High-molecular-weight polysilane and method for producing same

Abstract

There is provided a highly conductive and good silicon thin film which is obtained by applying a coating-type polysilane composition prepared by use of a polysilane having a large weight average molecular weight to a substrate, followed by baking. A polysilane having a weight average molecular weight of 5,000 to 8,000. The polysilane may be a polymer of cyclopentasilane. A silicon film obtained by applying a polysilane composition in which the polysilane is dissolved in a solvent to a substrate, and baking the substrate at 100 C. to 425 C. The cyclopentasilane may be polymerized in the presence of a palladium catalyst supported on a polymer. The palladium catalyst supported on a polymer may be a catalyst in which palladium as a catalyst component is immobilized on a functional polystyrene. The palladium may be a palladium compound or a palladium complex. The palladium-immobilized catalyst may be formed by microencapsulating a zero-valent palladium complex or a divalent palladium compound with a functional polystyrene. The zero-valent palladium complex may be a tetrakis(triphenylphosphine)palladium (0) complex.

Claims

1. A method for producing a polymer of cyclopentasilane, comprising polymerizing the cyclopentasilane in the presence of a palladium catalyst comprises a zero-valent palladium complex or a divalent palladium compound microencapsulated with functional polystyrene.

2. The method according to claim 1, wherein the palladium catalyst microencapsulated with the functional polystyrene comprises the divalent palladium compound bonded to the functional polystyrene.

3. The method according to claim 1, wherein the functional polystyrene comprises a polystyrene having a polyethylene oxide group with a hydroxy group at a terminal thereof or a polystyrene having a diphenylphosphino group.

4. The method according to claim 1, wherein the method further comprises: reacting a cyclic silane of Formula (1):
(SiR.sup.1R.sup.2).sub.n(1) wherein R.sup.1 and R.sup.2 are each a hydrogen atom, a C.sub.1-6 alkyl group, or a substituted or unsubstituted phenyl group (provided that both R.sup.1 and R.sup.2 are not simultaneously hydrogen atoms), and n is an integer of 4 to 6, with a hydrogen halide in an organic solvent in a presence of an aluminum halide to obtain a cyclic silane of Formula (2):
(SiR.sup.3R.sup.4).sub.n(2) wherein R.sup.3 and R.sup.4 are each a halogen atom, and n is an integer of 4 to 6, and reducing the cyclic silane of Formula (2) with hydrogen or lithium aluminum hydride to obtain a cyclic silane of Formula (3):
(SiH.sub.2).sub.n(3) wherein n is an integer of 4 to 6, and the cyclic silane of Formula (3) includes the cyclopentasilane.

5. The method according to claim 4, wherein both R.sup.1 and R.sup.2 are phenyl groups.

6. The method according to claim 4, wherein both R.sup.3 and R.sup.4 are chlorine atoms.

7. The method according to claim 4, wherein the cyclic silane of Formula (3) contains the cyclopentasilane in an amount of 80% or more by moles.

8. The method according to claim 1, wherein the palladium catalyst comprises the zero-valent palladium complex.

9. The method according to claim 8, wherein the zero-valent palladium complex is a tetrakis(triphenylphosphine)palladium (0) complex.

10. A method for producing a polymer of cyclopentasilane, comprising polymerizing the cyclopentasilane in the presence of a palladium catalyst supported on a polystyrene having a polyethylene oxide group with a hydroxy group at a terminal thereof or a polystyrene having a diphenylphosphino group.

11. The method according to claim 10, wherein the palladium catalyst comprises a divalent palladium compound.

12. The method according to claim 10, wherein the palladium catalyst comprises a zero-valent palladium complex.

13. The method according to claim 12, wherein the zero-valent palladium complex is a tetrakis(triphenylphosphine)palladium (0) complex.

14. A method for producing a polymer of cyclopentasilane, comprising: reacting a cyclic silane of Formula (1):
(SiR.sup.1R.sup.2).sub.n(1) wherein R.sup.1 and R.sup.2 are each a hydrogen atom, a C.sub.1-6 alkyl group, or a substituted or unsubstituted phenyl group (provided that both R.sup.1 and R.sup.2 are not simultaneously hydrogen atoms), and n is an integer of 4 to 6, with a hydrogen halide in an organic solvent in a presence of an aluminum halide to obtain a cyclic silane of Formula (2):
(SiR.sup.3R.sup.4).sub.n(2) wherein R.sup.3 and R.sup.4 are each a halogen atom, and n is an integer of 4 to 6; reducing the cyclic silane of Formula (2) with hydrogen or lithium aluminum hydride to obtain a cyclic silane of Formula (3):
(SiH.sub.2).sub.n(3) wherein n is an integer of 4 to 6; and polymerizing the cyclic silane of Formula (3) in the presence of a palladium catalyst supported on a polymer, wherein the cyclic silane of Formula (3) includes the cyclopentasilane.

