JPH08134189A - Pi-conjugated polymer - Google Patents

Abstract

PURPOSE: To obtain the subject polymer containing specific phenylenevinylene units and specific naphthalenevinylene units as main repeating units, excellent in processing properties such as solubility and meltability, showing a thermal transition type liquid crystal phase, and useful as an organic electronic material, etc. CONSTITUTION: This polymer comprises (A) 1,4-phenylenevinylene units of formula I and (B) 2,6-naphthalenevinylene units of formula II as main repeating units in a ratio of 0.1:0.9 to 0.9:0.1, preferably 0.2:0.8 to 0.8:0.2. The polymer is obtained e.g. by subjecting p-xylylene dihalide and 2,6-bishalomethylnaphthalene to a hydrogen halide-removing reaction using a base such as potassium tert- butoxide or sodium hydride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a π-conjugated polymer, and more particularly to a π-conjugated polymer used as an organic electronic material and the like.
It has excellent processability such as solubility and meltability, and exhibits a heat-transition type liquid crystal phase (thus, the molecular orientation can be easily controlled).
It relates to a π-conjugated high molecular polymer.

[0002]

2. Description of the Related Art Polyarylene vinylene (hereinafter referred to as PAV), which is a chain polymer in which aromatic rings and vinylene groups are alternately connected
Is known as one of π-conjugated conductive polymers.

As such PAVs, polyparaphenylene vinylene containing benzene as a repeating unit [hereinafter referred to as PPV], poly (1,4-naphthalene vinylene) containing naphthalene as a repeating unit and poly (2,6- Naphthalenevinylene) [hereinafter referred to as 2,6-PNV], poly (2,5-thienylenevinylene) containing thiophene as a repeating unit, and the like have been synthesized. Since each of these has high conductivity in the state of being doped with an electron acceptor or an electron donor, and has the characteristic of being relatively stable in the atmosphere,
Active research and development is underway. Furthermore, recently, Bu
Inventions by rroughes, etc. [JH Burrough-es, DDC Bra
dly, AR Brown, RN Marks, K. Mackay, RH Frin
d, PLBurns, and AB Holms, Nature, vol. 347,
p.539 (1990)] since then, attention has been focused on its application as a display device or a light emitting device utilizing high luminous efficiency.

[0004]

One of the problems with the conventional PAV is that it is generally insoluble and infusible and poor in processability when its polymerization degree is sufficiently high. In this regard, introduction of a methoxy group or an alkoxy group having a longer chain length into the aromatic ring has been proposed as an improvement measure. According to this, the solubility in an organic solvent is improved to some extent, and a thin film can be formed by spin coating or the like. More recently, an alkoxy-substituted PAV [poly (2,5-dinonyloxy-p-] which exhibits a liquid crystal phase of thermal transition, that is, meltable and capable of forming a self-alignment
Phenylene vinylene)] has been reported [M.Hamaguch
i and K. Yoshino: Jpn.J.Appl.Phys., vol.33, p.L1478 (1
994)]. However, in general, an alkyl group or an alkoxy group is a component that does not itself contribute to conductivity (electrical conductivity occurs along the π-conjugated PAV main chain), so a bulky substituent is introduced to improve processability. If you do
It is unavoidable that the conductivity (conductivity) is slightly lowered.

On the other hand, since PAV is a rigid linear polymer, the physical properties of the material are naturally strongly influenced by the orientation of the molecules in it. For example, electrical conduction occurs more easily along a molecular chain than in a direction perpendicular to the molecular chain. Moreover, the mechanical strength is also better in the direction of the molecular chain. Therefore, in order to optimize the physical properties of the material, it is necessary to control the orientation of molecular chains.

From the above, various methods have been devised for producing PAVs having high crystallinity or orientation and excellent workability (solubility, meltability, etc.). A typical example thereof is a method utilizing a soluble precursor polymer of PAV. That is, a soluble precursor polymer of PAV is first synthesized, dissolved in a suitable solvent such as water, molded by a method such as spin coating, and stretched at this stage to orient the molecular chains and then heat treated. By doing so, it is converted into PAV. However,
This method leaves many problems to be solved, such as complicated operation, difficulty in molding to a predetermined shape and size, and inability to mold a thin film on a substrate.

The present invention has been made by paying attention to such a situation, and its object is a π-conjugated high-performance material having excellent workability such as solubility and meltability as compared with the conventional PAV. It is an object of the present invention to provide a molecular polymer, and further to provide a π-conjugated high molecular polymer capable of exhibiting a heat transition type liquid crystal phase and easily controlling the molecular orientation.

