Claims
- 1. A method of preparing a first polysilane, containing at least one weight percent vinyl, having the general formula
- [RSi][R.sub.2 Si]
- where there are present 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units or having the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where the remaining bonds on silicon are attached to other silicon atoms and vinyl groups, said method consisting of reacting under anhydrous conditions in the presence of a solvent a second polysilane of general formula
- [RSi][R.sub.2 Si]
- where there are present 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units or of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where the remaining bonds on silicon are attached to other silicon atoms and chlorine or bromine atoms with vinyl Grignard reagent or vinyllithium, at a temperature of 0.degree. to 120.degree. C. and thereafter removing the solvent at a temperature of less than about 200.degree. C. to obtain the vinyl-containing first polysilane.
- 2. A method as defined in claim 1 wherein the remaining bonds on silicon in the second polysilane are attached to other silicon atoms and chlorine atoms; and where R in both the first and second polysilanes is a methyl group.
- 3. A method as defined in claim 2 where the solvent is removed at a temperature of less than 160.degree. C.
- 4. A method as defined in claim 2 wherein the second polysilane is reacted with a vinyl Grignard reagent.
- 5. A method as defined in claim 4 where the solvent is removed at a temperature of less than 160.degree. C.
- 6. A method as defined in claim 2 wherein the second polysilane is reacted with vinyllithium.
- 7. A method as defined in claim 6 where the solvent is removed at a temperature of less than 160.degree. C.
- 8. A method as defined in claim 1 wherein the first polysilane and the second polysilane have the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 40 to 99 mole percent [RSi] units, and 1 to 30 mole percent [R"Si] units.
- 9. A method as defined in claim 8 where there is present in the first polysilane and the second polysilane 1 to 10 mole percent [R.sub.2 Si] units, 80 to 99 mole percent [RSi] units, and 1 to 20 mole percent [R"Si] units.
- 10. A method of preparing a first polysilane, containing at least one weight percent vinyl, having the general formula
- [RSi][R.sub.2 Si]
- where there are present 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units or having the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where the remaining bonds on silicon are attached to other silicon atoms, vinyl groups, and R' radicals where R' is an alkyl radical containing 1 to 8 carbon atoms or phenyl radical, said method consisting of reacting under anhydrous conditions in the presence of a solvent a second polysilane of general formula
- [RSi][R.sub.2 Si]
- where there are present 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units or of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1, and where the remaining bonds on silicon are attached to other silicon atoms and chlorine or bromine atoms with a mixture selected from the group consisting of (1) a vinyl Grignard reagent and an organo Grignard reagent of general formula R'MgX', (2) a vinyl Grignard reagent and an organolithium compound of general formula R'Li, (3) vinyllithium and organo Grignard reagent of general formula R'MgX', and (4) vinyllithium and an organolithium compound of general formula R'Li where in the mixture R' is an alkyl radical containing 1 to 8 carbon atoms or a phenyl radical and X' is chlorine, bromine, or iodine, at a temperature of 0.degree. to 120.degree. C. and thereafter removing the solvent at a temperature of less than about 200.degree. C. to obtain the vinyl-containing first polysilane.
- 11. A method as defined in claim 10 where the vinyl/R' molar ratio in the mixture is less than about 2.0.
- 12. A method as defined in claim 11 where the vinyl/R' molar ratio in the mixture is less than about 1.5.
- 13. A method as defined in claim 12 wherein the remaining bonds on silicon in the second polysilane are attached to other silicon atoms and chlorine atoms; where R in both the first and second polysilanes is a methyl group; and where R' is a methyl group.
- 14. A method as defined in claim 13 where the solvent is removed at a temperature of less than 160.degree. C.; and where the molar ratio of vinyl/methyl in the mixture is less than about 1.0.
- 15. A method as defined in claim 14 where the mixture contains a vinyl Grignard reagent and an organo Grignard reagent of general formula CH.sub.3 MgX'.
- 16. A method as defined in claim 14 where the mixture contains a vinyl Grignard reagent and methyllithium.
- 17. A method as defined in claim 14 where the mixture contains vinyllithium and organo Grignard reagent of general formula CH.sub.3 MgX'.
- 18. A method as defined in claim 14 where the mixture contains vinyllithium and methyllithium.
- 19. A method as defined in claim 10 where the first polysilane contains 2 to 5 weight percent vinyl.
- 20. A method as defined in claim 10 wherein the first polysilane and the second polysilane have the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 40 to 99 mole percent [RSi] units, and 1 to 30 mole percent [R"Si] units.
- 21. A method as defined in claim 20 where there is present in the first polysilane and the second polysilane 1 to 10 mole percent [R.sub.2 Si] units, 80 to 99 mole percent [RSi] units, and 1 to 20 mole percent [R"Si] units.
- 22. A first polysilane as prepared by the method of claim 1.
- 23. A first polysilane as prepared by the method of claim 3.
- 24. A first polysilane as prepared by the method of claim 5.
- 25. A first polysilane as prepared by the method of claim 9.
- 26. A first polysilane as prepared by the method of claim 10.
- 27. A first polysilane as prepared by the method of claim 14.
- 28. A first polysilane as prepared by the method of claim 15.
