JPH08283415A - Production of polysilane - Google Patents

Abstract

PURPOSE: To obtain a polysilane having high molecular weight and narrow molecular weight distribution and useful as a photoconductive material, etc., in high yield by carrying out the polycondensation of a specific dihalosilane in a solvent in the presence of an alkali metal. CONSTITUTION: This polysilane is produced by the polycondensation reaction of (A) a dihalosilane of formula I or formula II [R1 and R2 are each a 1-22C (substituted)alkyl, a (substituted)alkoxy, a 6-22C (substituted)aryl or a (substituted)aryloxy; R3 is a 1-22C bifunctional organic group; X is Cl, Br or I; a, b and m are each 1-50] in (B) a solvent (e.g. toluene) containing a quaternary ammonium salt of formula III [R. to R7 are each a 1-20C (substituted)alkyl; at least one of R4 to R7 is a 6-20C (substituted)alkyl] using (C) an alkali metal (preferably dispersed in the form of fine particles of e.g. <=0.1mm diameter).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductive material, a non-linear optical material, and a method for producing polysilane useful as a precursor substance of a non-oxide ceramic having excellent heat resistance.

[0002]

2. Description of the Related Art Polysilane having a skeleton made of silicon-silicon bond and having various organic groups in side chains is a precursor material of silicon carbide ceramics (Yajima, Am.
Ceram.Soc.Bull., 62., 893 (1983)) and resist materials (Mi
ller, Materials for Microlithography, ACS Symposium
Ser.266, Cap.14, p293 (1984)).

Further, the polysilane has been noted for its high hole mobility, and its application to electrophotographic technology (US Pat.
4,618,551 (1986) / JP-A-61-170747),
Applications as conductive polymers, nonlinear optical materials and light emitting materials are expected (Miller, Chem. Review, 89, p1350 (198
9)).

Conventionally, the following methods have been known as a method for producing polysilane. (1) Dehalogenative condensation reaction of dihalosilane with alkali metal (Kipping method) (2) Dehydrogenative condensation of hydrosilane (Harrod, J. Organome
t. Chem., 279, C11 (1985)) (3) Ring-opening polymerization of cyclic compounds (Sakurai, J. Am. Chem. So
c., 111, p7641 (1989) / Matyjaszewski, ACS Symp.Ser.360,
p78 (1988)) (4) Condensation of lithiosilane and halosilane (Wesson, J. Pol)
ym.Sci., 19, p65 (1981)) desalination condensation (5) Electrochemical polymerization (Dunogues, J. Organomet. Chem.,
382, C17 (1990) / Ishikawa et al., JP 3-104893)

However, there are problems such that it is difficult to obtain a high molecular weight polymer by the methods (2) and (5), and monomer synthesis is difficult by the methods (3) and (4). For this reason, as the method for synthesizing polysilane, the Kipping method (1) is currently the only practical method.

According to the Kipping method, a polymer having a relatively high molecular weight can be obtained, but a polymer having a molecular weight of a level capable of exhibiting sufficient characteristics as a polysilane (specifically, a weight average molecular weight (Mw) of about 5,000 or more (polystyrene) Yield of (converted) is usually only about 5 to 25%, and a large amount of low molecular weight components mainly composed of cyclics is produced.
In addition, the obtained polysilane has a problem that it exhibits a wide molecular weight distribution (polymodal) ranging from several thousand to several million.
There has been a demand for a method for synthesizing polysilane having a narrower molecular weight distribution as the yield is improved.

Various attempts have been made to solve such problems, increase the polymer yield by the Kipping method, and narrow the molecular weight distribution. Miller et al. Reported that the yield of polydihexylsilane was 2% with a reactive additive such as ethyl acetate.
% To 6%, the yield of polymethylphenylsilane was 10
% To 15%. In addition, the amount of crown ether and naphthalene is 1 for each monomer.
It has also been reported that by adding ~ 2 mol%, 6% of a polymer can be obtained from a hardly polymerizable monomer such as bis (3,5-dimethoxyphenyl) dichlorosilane (Polymer Preprint, 35 (1), p500 (1994)).