15. The method according to claim 14, wherein both R.sup.1 and R.sup.2 are phenyl groups.

16. The method according to claim 15, wherein both R.sup.3 and R.sup.4 are chlorine atoms.

17. The method according to claim 14, wherein the cyclic silane of Formula (3) contains the cyclopentasilane in an amount of 80% or more by moles.

18. The method according to claim 14, wherein the functional polystyrene comprises a polystyrene having a polyethylene oxide group with a hydroxy group at a terminal thereof or a polystyrene having a diphenylphosphino group.

19. The method according to claim 18, wherein the palladium catalyst comprises a divalent palladium compound.

20. The method according to claim 18, wherein the palladium catalyst comprises a zero-valent palladium compound.

Description

EXAMPLES

Example 1 (Synthesis of Polycyclopentasilane by Polymerization of Cyclopentasilane Using Palladium Catalyst Supported on Polymer)

(1) Cyclopentasilane (0.8 g) was placed in a glass sample tube that contained 0.44% by mole of commercially available polymer-supported palladium catalyst (available from Wako Pure Chemical Industries, Ltd., trade name PIPd (Pd content: 3% by mass), 82.1 mg) under an inert atmosphere. The sample tube was loosely capped. In the sample tube, the reaction mixture was stirred for 1 hour. The reaction was then terminated with 5.14 g of cyclohexane. An insoluble component was sedimented, and the mixture was then filtered through a membrane filter made of polytetrafloroethylene with a pore diameter of 0.45 m. Subsequently, the solution was placed in a recovery flask, and a pressure was reduced (about 20 Torr or less, for example, 1 to 20 Torr) to remove a volatile component. The product can be stored as an 8% by mass solution in which the product is dissolved in distilled cyclooctane. The product was measured by gel permeation chromatography. Mn was 4,488 and Mw was 6,454. The amount of residue cyclopentasilane that remained without polymerization was 15.2% by mass.

Comparative Example 1 (Synthesis of Polycyclopentasilane by Polymerization of Cyclopentasilane Using Hydrotalcite-Supported Palladium Catalyst)

(2) Cyclopentasilane (0.75 g) was placed in a glass sample tube that contained 0.88% by mole of commercially available hydrotalcite-supported palladium catalyst (available from Wako Pure Chemical Industries, Ltd., Pd content: 1.5% by mass, 311.0 mg) under an inert atmosphere. The sample tube was loosely capped. In the sample tube, the reaction mixture was stirred for about 20 hours. The reaction was then terminated with 7.68 g of cyclohexane. An insoluble component was sedimented, and the mixture was then filtered through a membrane filter made of polytetrafloroethylene with a pore diameter of 0.45 m. Subsequently, the solution was placed in a recovery flask, and a pressure was reduced (about 20 Tott or less) to remove a volatile component. The product was measured by gel permeation chromatography. Mn was 2,068 and Mw was 3,684. The amount of residue cyclopentasilane that remained without polymerization was 18.9% by mass.

Comparative Example 2 (Synthesis of Polycyclopentasilane by Polymerization of Cyclopentasilane Using Palladium Catalyst Supported on Carbon)

(3) Cyclopentasilane (1.0 g) was placed in a glass sample tube that contained 0.44% by mole of commercially available Pd/C (available from EVONIK, Pd content: 5.0% by mass, 62.1 mg) under an inert atmosphere. The sample tube was loosely capped. In the sample tube, the reaction mixture was stirred for 5 hours. The product after 5 hours was measured by gel permeation chromatography. Mn was 2,844 and Mw was 5,299. The amount of residue cyclopentasilane that remained without polymerization was 60.0% by mass.

Comparative Example 3 (Synthesis of Polycyclopentasilane by Polymerization of Cyclopentasilane Using Platinum Black Catalyst)

(4) Cyclopentasilane (0.8 g) was placed in a glass sample tube that contained 0.44% by mole of commercially available platinum black catalyst (available from Wako Pure Chemical Industries, Ltd., 4.0 mg) under an inert atmosphere. The sample tube was loosely capped. In the sample tube, the reaction mixture was stirred for 6 hours. The reaction was then terminated with 4.51 g of cyclohexane. An insoluble component was sedimented, and the mixture was then filtered through a membrane filter made of polytetrafloroethylene with a pore diameter of 0.45 m. Subsequently, the solution was placed in a recovery flask, and a pressure was reduced (about 20 Torr or less) to remove a volatile component. The product can be stored as a 13.5% by mass solution in which the product is dissolved in distilled cyclohexane. The product was measured by gel permeation chromatography. Mn was 1,117 and Mw was 1,396. The amount of residue cyclopentasilane that remained without polymerization was 15.6% by mass.

INDUSTRIAL APPLICABILITY

(5) A highly conductive and good silicon thin film can be produced on a substrate by forming a coating-type polysilane composition using the polysilane having a large weight average molecular weight of the present invention, and applying the composition to the substrate, followed by baking.