[0008]

In order to achieve the above object, the π-conjugated high molecular polymer according to the present invention has the following constitution. That is, the π-conjugated high molecular polymer according to claim 1 is a 1,4-phenylene vinylene unit represented by the following chemical formula (1) and a 2,6-phenylene vinylene unit represented by the following chemical formula (2).
-A naphthalene vinylene unit as a main repeating unit, and the content ratio of each is 0.1: 0.
It is a π-conjugated high molecular polymer characterized by being 9 to 0.9: 0.1.

Embedded image

[Chemical 4]

In the π-conjugated high molecular polymer according to claim 2, the content ratio of the 1,4-phenylene vinylene unit and the 2,6-naphthalene vinylene unit is 0.2: 0.
The π-conjugated high molecular polymer according to claim 1, which has a ratio of 8 to 0.8: 0.2.

[0010]

The function of the π-conjugated high molecular polymer according to the present invention is as described above. In other words, this high-molecular polymer is a copolymer type PAV in which naphthalene and benzene are bonded at the 2,6-position and the 1,4-position, respectively, and the content ratio of each is expressed by molar ratio. 0.1: 0.9 to 0.9: 0.1
It is what With such a molecular structure, processability such as solubility and meltability can be imparted without impairing properties such as conductivity. Furthermore, when the above content ratio is set to a molar ratio of 0.2: 0.8 to 0.8: 0.2, this high molecular polymer exhibits a heat transition type liquid crystal phase. Therefore, if the formation of orientational order in the liquid crystal phase is used, the material The orientation of the molecular chains in can be easily controlled.
That is, it is possible to control the orientation by a magnetic field or an electric field, or to form the orientation by shear stress. Further, a highly oriented fibrous polymer can be obtained by spinning in a molten state.

The details will be described below. As mentioned above, PAVs without substituents such as alkoxy groups
Are generally insoluble and infusible powders. It is understood that this is because the PAV molecule is linear and has relatively high symmetry, and therefore forms a highly crystalline molecular texture strongly bound by Van der Waals forces. And the effect of the substituent such as an alkoxy group weakens the intermolecular interaction,
It is thought to be to increase the affinity with the solvent.

Therefore, the present inventors examined the relationship between the skeletal structure of PAV and the physical properties, and as a result, made a copolymerized PAV containing both benzene and naphthalene as repeating units, Molar ratio
It was found that if the ratio is 0.1: 0.9 to 0.9: 0.1, processability can be imparted without impairing the characteristics of PAV as a π-conjugated polymer, and the present invention has been completed.

That is, both pure PPV and 2,6-PNV have too strong an intermolecular interaction to be dissolved or melted in an organic solvent, but when they are copolymerized with each other, the symmetry of the molecule is lowered. Therefore, it becomes soluble and fusible. That is, processability can be imparted without impairing the characteristics of PAV as a π-conjugated polymer such as conductivity.

Based on this finding, the π-conjugated high molecular polymer according to the present invention is a copolymerized PAV containing both benzene and naphthalene as repeating units, that is, 1,4-
A π-conjugated polymer having a phenylene vinylene unit and a 2,6-naphthalene vinylene unit as a main repeating unit, and containing the 1,4-phenylene vinylene unit and the 2,6-naphthalene vinylene unit. The molar ratio is 0.1: 0.9 to 0.9: 0.1 (the π-conjugated high molecular weight polymer according to claim 1).

Therefore, the π-conjugated high molecular polymer according to the present invention is excellent in processability such as solubility and meltability as compared with the conventional PAV. That is, compared with the conventional PAV, the workability such as solubility and meltability is excellent, and other properties such as conductivity are excellent as in the conventional PAV. Also, a PAV of a type in which a substituent such as the above-mentioned alkoxy group is introduced into an aromatic ring
Compared with, the solubility and the meltability are extremely excellent, and the conductivity is slightly excellent. Compared with the method using the soluble precursor polymer of PAV, the PAV can be synthesized in one step, so that the operation in the production is extremely simple and the moldability into a predetermined shape and size is remarkably excellent. It is excellent in that it can be formed into a thin film.

