Potassium ethoxide, potassium methoxide, etc. can also be used. An organic base such as triethylamine can also be used.

  Reaction solvents include water, methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether and other cyclic ethers such as dioxane and tetrahydrofuran. Benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2- Examples include imidazolidinone.

An example of a polymerization method using Stille coupling reaction is also given. In this method, the halogenated benzothieno [3,2-b] benzothiophene derivative represented by the above general formula (II) and the organotin derivative represented by the following general formula (IV) are present in the presence of a palladium catalyst. By reacting with π, a π-conjugated polymer represented by the above general formula (I) is produced. As the palladium catalyst, the same catalyst as described in the Suzuki coupling reaction is used.
Z-Ar-Z (IV)
(In the formula, Ar has the same meaning as Ar in the formula (III), and Z represents an organotin functional group.)
As the organotin derivative represented by the general formula (IV), a derivative having an alkyltin group such as a SnMe ₃ group or a SnBu ₃ group can be used.

In the Yamamoto coupling method in which polymerization is performed with a Ni (O) complex, as the organotin derivative represented by the general formula (IV), a derivative having an alkyltin group such as SnMe ₃ group or SnBu ₃ group can be used. . In the case of using a zero-valent nickel complex such as this Yamamoto reaction, preferred substituents involved in polymerization include a halogen atom, an alkyl sulfonate group, an aryl sulfonate group, or an aryl alkyl sulfonate group.

  Examples of the zero-valent nickel complex used in the Yamamoto reaction include bis (1,5-cyclooctadiene) nickel (0), (ethylene) bis (triphenylphosphine) nickel (0), tetrakis (triphenylphosphine) nickel, etc. And bis (1,5-cyclooctadiene) nickel (0) is preferred.

  The reaction temperature of the polymerization reaction by each of the above coupling reactions is appropriately set depending on the reactivity of the monomer used and the reaction solvent, but it is preferable to keep it below the boiling point of the solvent.

  The reaction time in the polymerization reaction by each of the above coupling reactions can be appropriately set in terms of the reactivity of the monomer used or the molecular weight of the desired polymer, and is preferably 2 to 72 hours. -48 hours is more preferred.

  In addition, in the polymerization operation by each coupling reaction described above, a molecular weight regulator or a sealing agent for sealing the end of the polymer as a terminal modifying group is added to adjust the molecular weight during or after the reaction. It is also possible to add it at the start of the reaction. Therefore, a substituent based on a terminator may be bonded to the terminal of the π-conjugated polymer in the present invention.

The preferred molecular weight of the π-conjugated polymer of the present invention is a polystyrene-equivalent number average molecular weight of 1000.
It is -1 million, More preferably, it is 5000-500000, Most preferably, it is 10000-100,000. When the molecular weight is too small (less than 1000), the film formability such as generation of cracks is deteriorated and the practicality becomes poor. On the other hand, when the molecular weight is large (more than 1000000), the solubility in a general organic solvent is deteriorated, the viscosity of the solution becomes high, and the coating becomes difficult, which is a practical problem.

  The π-conjugated polymer obtained as described above is used after removing impurities such as a catalyst, unreacted monomer, terminal terminator, and ammonium salt produced as a by-product during polymerization. These purification methods include conventional methods such as reprecipitation, column chromatography, adsorption, extraction (including Soxhlet extraction), ultrafiltration, dialysis, and the use of scavengers to remove the catalyst. Can be used.

  In order to make the π-conjugated polymer of the present invention obtained by the above-described production method into a thin film, a known film formation method such as a spin coating method, a casting method, a dipping method, an ink jet method, a doctor blade method, a screen printing method, or the like is used. be able to. Thereby, it is possible to produce a good thin film excellent in strength, toughness, durability, etc. without cracks, and suitably used as a material for various functional elements such as a photoelectric conversion element, a thin film transistor element, and a light emitting element. Can do.

Specific examples of the π-conjugated polymer represented by the general formula (I) thus obtained are shown below.
In the general formula (I), when Ar represents a substituted or unsubstituted arylene or heteroarylene, examples of Ar include the following.

