JPS5827601B2 - Semiconductive polymer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in semiconducting polymer compositions in which an organic semiconductor is dispersed in a matrix polymer.

Conventional organic semiconductors include those made of organic crystals and polymer organic semiconductors.

Various studies have been conducted on organic crystals, but they do not have the moldability of polymers, are not stable enough to rival inorganic semiconductors, and are difficult to obtain large single crystals, making it difficult to demonstrate the characteristics of organic materials. .

On the other hand, polymeric organic semiconductors have charge transfer bonds and conjugated π-electron bonds in the polymer chains themselves, so they have a rigid structure, and they do not have good moldability like general-purpose polymers, and are brittle and have no film-forming properties. There are many things.

It is well known that semiconducting polymer compositions can be obtained by dispersing carbon, metals, or organic semiconductors in insulating polymers, but when an organic semiconductor is dispersed in a matrix polymer, Its characteristic feature is that it is easily molecularly dispersed.

When an organic semiconductor is molecularly dispersed in a matrix polymer, the electrical properties of the polymer composition are close to those of an intrinsic semiconductor, a model diagram of which is shown in FIG.

On the other hand, in the case of an intrinsic polymeric organic semiconductor, as shown in Figure 2, the movement and gaps of the polymeric main chain 1 affect the stacking of π-electron-based conductive sites 2, but most of the π-electron-based conductive sites 2 are Rather than contributing to stacking of the system's conductive sites, the torsion and rigidity of the polymer backbone impede stacking.

In terms of mechanical properties, there is a very large difference between Fig. 1 and Fig. 2. The one in Fig. 1 has moldability similar to that of a general-purpose polymer, while the one in Fig. 2 has a (bul
ky ) π-electron-based conductive sites have strong chemical bonds with the main chain of the polymer, resulting in a brittle polymer with poor moldability.

However, although compositions in which an organic semiconductor is molecularly dispersed in a polymer matrix have excellent processability, the organic semiconductor becomes dissolved in the polymer and causes electrophoresis due to an electric field, which causes charge transfer. When it is a complex, it has the disadvantage that it becomes a cation and an anion and causes ionic conduction at the same time.

In these cases, the application of an electric field causes mass transfer between the electrodes, causing changes in the material composition and structure, resulting in the inability to obtain a stable electron conduction current.

Conventionally, a charge transfer complex consisting of an electron donor and an electron acceptor has often been used as an organic semiconductor for forming this type of semiconducting polymer composition.

These charge transfer complexes include ionic or nonionic charge transfer molecular compounds as well as ionic radical salts.

In these organic semiconductors, carriers for electron conduction are classified into n-type and p-type depending on whether they are electrons or holes, but electrons in a stable radical state contribute to conduction, and these radicals form molecules that serve as carrier sites. Existing.

Therefore, in the above complex, a molecule having an ionic radical state becomes a carrier site, and in the case of an anion radical, it becomes an n-type, and in the case of a cation radical, it becomes a p-type.

In addition, charge transfer type molecular compounds exhibit NTP amphoteric conduction, and ionic molecular compounds exhibit complex crystalline state, where holes and electrons flow through independent columns of cation radicals and anion radicals, respectively. There are many.

Various compounds that create stable cation radicals and anion radicals are known, but all of them are low molecules with a developed π-electron system, and generally use onium cations or metal ions as electron donors to create anion radicals. Many anion radical salts have been synthesized that use .

These conventional complexes having ion radicals have the disadvantage that they are difficult to disperse in molecules in a polymer matrix, and when they are well dispersed, they move in the matrix due to an electric field and undergo structural changes.

On the other hand, in the case of polymer semiconductors, conventional polymer semiconductors have a structure as shown in Figure 2 and have poor machinability. The majority of them were anion radical salts with -tetracyanoquinodimethane (hereinafter referred to as TCNQ).

In these studies, the polycation is a polymer, but the TCNQ ion radical serving as a carrier site is a low molecule, and TCNQ is arranged under the influence of the ionic site of the polycation.

There have also been attempts to disperse this polymer complex of polycation and TCNQ in another polymer matrix;
In this case, the polycation is polymerized and fixed, but TCNQ, which is a carrier site, is a low molecule and is important for electron conduction, but there is a problem in that it is not fixed.

The present invention aims to improve these drawbacks and provide a polymer composition that has excellent moldability and exhibits stable electron conduction properties.

That is, it is characterized in that a compound consisting of a low polymer of ion radical molecules serving as carrier sites is used as an organic semiconductor that is molecularly dispersed in a polymer matrix.

According to the present invention, as a result of polymerization of molecules that form stable radical states that serve as carrier sites, mass transfer in the polymer matrix is greatly hindered, giving priority to electron conduction, resulting in stable electron conduction. A polymer composition can be obtained.

Here, as the ion radical molecules to be polymerized, those already known can be used.

Examples of compounds that create stable cation radicals include N, N, N', N'-tetramethylarphenylenediamine, tetrathiofulvalene, tetraselenofulvalene, tetrathiotetracene, dibenzophenothiazine, and many other nitrogen-containing compounds. There are compounds and sulfur-containing compounds.

On the other hand, compounds that create stable anion radicals include haloquinone, cyanoquinone, tetracyanoethylene, and TCN.
In addition to Q, tetracyatunafuchinodimethane, there are many cyanides and halides, and among them, TCNQ is one of the most excellent anion radicals.