Here, the content ratio (molar ratio) of the 1,4-phenylenevinylene unit and the 2,6-naphthalenevinylene unit of 0.1: 0.9 to 0.9: 0.1 is based on the experimental result. When the molar ratio is less than 0.1: 0.9, the number of 2,6-naphthalenevinylene units is too large and the intermolecular interaction is strong, so that the solubility and meltability are deteriorated and insufficient. This is because there are too many 4,4-phenylenevinylene units and the intermolecular interaction is strong, so that the solubility and the meltability are lowered and become insufficient.

When the content ratio of the 1,4-phenylene vinylene unit and the 2,6-naphthalene vinylene unit is 0.2: 0.8 to 0.8: 0.2 in terms of molar ratio, the molecule is rod-shaped,
Moreover, since it is moderately rigid, it exhibits a heat transition type liquid crystal phase,
By utilizing the formation of the orientational order in the liquid crystal phase, the orientation of the molecular chains can be easily controlled, and thus the orientation can be enhanced (the π-conjugated polymer polymer according to claim 2). . In this case, it is considered that the 2,6-naphthalenevinylene unit plays a role of a crankshaft in the field of liquid crystal engineering for the PPV molecule. That is, the liquid crystal temperature of PPV, which would otherwise exceed the thermal decomposition temperature due to strong intermolecular interaction without it, is lowered by the introduction of rotational motion about the axis connecting the 2 and 6 positions of the naphthalene unit. It is presumed to be a thing.

The π-conjugated high molecular polymer according to the present invention is
It can be synthesized using a known method. For example, p
-Xylylenedihalide and 2,6-bishalomethylnaphthalene can be synthesized by dehydrohalogenating with a base such as potassium tert-butoxide or sodium hydride. At this time, chlorine, bromine or iodine is suitable as the halogen element in the raw material. Alternatively, it can also be obtained by the Wittig reaction using a diphosphonium salt and a dialdehyde.

In the π-conjugated polymer according to the present invention, it is possible to introduce various substituents, if necessary, to change the physical properties, as in the case of the known PAV. For example, in general, by introducing an alkyl group into a benzene ring or a naphthalene ring, the softening and melting temperature of the polymer can be further lowered or the solubility can be increased. The optical band gap can be changed by introducing a methoxy group or an alkoxy group having a larger chain length. Also, a report by Greenham et al. [NC Greenham, SC Mora
tti, DDC Bradly, RH Friend, and AB Holms,
Nature, vol.365, p.628 (1993)], one hydrogen of the vinylene group is replaced with a cyano group, or a non-conjugated structure such as a methylene group in the PAV polymer main chain. It is also possible to fabricate an EL element that emits blue light, which is generally difficult with a light emitting diode based on an inorganic material, by partially introducing the compound to reduce the π conjugation length.

The π-conjugated high molecular polymer according to the present invention is
Since it is soluble and fusible, it can be processed into a desired shape by using a known method just like ordinary plastics. For example, the above polymer can be dissolved in a suitable solvent such as chloroform, toluene or tetrahydrofuran to prepare a solution, which can be spin-coated or cast to form a thin film. Alternatively, it is possible to perform hot pressing, injection molding or melt spinning by utilizing its meltability. It is also possible to form a thin film by vacuum vapor deposition as described in JP-A-62-250166.

[0021]

[Examples] p-xylylene dichloride and 2,6-bischloromethylnaphthalene were dissolved in tetrahydrofuran at a predetermined ratio (molar ratio shown in the column of monomer charging ratio in Table 1), and then, in an inert atmosphere, Polymerization was carried out by dehydrohalogenation reaction with potassium tert-butoxide at −10 ° C.
Then, the reaction mixture was poured into excess methanol,
The reaction was stopped and the produced polymer was precipitated. Next, this precipitate was collected by filtration and then dried to obtain a powdery polymer.

The polymer thus obtained, that is, π-
The softening point of the conjugated high molecular polymer was measured, and the liquid crystal forming property and the solubility in chloroform were examined. At this time, the softening point was measured by a microscope with a hot stage. The liquid crystal forming properties were examined by observing with a polarizing microscope equipped with a hot stage. Table 1 shows the liquid crystal transitions with ◯, and those without liquid crystal transitions with x. Regarding the solubility, Table 1 shows the solubility in chloroform of more than 30 wt% by ◯, that of 30 to 10 wt% by Δ, and less than 10 wt% by x.

