Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-27T01:33:34.686Z Has data issue: false hasContentIssue false
  • English
  • Français

Schnell Gel: Rapid Formation of Low Density Gels from a Tetra(Fluoroalkoxy)Silane

Published online by Cambridge University Press:  10 February 2011

Kenneth G. Sharp
Kenneth G. Sharp*
Affiliation:
Central Research, DuPont Co., Wilmington, DE, 19880-0323, U.S.A., [email protected]
Get access

Abstract

A new family of simple precursors to silica gel has been developed. The gel precursors are tetra(polyfluoroalkoxy)silanes, the prototype being Si(OCH2CF3)4. Formation of transparent monolithic gels with no added catalyst can be six orders of magnitude faster than comparable reactions of Si(OCH2CH3)4[TEOS]. Extremely low density gels can be generated in minutes at concentrations at which TEOS does not gel at all. Pore sizes in the wet gels were estimated from hydrodynamic relaxation in a beam-bending experiment on cylindrical logs. In a gel at 1% solids, the pore size was approximately 100 nm. Monolithic gels can be created at concentrations at least as low as 0.1% solids and have higher moduli than predicted. NMR and GC/IR evidence indicates extremely facile hydrolysis and condensation pathways and very few silanol or cyclic intermediates in the sol. The chemistry can also be conducted in perfluorinated solvents, enabling synthesis of silica/fluoropolymer nanocomposites.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 520: Symposium P – Nanostructured Powders & Their Industrial Application , 1998 , 123
Copyright
Copyright © Materials Research Society 1998

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Rabinovich, E. M., Wood, D. L., Materials Research Soc. Better Ceramics through Chemistry II 73, 251 (1986).Google Scholar
2. Schmidt, H., J. Non Cryst. Solids 73, 681–91 (1985).Google Scholar
3. Schmidt, H., Scholze, H., Kaiser, A., J. Non-Cryst. Solids 63, 1–11 (1984).Google Scholar
4. Delattre, L., Babonneau, F., Mater. Res. Soc. Symp. Proc. 346, 365–70 (1994).Google Scholar
5. Perfluoro alcohols such as CF3OH are unstable, decomposing into HF and a perfluoroaldehyde or -ketone; the perfluoroalkyl groups must be separated from the oxygen by at least one methylene group.Google Scholar
6. Hrubesh, L. W., Tillotson, T. M., Poco, J. F., Mater. Res. Soc. Symp. Proc. 180, 315–19 (1990).Google Scholar
7. Tillotson, T. M., Hrubesh, L. W., J. Non-Cryst. Solids 145, 44–50 (1992).Google Scholar
8. Woignier, T., Phalippou, J., J. Non-Cryst. Solids 93, 17–21 (1987).Google Scholar
9. Scherer, G. W., J. Non-Cryst. Solids 142, 18–35 (1992).Google Scholar
10. Scherer, G. W., Faraday Discuss. 101, 225–234 (1995).Google Scholar
11. Brinker, C. J., Scherer, G. W. Sol-gel Science; Academic Press: San Diego, CA, 1990.Google Scholar
12. Brinker, C. J., J. Non-Cryst. Solids 100, 31–50 (1988).Google Scholar
13. Colby, M. W., Osaka, A., Mackenzie, J. D., J. Non-Cryst. Solids 99, 129–39 (1988).Google Scholar
14. Gottardi, V., Guglielmi, M., Bertoluzza, A., Fagnano, C., Morelli, M. A., J. NonCryst. Solids 63, 71–80 (1984).Google Scholar
15. Eaborn, C. Organosilicon Compounds; Butterworth Scientific: London, 1960.Google Scholar
16. Scherer, G. W., J. Non-Cryst. Solids 108, 18–27 (1989).Google Scholar
17. Jones, W. M., Fischbach, D. B., J. Non-cryst. Solids 101, 123 (1988).Google Scholar
18. Acker, E. G., J. Colloid Interface Sci. 32, 41–54 (1970).Google Scholar
19. Kozuka, H., Sakka, S., Chem. Mater. 1, 398–404 (1989).Google Scholar
20. Coltrain, B. K., Melpolder, S. M., Salva, J. M.. “Effect of hydrogen ion concentration on gelation of tetrafunctional silicate sol-gel systems”; Ultrastruct. Process. Adv. Mater., 1992, Int. Conf. Ultrastruct. Process. Ceram., Glasses Compos.Google Scholar
21. Woignier, T., Phalippou, J., Vacher, R., Mater. Res. Soc. Symp. Proc. 121, 697–702 (1988).Google Scholar
22. Fricke, J., Gross, J., Mater. Eng. (N. Y.) 8, 311–36 (1994).Google Scholar
23. Kelts, L. W., Armstrong, N. J., Mater. Res. Soc. Symp. Proc. 121, 519–22 (1988).Google Scholar
24. Silanol-bearing species might not, however, elute from the gas chromatograph.Google Scholar
25. Teflon (polytetrafluoroethylene) itself is virtually insoluble due to its extremely high molecular weight and crystallinity.Google Scholar
26. Sharp, K. G., J. Sol-Gel Sci. Technol. 2, 35–41 (1994).Google Scholar
27. Michalczyk, M. J., Sharp, K. G. and Stewart, C. W., U.S. Patent 5,726,247, issued to the DuPont Co.Google Scholar
28. Haskell Laboratories, DuPont Co.Google Scholar