Benzene, naphthalene, biphenyl, terphenyl, quarterphenyl, pyrene, fluorene, 9,9-dimethylfluorene, azulene, anthracene, triphenylene, chrysene, 9-benzylidenefluorene, 5H-dibenzo [a, d] cycloheptene, [2,2 ] -Divalent groups such as paracyclophane, triphenylamine, thiophene, bithiophene, terthiophene, quarterthiophene, thienothiophene, benzothiophene, dithienylbenzene, (furan, benzofuran, carbazole), benzodithiazole, etc. These may have a substituted or unsubstituted alkyl group, alkoxy group, thioalkoxy group, or halogen group as a substituent.
The substituted or unsubstituted alkyl group is a linear, branched or cyclic alkyl group having 1 to 25 carbon atoms, and these alkyl groups are further halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, iodine atom). ), A cyano group, a phenyl group, or a phenyl group substituted with a linear or branched alkyl group.

Specifically, methyl group, ethyl group, n-propyl group, i-propyl group, t-butyl group, s-butyl group, n-butyl group, i-butyl group, pentyl group, hexyl group, heptyl group, Octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecane group, hexadecyl group, heptadecyl group, octadecyl group, 3,7-dimethyloctyl group, 2-ethylhexyl group, trifluoromethyl group , Trifluorooctyl group, trifluorododecyl group, trifluorooctadecyl group, 2-cyanoethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, cyclopentyl group, cyclohexyl group and the like.
In the case of a substituted or unsubstituted alkoxy group or thioalkoxy group, specific examples include those in which an oxygen atom or a sulfur atom is inserted into the bonding position of the alkyl group to form an alkoxy group or a thioalkoxy group.

The π-conjugated polymer of the present invention is improved in solubility in a solvent due to the presence of an alkyl group, an alkoxy group, or an alkylthio group. In particular, the solubility can be improved, and the manufacturing tolerance of the wet film forming process is increased when manufacturing a photoelectric conversion element, a thin film transistor element, a light emitting element, and the like. For example, the choice of coating solvent is expanded, the temperature range during solution preparation is expanded, the temperature and pressure range during solvent drying is expanded, and high-quality thin films with high purity and high uniformity due to their high processability. Is obtained.
In addition, the π-conjugated polymer of the present invention includes a benzothieno [3,2-b] benzothiophene group having a condensed polycyclic structure, so that the ionization potential is relatively high and the stability against oxidation is relatively high. Therefore, stable device properties can be expected as electronic device and optical-electronic device characteristics.

  A more specific structural example of the general formula (I) of the π-conjugated polymer of the present invention is shown below.

(Here, I represents an integer of 1 to 4, and R represents hydrogen, aliphatic or alicyclic alkyl having 1 to 22 carbon atoms, halogen, or aliphatic or alicyclic carbon having 1 to 25 carbon atoms. A group selected from alkyl of 1 to 25, alkoxy having 1 to 25 carbons, thioalkoxy having 1 to 25 carbons, nitro, cyano, sulfone, and sulfoxide. May be different.)
Further detailed examples of the π-conjugated polymer of the present invention will be shown.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples unless it exceeds the gist.

Production Example 1:
[Monomer synthesis]
(Synthesis of dihalogen)
The dihalogen used for producing the conjugated polymer of the present invention is Zh. Org. Khim. 16, 2, 383 (1980) and J.A. Am. Chem. Soc. 128, 12604 (2006) with reference to Scheme 1 below to obtain monomer 7 dihalogen.

The analysis results of the monomer (dihalogen compound: iodide in this case) 7 in the above scheme 1 are shown below.
¹ H NMR (400 MHz, CDCl ₃ , TMS, δ): 7.62 (d, 2H, J = 8 Hz), 7.75 (dd, 2H, J1 = 8 Hz J2 = 4 Hz), 8.26 (d, 2H, J = (4 Hz)
Mass spectrometry: MS m / z = 492 (M +)
Elemental analysis: C, 34.40; H, 1.19 (actual value) C, 34.17; H, 1.23 (calculated value)
Melting point 300 ° C. or higher The structure inferred from the NMR, elemental analysis, mass spectrometry, and melting point values described above was the same as that of dihalogen 7 (Note that the NMR shift value is described in J. Am. Chem. Soc. , 128, 12604 (2006), there is a description about the same compound, which is different from what we synthesized.).