Attempts have also been made to optimize the solvent to obtain high molecular weight polysilane in high yield.
Miller et al. Used a polymerization solvent such as diethylene glycol dimethyl ether (Diglyme) in combination with toluene to increase the yield of polydihexylsilane from 6% to 37%.
%, The yield of polyanisylmethylsilane from 12% to 2
It has been reported that the molecular weight distribution can be narrowed at the same time by increasing it to 5% (Materials for Microlithography, ACS Sympos
ium Ser.266, Cap.14, p293 (1984)).

[0009] Jones et al. Examined the effect of solvents and additives on the polymerization, taking methylphenyldichlorosilane as an example, and reported that a polymer was obtained in a yield of 58% when tetrahydrofuran was used as the solvent. Proceedings of the 2nd Symposium on Silicon Polymer Materials, Dec. 5-6 (1994), p121
). However, the molecular weight of the polysilane obtained is only a few thousand.

[0010] Matyjaszewski reported that in the Kipping method, by irradiating the reaction system with ultrasonic waves, polymerization can be carried out at room temperature, and a polymer having a narrow molecular weight distribution can be obtained in high yield (J. Am. .Chem.Soc., 110 (10), p3321 (1
988)).

At this time, it has been reported that the use of tetrahydrofuran or a mixed solvent of diglyme and toluene as the solvent lowers the molecular weight, but can improve the yield of the polymer (Polymer Preprint, 31, p278 (1990)). However, since the irradiation of ultrasonic waves breaks the Si-Si bond of polysilane,
There is a problem that the polysilane generated with long-time reaction is decomposed.

[0012]

The object of the present invention is to improve the problems of low yield and wide molecular weight distribution of the Kipping method, which is the only practical production method of polysilane, and to improve the It is an object of the present invention to provide a method for producing a polysilane having a high molecular weight and a narrow molecular weight distribution in a high yield.

[0013]

Means for Solving the Problems The present inventors have completed the present invention as a result of intensive studies on a synthesis method in order to solve the above problems in the Kipping method which is a synthesis method of polysilane.

The present invention comprises the following inventions. [1] General formula (1) or (2)

[Chemical 4]

[0015]

Embedded image (In these formulas, R ₁ and R ₂ are an alkyl group having 1 to 22 carbon atoms, a substituted alkyl group, an alkoxy group or a substituted alkoxy group, an aryl group having 6 to 22 carbon atoms, a substituted aryl group, an aryloxy group or a substituted aryloxy group. Shows the group
R ₁ and R ₂ may be the same or different from each other,
The arrangement of R ₁ and R ₂ may have a specific regularity. R ₃ represents a bifunctional organic group having 1 to 22 carbon atoms,
Each X independently represents chlorine, bromine or iodine atom.
a, b, and m show the integer of 1-50. ) Is represented by the general formula (3)

[0016]

[Chemical 6] (In the formula, R ₄ , R ₅ , R ₆ , and R ₇ are an alkyl group having 1 to 20 carbon atoms or a substituted alkyl group, and at least one of them is an alkyl group having 6 to 20 carbon atoms or a substituted alkyl group. , X represents chlorine, bromine or iodine atom), and polycondensation with an alkali metal is carried out in a solvent containing a quaternary ammonium salt represented by the formula (4).

[2] The method for producing a polysilane according to the above item (1), wherein the alkali metal is used in a state of being dispersed in fine particles.

The dihalosilane used in the synthesis of the polysilane of the present invention is represented by the general formula (1) or (2). As the raw material dihalosilane, these compounds may be used alone or as a mixture of both. In these formulas, R ₁ and R ₂ are preferably an alkyl group having 1 to 12 carbon atoms, a substituted alkyl group, an alkoxy group or a substituted alkoxy group, an aryl group having 6 to 20 carbon atoms, a substituted aryl group, an aryloxy group. Alternatively, it represents a substituted aryloxy group, R ₁ and R ₂ may be the same or different from each other, and the arrangement of R ₁ and R ₂ may have a specific regularity. R ₃ preferably has 1 to 2 carbon atoms
0 represents a bifunctional organic group, and a, b and m preferably represent an integer of 1 to 10.