[0023]

[Table 1]

As is clear from Table 1, when the charged amount of p-xylylenedichloride is 0% (the charged amount of 2,6-bischloromethylnaphthalene: 100%), that is, the obtained polymer is
Π- containing 2,6-naphthalene vinylene as a repeating unit
When it is a conjugated polymer (Comparative Example 1), and when the amount of 2,6-bischloromethylnaphthalene charged is 0% (the amount of p-xylylenedichloride charged: 100%), that is, 1,4-phenylenevinylene In the case of a π-conjugated polymer containing as a repeating unit (Comparative Example 2), the solubility is x (less than 10 wt%), the solubility is poor, and the decomposition temperature In the following, neither softening nor exhibiting a liquid crystal phase will occur.

On the other hand, the charged molar ratio of p-xylylene dichloride to 2,6-bischloromethylnaphthalene was
When 0.1: 0.9 to 0.9: 0.1, the obtained polymer is 1,4
-A phenylene vinylene unit and a 2,6-naphthalene vinylene unit as main repeating units, and their content ratio is 0.1: 0.9 to 0.9: 0.1 in molar ratio π-conjugated high molecular polymer (Example 1 to 7), the solubility is Δ (30 to 10 wt%) or ◯ (more than 30 wt%), the solubility is excellent, and they soften below the decomposition temperature.

In particular, the above-mentioned charging molar ratio is 0.2: 0.8 to
In the case of 0.8: 0.2, that is, the above content ratio is a molar ratio of 0.
In the case of the π-conjugated high molecular weight polymer having a ratio of 2: 0.8 to 0.8: 0.2 (Examples 2 to 6), the solubilities are all ○ (more than 30 wt%)
Therefore, the solubility is extremely excellent, the softening point is further lowered, and further, liquid crystal transition occurs, and a heat transition type liquid crystal phase is exhibited. Among them, the above content ratio (molar ratio) is 0.
In the case of 3: 0.7 to 0.7: 0.3 (Examples 3 to 5), and in the case of 0.5: 0.5 (Example 4), the softening point was lower, and although not shown in Table 1, the solubility was not shown. It was confirmed that the higher the temperature, the higher the meltability, the more easily the liquid crystal phase exhibits a heat transition type liquid crystal, and the more easily the orientation of the molecular chain can be controlled.

From the above, a liquid crystal phase of thermal transition type is exhibited,
In order to easily control the molecular orientation,
The content ratio (molar ratio) of 1,4-phenylene vinylene unit and 2,6-naphthalene vinylene unit is 0.2: 0.8 to 0.8: 0.
It turns out that 2 is better. Furthermore, as the content ratio (molar ratio) approaches 0.5: 0.5, the softening point becomes lower, and the properties such as solubility, liquid crystal forming property, and meltability are improved. The ratio (molar ratio) is 0.2:
From 0.8 to 0.8: 0.2 0.3: 0.7 to 0.7: 0.3,
Further, it is understood that it is better to set 0.4: 0.6 to 0.6: 0.4.

[0028]

As described above, the π-conjugated high molecular polymer according to the present invention has 1,4-phenylene vinylene units and
2,6-naphthalylenevinylene unit as a main repeating unit, and their content ratio (molar ratio) is 0.1:
It is a π-conjugated high-molecular polymer with 0.9 to 0.9: 0.1, and is superior in processability such as solubility and meltability as compared with the conventional PAV (polyarylene vinylene, which is a π-conjugated polymer). , Other properties such as conductivity are
It is as excellent as V, and therefore, can be processed into a desired shape or size relatively easily, and can exhibit high conductivity in a doped state, and thus is suitably used as an organic electronic material or the like. There is an effect that can be.

The above content ratio (molar ratio) is 0.2: 0.8.
To 0.8: 0.2, a thermal transition type liquid crystal phase is exhibited, and by utilizing the formation of orientational order in this liquid crystal phase, the orientation of molecular chains can be easily controlled, and therefore, The material properties such as electrical conductivity and mechanical strength can be easily changed, and the material properties can be easily optimized.

Claims (2)

[Claims] 1. A 1,4-phenylene vinylene unit represented by the following chemical formula (1) and 2,6 represented by the following chemical formula (2):
-A naphthalene vinylene unit as a main repeating unit, and the content ratio of each is 0.1: 0.
9 to 0.9: 0.1 π-conjugated polymer. Embedded image Embedded image 2. The π- according to claim 1, wherein the content ratio of the 1,4-phenylene vinylene unit and the 2,6-naphthalene vinylene unit is 0.2: 0.8 to 0.8: 0.2 in terms of molar ratio.
Conjugated polymer.