- 29. A first polysilane as prepared by the method of claim 19.
- 30. A first polysilane as prepared by the method of claim 20.
- 31. A method of preparing a silicon carbide-containing ceramic article, said method comprising (A) forming an article of the desired shape from a polysilane, containing at least one weight percent vinyl, of the general formula
- [RSi][R.sub.2 Si]
- in which polysilane there are from 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units or of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1 and where the remaining bonds on silicon are attached to other silicon atoms and vinyl groups; (B) curing the article formed in step (A) so that the article will not melt or fuse during pyrolysis step (C); and (C) heating the cured article of step (B) in an inert atmosphere or in a vacuum to an elevated temperature greater than 800.degree. C. until the polysilane is converted to a silicon carbide-containing ceramic article.
- 32. A method as defined in claim 31 where the article is cured in step (B) by heating the article to about 250.degree. C. at a rate sufficiently slow so that the article does not melt or fuse during the curing step.
- 33. A method as defined in claim 32 where R in the polysilane is a methyl group; and where the curing step (B) is carried out under an inert atmosphere.
- 34. A method as defined in claim 33 wherein steps (B) and (C) are combined into a single step whereby the article of step (A) is thermally cured during the initial stages of the pyrolysis step (C).
- 35. A method as defined in claim 34 where the polysilane contains 2 to 5 weight percent vinyl.
- 36. A method as defined in claim 31 where the article is cured in step (B) by UV irradiation.
- 37. A method as defined in claim 31 where the polysilane is of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 40 to 99 mole percent [RSi] units, and 1 to 30 mole percent [R"Si] units.
- 38. A method as defined in claim 37 where there is present in the polysilane 1 to 10 mole percent [R.sub.2 Si] units, 80 to 99 mole percent [RSi] units, and 1 to 20 mole percent [R"Si] units.
- 39. A method of preparing a silicon carbide-containing ceramic article, said method comprising (A) forming an article of the desired shape from a polysilane, containing at least one weight percent vinyl, of the general formula
- [RSi][R.sub.2 Si]
- in which polysilane there are from 0 to 60 mole percent [R.sub.2 Si] units and 40 to 100 mole percent [RSi] units, or of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 0.1 to 99.9 mole percent [RSi] units, and 0.1 to 99.9 mole percent [R"Si] units where R is an alkyl radical containing 1 to 8 carbon atoms, R" is selected from the group consisting of alkyl radicals of at least six carbon atoms, phenyl radicals, and radicals of the formula A.sub.y X.sub.(3-y) Si(CH.sub.2).sub.z -- where A is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, y is an integer equal to 0 to 3, X is chlorine or bromine, and z is an integer greater than or equal to 1 and where the remaining bonds on silicon are attached to other silicon atoms, vinyl groups, and R' groups where R' is an alkyl radical containing 1 to 8 carbon atoms or a phenyl radical; (B) curing the article formed in step (A) so that the article will not melt or fuse during pyrolysis step (C); and (C) heating the cured article of step (B) in an inert atmosphere or in a vacuum to an elevated temperature greater than 800.degree. C. until the polysilane is converted to a silicon carbide-containing ceramic article.
- 40. A method as defined in claim 39 where the article is cured in step (B) by heating the article to about 250.degree. C. at a rate sufficiently slow so that the article does not melt or fuse during the curing step.
- 41. A method as defined in claim 40 where the vinyl/R' molar ratio is less than about 2.0 in the polysilane.
- 42. A method as defined in claim 41 where the vinyl/R' molar ratio is less than about 1.5 in the polysilane.
- 43. A method as defined in claim 42 where R and R' are both methyl groups; where the vinyl/R' molar ratio is less than about 1.0; and where the curing step (B) is carried out under an inert atmosphere.
- 44. A method as defined in claim 42 wherein steps (B) and (C) are combined into a single step whereby the article of step (A) is thermally cured during the initial stages of the pyrolysis step (C).
- 45. A method as defined in claim 43 wherein steps (B) and (C) are combined into a single step whereby the article of step (A) is thermally cured during the initial stages of the pyrolysis step (C).
- 46. A method as defined in claim 44 where the polysilane contains 2 to 5 weight percent vinyl.
- 47. A method as defined in claim 45 where the polysilane contains 2 to 5 weight percent vinyl.
- 48. A method as defined in claim 39 where the article is cured in step (B) by UV irradiation.
- 49. A method as defined in claim 39 where the polysilane is of the general formula
- [RSi][R.sub.2 Si][R"Si]
- where there are present 0 to 40 mole percent [R.sub.2 Si] units, 40 to 99 mole percent [RSi] units, and 1 to 30 mole percent [R"Si] units.
- 50. A method as defined in claim 49 where there is present in the polysilane 1 to 10 mole percent [R.sub.2 Si] units, 80 to 99 mole percent [RSi] units, and 1 to 20 mole percent [R"Si] units.
STATEMENT OF GOVERNMENT RIGHTS
The United States Government has rights in this invention pursuant to Contract Number F33615-83-C-5006 awarded by the United States Air Force.
US Referenced Citations (8)
Non-Patent Literature Citations (2)
Entry |
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