(Synthesis of diboron)
Diboron bodies (for example, shown in the following 11 and 15) used for the conjugated polymer were synthesized according to the following schemes 2 and 3.

The analysis results of the diboron body 11 obtained in the above scheme 2 are shown below.
¹ H NMR (400 MHz, CDCl ₃ , TMS, δ): 7.47 (s, 2H), 3.75 (s, 8H), 2.78 (t, 4H, J = 8 Hz), 1.23-1.30 (m, 36H), 1.56 (quint, 4H, J = 8 Hz), 1.03 (s, 12H), 0.88 (t, 6H, J = 8 Hz)
Melting point: 89.5-90.0 ℃

The analysis results of the diboron body 15 obtained in the above scheme 3 are shown below.
¹ H NMR (400 MHz, CDCl ₃ , TMS, δ): 7.08 (s, 2H), 3.93 (t, 4H, J = 8 Hz), 1.75 (quint, 4H, J = 8 Hz), 1.55-1.45 ( m, 4H), 1.36-1.26 (m, 56H), 0.88 (t, 6H, J = 8 Hz)
Melting point: 92.7-94.5 ℃

[Example 1]
The synthetic polymerization of the conjugated polymer was performed with reference to the description of Macromolecules (2000), 33, 5347-5352. Polymerization was performed using the following two types of monomer components.

350 mg (0.714 mmol) of 2,7-diiodobenzothieno [3,2-b] benzothiophene represented by the general formula (V) in a four-necked flask equipped with a water-cooled cooling pipe and a gas introduction pipe And 456 mg (0.714 mmol) of diboronic acid ester represented by the above general formula (VI) and (above monomer component), 114 mg (2.86 mmol) of sodium hydroxide, 20.4 mL of dimethylacetamide, 3 mL of toluene After taking 2.3 mL of water and replacing the inside of the container with argon gas, 24.8 mg (0.021 mmol) of tetrakistriphenylphosphine palladium was added, and the mixture was kept at 120 ° C. for 26 hours while stirring with a mechanical stirrer. Further, 32.9 mg (0.27 mmol) of phenylboronic acid was added and heated for 3 hours, and then 56.6 mg (0.36 mmol) of bromobenzene was added and heated to 120 ° C. for 3 hours, and then allowed to cool to room temperature. The resulting mixture was poured into 500 mL of MeOH / H ₂ O (4/1) and the precipitate was collected by filtration and washed with MeOH / H ₂ O, MeOH. Further, the precipitate is dissolved in a THF solution, recovered by reprecipitation from 900 mL of MeOH, and subsequently reprecipitated from 600 mL of acetone, and again dissolved in 50 mL of chloroform, so that the conductivity of the cleaning liquid becomes equivalent to that of ion-exchanged water. Repeated washing with water. Finally, 50 mL of a chloroform solution of the polymer was reprecipitated from 700 mL of MeOH, and the obtained polymer was collected by filtration, dried by heating under reduced pressure, and a pale yellow polymer represented by the following formula (VII) (yield: 240 mg, yield 50.0%).

The molecular weight in terms of polystyrene by gel permeation chromatography of the pale yellow polymer was as follows.
Number average molecular weight 8774, weight average molecular weight 19335
The obtained polymer showed good solubility in chloroform, chlorobenzene, toluene, xylene, THF (tetrahydrofuran) and the like, but was insoluble in methanol, acetone, DMF and the like.
The melting point was 228 ° C. (visual measurement using a melting point measuring machine equipped with a microscope and a hot stage and measurement by DSC).
FIG. 1 shows an infrared absorption spectrum of a polymer (casting) obtained by casting this polymer on a NaCl plate from a chloroform solution.
Further, FIG. 2 shows an SEM image of a polymer film formed by spin coating from a chloroform solution of this polymer and dried at 80 ° C. for 30 minutes in an Ar atmosphere (10,000 × magnification).

[Film formation of the polymer prepared in Example 1]
The polymer represented by the formula (VII) synthesized in Example 1 was dissolved in chloroform, toluene, xylene and THF at a concentration of 1 wt%, and passed through a filter to prepare a solution.
From each solution, a polymer film was formed on an ITO substrate and a silicon substrate by spin coating or casting. A smooth continuous film was obtained with either solution.
Moreover, the ionization potential calculated | required by cyclic voltammetry (made by Hokuto Denko) and AC-2 (made by Riken Keiki Co., Ltd.) using these membranes was 5.9 eV.