Here, R ₁ and R ₂ are more preferably alkyl groups such as methyl, ethyl, isopropyl, t-butyl, methoxy and ethoxy groups, or aryl groups such as phenyl and naphthyl groups, and silicon The number of bonds a, b and m of is preferably 1 to 8. Also,
In the compound represented by the general formula (2), R ₃ is more preferably an alkylene group having 1 to 14 carbon atoms represented by methylene, ethylene, phenylene group and the like, an arylene group or an alkynylene group.

As the halogen of the dihalosilane represented by the general formula (1) or (2), bromine or iodine atom can be used in addition to the most general chlorine.

Examples of the alkali metal used in the present invention include lithium, sodium, potassium and alloys thereof. In particular, when the reaction is carried out below the melting point of these alkali metals, the alkali metals are dispersed in fine particles, preferably a particle diameter of 0.1 mm or less, and used. By using an alkali metal dispersed in fine particles, preferably with a particle diameter of 0.1 mm or less, a high yield reaction can be achieved at low temperature.

The solvent used in the method for producing the polysilane of the present invention is not particularly limited as long as it is an inert solvent which does not react with an alkali metal such as sodium and can dissolve the dihalosilane. , Aromatic hydrocarbons such as toluene, xylene and benzene, and aliphatic hydrocarbons such as dodecane, heptane, hexane and cyclohexane.

The reaction can be carried out at a temperature between room temperature and the boiling point of the solvent, and the reaction time is not particularly limited. For example, it is selected in the range of 15 minutes to 24 hours.

The quaternary ammonium salt that can be used in the present invention is represented by the general formula (3). In the formula, R ₄ , R ₅ , R ₆ , and R ₇ are an alkyl group having 1 to 20 carbon atoms or a substituted alkyl group, and at least one of them is an alkyl group having 6 to 20 carbon atoms or a substituted alkyl group, X represents a chlorine, bromine or iodine atom.

When all the alkyl groups of the quaternary ammonium salt have less than 6 carbon atoms, the resulting polysilane has a small effect of improving the molecular weight, which is not preferable. When the number of carbon atoms exceeds 20, the solubility of the quaternary ammonium salt decreases, which is not preferable.

The concentration of the quaternary ammonium salt is preferably 0.1 mmol% or more with respect to the dihalosilane monomer,
More preferably, it is 0.3 mmol% or more. When the concentration of the quaternary ammonium salt is 0.1 mmol% or less, the effect of improving the molecular weight is small, which is not preferable.

Hereinafter, the present invention will be described in more detail by way of examples, but the examples do not limit the present invention.

Example 1 A 100 ml two-necked flask was dried at 200 ° C., and while it was hot, a rubber septum and a three-way cock were attached, and it was cooled while sucking in vacuum. The flask was filled with dry argon, and 1.4 g of metallic sodium lumps cut out in a dry nitrogen atmosphere and 15 ml of toluene dried over sodium and distilled immediately before were added. The flask was set in an ultrasonic disperser (Branson Model 450) under a dry argon flow,
Ultrasonic waves were radiated while heating at 8 ° C to 108 ° C to disperse sodium into particles having an average particle size of 30 µm.

A magnetic stirrer, a rubber septum, and a thermocouple were attached to the flask containing the above sodium suspension.
The temperature was raised to ° C. At the same time as the internal temperature of the flask was stabilized, 0.3 g of phenylmethyldichlorosilane (Shin-Etsu Chemical LS-1490) distilled on calcium hydride was added dropwise using a gas tight syringe, and then tetradodecyl ammonium bromide (prepared separately) Aldrich) 0.1g
2 ml of a dry toluene solution of was added. Further, 4.8 g of phenylmethyldichlorosilane was added dropwise over about 11 minutes. The temperature in the flask was temporarily 110 due to the reaction at the time of dropping.
The temperature rose to 0 ° C., and reflux of the solvent was observed. Upon completion of the dropping, the temperature of the flask was raised to 85 ° C., and the reaction was carried out for 1 hour after starting the dropping.