A good way to polymerize ion radical molecules is to attach a functional group as a side chain at a position that does not impair the stability of the ion radical, and then polymerize it. In addition to bonds, ether bonds, and vinyl bonds, many bonds such as methylene bonds and imide bonds formed by condensation of formaldehyde can be used.

Among these, bonds that can impart flexibility with a high degree of rotational freedom to the material, such as urethane bonds, ester bonds, and ether bonds, and that also improve compatibility with the polymer matrix (IJ) are desirable.

As a representative of ion radical molecules, TCNQ * books are explained, for example, J, Org, Chem.

1(8), 1412 (1978), using urethane linkages.

That is, a polymer can be obtained by reacting a TCNQCN-l molecule produced by introducing a diol-type alkoxy group as a side chain into TCNQ with a diisocyanate.

Its structure is expressed as follows: The alkoxy groups are introduced into TCNQ at positions 2.3 and 5.6, which do not destroy the stability of the ionic radicals of TCNQ.

In the present invention, a low polymer of the polymer thus obtained, that is, an oligomer is used, and a charge transfer complex of this low polymer is molecularly dispersed in a polymer matrix I-IJ.

The reason for using a low polymer is to avoid deteriorating the compatibility with the polymeric matrix, and also to prevent the charge transfer image polymer from interfering with the processability during molding of the composition, and vice versa. This is because the immobilization of carrier sites (ion radical molecules), which is the object of the present invention, can be sufficiently achieved by such oligomer-level polymerization.

It is sufficient for the degree of polymerization P of this low polymer to be P=2 to 20.

If it exceeds this range, the processability of a composition in which it is molecularly dispersed tends to deteriorate significantly.

In the present invention, these low polymers of ion radical molecules are dispersed in a polymer matrix in the form of ion radical salts or charge transfer type molecular compounds.

Therefore, in the case of charge-transfer molecular compounds, both the cationic and anionic radical molecules are polymerized separately or together, and in the case of ionic radical salts, one ionic radical molecule is polymerized while the other The ion may be a low molecular weight ion or a polymer.

However, in order to prevent ion conduction, it is better to polymerize these ions as well.

Examples of this type of polymerized ion include polycations and polyanions such as polyvinylpyridine, polyaminostyrene, and i-ion used in polymer electrolytes.

Also, metal beam bonding can be used.

These low polymer ion radical salts and molecular compounds of ion radical molecules used in the present invention are polymerized with bonds that do not impair the stability of ion radicals.
Ion radicals are stable and conductivity is not severely impaired.

In the present invention, by molecularly dispersing this low degree of polymerization complex in the polymer matrix I-IJ, a carrier site that is strongly fixed and difficult to move in the polymer matrix I-IJ is formed, and mass transfer is prevented. , provides a composition in which structural changes do not occur much and stable electronic conduction is prioritized.

As the polymer matrix used in the present invention, one having a structure in which the above-mentioned organic semiconductors are molecularly dispersed may be selected and used.The larger the Coulomb potential is, the easier electron conduction is. It goes without saying that it may be used in combination with

Next, examples of the present invention will be shown.

A low polymer polyurethane was obtained by reacting with 0.08 mol of Na salt of TCNQ alkoxylated with ethylene glycol.

30 parts by weight of this was added to 100 parts by weight of thermoplastic polyurethane, and the mixture was kneaded with heated rolls to form a sheet.

When this resistance was measured, the specific resistance was 5.
9X109. It is O-snoring, and direct current is applied at 60℃ (
Resistance change R after 100 hours due to 500V/cIrL)
/Ro was extremely small and was 1.8 times.

On the other hand, in a composition in which 5% by weight of NaTCNQ is molecularly dispersed in the same thermoplastic polyurethane, the specific resistance at 35°C is 3.6° x 109. ! 12-α, and the resistance change R/Ro due to the same direct current application at 60° C. was as large as 24 times.

The present invention provides a semiconductive polymer composition having such excellent processability, and can be used for various purposes as an organic electronic material.

For example, it can be used as a material for plastic thermistors or as a material for many functional composite materials in combination with inorganic semiconductor particles.

[Brief explanation of drawings]

The drawing shows a model of electrical conduction in a semiconductive polymer material, and Figure 1 shows a semiconductive polymer composition in which π-electron conductive sites are molecularly dispersed in a Marx polymer. FIG. 2 shows an intrinsic polymeric organic semiconductor in which a matrix polymer and a π-electron conductive site are chemically bonded.

Claims (1)

[Scope of Claims] 1. A semiconducting polymer composition comprising an organic semiconductor molecularly dispersed in a polymer matrix, wherein the organic semiconductor is composed of a low polymer of ion radical molecules serving as a carrier site. A semiconductive polymer composition characterized by being a compound. 2 The ion radical molecule serving as the carrier site is
The semiconductive polymer composition according to claim 1, which is a sulfur-containing compound or a nitrogen-containing compound that forms cation radicals. 3 The ion radical molecule serving as the carrier site is
The semiconductive polymer composition according to claim 1, which is a cyanide compound or halide that forms anion radicals. 4 The cyano compound is 7,7,8.8-tetracyanoquinodimethane, and its polymerization position is 2°3.5,6
The semiconductive polymer composition according to claim 3, which is at least one of: 5. The low polymer is polymerized by at least one selected from the group consisting of urethane bonds, amide bonds, ester bonds, ether bonds, and vinyl bonds. semiconducting polymer composition. 6. The semiconductive polymer composition according to any one of claims 1 to 4, wherein the low polymer has an average degree of polymerization of 2 to 20.