[Example 2]
Synthesis of conjugated polymers

  Polymerization was conducted in the same manner as in Example 1 except that the diboronic acid ester was changed from the formula (VI) to the above formula (VIII), and the brown polymer represented by the following formula (IX) (yield 364 mg, yield) 53.8%).

The molecular weight of the brown polymer in terms of polystyrene by gel permeation chromatography was as follows.
Number average molecular weight 5537, weight average molecular weight 7949
The obtained polymer showed good solubility in chloroform, chlorobenzene, toluene, xylene, THF (tetrahydrofuran) and the like, but was insoluble in methanol, acetone, DMF and the like.
The melting point was 309 ° C. (visual measurement using a melting point measuring machine equipped with a microscope and a hot stage and measurement by DSC).
FIG. 3 shows an infrared absorption spectrum of a polymer (casting) obtained by casting this polymer on a NaCl plate from a chlorobenzene solution.

[Film formation of the polymer prepared in Example 2]
The polymer represented by the formula (IX) synthesized in Example 2 was dissolved in chloroform, toluene, xylene, and THF at a concentration of 1 wt%, and passed through a filter to prepare a solution.
From each solution, a polymer film was formed on an ITO substrate and a silicon substrate by spin coating or casting. A smooth continuous film was obtained with either solution.
Moreover, the ionization potential calculated | required by cyclic voltammetry (made by Hokuto Denko) and AC-2 (made by Riken Keiki Co., Ltd.) using these membranes was 5.6 eV.

[Comparative Example 1]
As Comparative Example 1, a film was formed in the same manner as in Example 1 except that the polymer of Example 1 was changed to poly-3-hexylthiophene, and the ionization potential was measured.
Although it was dissolved in chloroform at a concentration of 1 wt%, the solubility of other solvents was at most about 0.5 wt%. Also, depending on the solution, there is a case where rapid crystallization occurs and a continuous film cannot be obtained.
The ionization potential of this polymer was 4.9 eV.

[Comparative Example 2]
Film formation and ionization potential were measured in the same manner except that the polymer of Example 1 was changed to 2,7-diphenylbenzothieno [3,2-b] benzothiophene.
Although it was slightly soluble in chloroform, it was not soluble at all in other solvents.
The ionization potential of this material was 5.4 eV.
The above results are shown in Table 1.

  From the above results, it was suggested that the polymer of the present invention has a high solubility in a general-purpose solvent, a film-forming property that is not influenced by the solvent, and a high oxidation stability.

  The π-conjugated polymer of the present invention is excellent in processability because it can be dissolved in various solvents, and can be applied to electronic devices such as semiconductors and optical-electronic devices such as EL light-emitting elements using such polymers. there is a possibility.

2 is an IR spectrum of the polymer of Example 1. The vertical axis represents the absorbance (% T:% -Transmittance), and the horizontal axis represents the wave number (cm ⁻¹ ). It is a SEM image (scanning electron microscopy) of the polymer film of Example 1 dried at 80 ° C. (magnification 10,000 times). 3 is an IR spectrum of the polymer of Example 2. The vertical axis represents the absorbance (% T:% -Transmittance), and the horizontal axis represents the wave number (cm ⁻¹ ).

Claims (2)

A polymer containing a benzothieno [3,2-b] benzothiophene structure having a repeating unit represented by the following general formula (I):
(In the formula, Ar is a divalent group which may have a substituent, and the divalent group is any one of thiophene, bithiophene, terthiophene, quarterthiophene, phenyl, biphenyl, terphenyl and quarterphenyl. A group selected from more.)   In the general formula (I), when Ar has a substituent, the substituent is an aliphatic or alicyclic carbon having an aliphatic or alicyclic alkyl group having 1 to 22 carbon atoms, halogen, or halogen. The number of substituents is a group selected from an alkyl group having 1 to 25 carbon atoms, an alkoxy group having 1 to 25 carbon atoms, a thioalkoxy group having 1 to 25 carbon atoms, a nitro group, a cyano group, a sulfone group, and a sulfoxide group. The polymer according to claim 1, wherein a plurality of substituents may be the same or different.