After completion of the reaction, 35 ml of toluene and 3 ml of isopropyl alcohol were added to the flask under a flow of argon to deactivate the excess metallic sodium, and about 10 ml of distilled water was added to dissolve the sodium chloride precipitate. After the toluene phase was separated and dried over anhydrous magnesium sulfate, the solvent was distilled off to obtain a waxy crude polysilane.
The obtained crude polysilane was subjected to gel permeation chromatography (Waters Maxima-820, column Ultras.
tyragel Linear: Based on mobile phase tetrahydrofuran.
Hereinafter, it may be referred to as GPC) to measure the molecular weight distribution. This is shown in FIG.

Further, this crude polysilane was dissolved in 25 g of tetrahydrofuran and reprecipitated and purified with 150 ml of isopropyl alcohol. The yield, weight average molecular weight, number average molecular weight and dispersity of the obtained polysilane are shown. The dispersity is defined as the ratio of (weight average molecular weight / number average molecular weight), and the smaller the dispersity, the narrower the molecular weight distribution.

Polysilane yield: 43% (1.4 g) Weight average molecular weight: 32,000 Number average molecular weight:
5,000 Dispersity: 6.4

Comparative Example 1 In the same manner as in Example 1, 1.3 g of metallic sodium was dispersed in 19 ml of dry toluene to have an average particle size of about 30 μm.
A magnetic stirrer, a rubber septum, and a thermocouple were attached to this flask, the temperature was raised to 62 ° C., 5.0 g of phenylmethyldichlorosilane was added dropwise using a gas-tight syringe in about 20 minutes, and the reaction was started for 1 hour after the start of addition. Was done. After completion of the reaction, crude polysilane was separated in the same manner as in Example 1 and the molecular weight distribution was measured. This is shown in FIG. Further, similarly, polysilane was reprecipitated and purified. The yield, weight average molecular weight, number average molecular weight and dispersity of the obtained polysilane are shown.

Polysilane yield: 24% (0.8 g) Weight average molecular weight: 230,000 Number average molecular weight: 6,000 Dispersity: 38.3

[0035]

Industrial Applicability According to the production method of the present invention, a high weight average molecular weight of about 5,000 or more, which is useful for photoconductive materials, nonlinear optical materials, precursor materials of non-oxide ceramics having excellent heat resistance, and the like. Polysilane having a high molecular weight and a narrow molecular weight distribution can be obtained in high yield.

[Brief description of drawings]

1 shows the molecular weight distributions of polysilanes of Example 1 and Comparative Example 1. FIG.

Claims (2)

[Claims] 1. A compound represented by the general formula (1) or (2): Embedded image (In these formulas, R ₁ and R ₂ are an alkyl group having 1 to 22 carbon atoms, a substituted alkyl group, an alkoxy group or a substituted alkoxy group, an aryl group having 6 to 22 carbon atoms, a substituted aryl group, an aryloxy group or a substituted aryloxy group. Shows the group
R ₁ and R ₂ may be the same or different from each other,
The arrangement of R ₁ and R ₂ may have a specific regularity. R ₃ represents a bifunctional organic group having 1 to 22 carbon atoms,
Each X independently represents chlorine, bromine or iodine atom.
a, b, and m show the integer of 1-50. A dihalosilane represented by the general formula (3): (In the formula, R ₄ , R ₅ , R ₆ , and R ₇ are an alkyl group having 1 to 20 carbon atoms or a substituted alkyl group, and at least one of them is an alkyl group having 6 to 20 carbon atoms or a substituted alkyl group. , X represents chlorine, bromine or iodine atom), and polycondensation with an alkali metal is carried out in a solvent containing a quaternary ammonium salt represented by the formula (4). 2. The method for producing polysilane according to claim 1, wherein the alkali metal is used in a state of being dispersed in fine particles.