Structure of Microphase-Separated Silica/Siloxane Molecular Composites


The structure of several classes of silica/siloxane molecular composites is investigated using small-angle x-ray and neutron scattering. These filled elastomers can be prepared through different synthethic protocols leading to a range of fillers including particulates with both rough and smooth surfaces, particulates with dispersed interfaces, and polymeric networks. We also find examples of bicontinuous filler phases that we attribute to phase separation via spinodal decomposition. In-situ kinetic studies of particulate fillers show that the precipitate does not develop by conventional nucleation-and-growth. We see no evidence of growth by ripening whereby large particles grow by consumption of small particles. Rather, there appears to be a limiting size set by the elastomer network itself. Phase separation develops by continuous nucleation of particles and subsequent growth to the limiting size. We also briefly report studies of polymer-toughened glasses. In this case, we find no obvious correlation between organic content and structure.

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  1. 1.

    J. E. Mark and D. W. Schaefer in Polymer-Based Molecular Composites, edited by D. W. Schaefer and J. E. Mark (Mat. Res. Soc. Symp. Proc. 171, Pittsburgh, PA 1990).

  2. 2.

    D. W. Schaefer, Science 243, 1023 (1989).

    CAS  Article  Google Scholar 

  3. 3.

    D. W. Schaefer, J. E. Mark, L. Jian, C.-C. Sun, D. McCarthy, C.-Y. Jiang, Y.-P. Ning and S. Spooner, in Ultrastructure Processing of Ceramics. Glasses and Composites, edited by D. R. Uhlman, D. R.Ulrich and S. H. Risbut (J. Wiley, N. Y., 1990) .

  4. 4.

    B. B. Mandelbrot, The Fractal Geometry of Nature (Freeman, San Francisco, 1982).

  5. 5.

    J. E. Martin and A. J. Hurd, J. Appl. Cryst. 20, 61 (1987).

    CAS  Article  Google Scholar 

  6. 6.

    D. W. Schaefer, Bull. Mat. Res. Soc. 13 (2), 22 (1988).

    CAS  Article  Google Scholar 

  7. 7.

    A. Chakrabarti, A. Toral, J. D. Gunton and M. Muthukumar, Phys. Rev. Lett, 63, 2071 (1989).

    Google Scholar 

  8. 8.

    W. Haller and P. B. Macedo, Physics Chem. Glasses 9, 153 (1968).

    CAS  Google Scholar 

  9. 9.

    J. W. Cahn, J. Chem. Phys. 42, 93 (1965).

    CAS  Article  Google Scholar 

  10. 10.

    W. Ruland, J. Appl. Cryst. 4, 70 (1971).

    Article  Google Scholar 

  11. 11.

    J. T. Koberstein, B. Morra and R. S. Stein, J. Appl. Cryst. 13, 34 (1980).

    CAS  Article  Google Scholar 

  12. 12.

    A. J. Hurd, D. W. Schaefer and A. M. Glines, J. Appl. Cryst. 21., 864 (1988).

  13. 13.

    A. Guinier and G. Foumet, Small-Angle Scattering of X-Rays (Available from University Microfilms International, Ann Arbor, MI, 1955).

  14. 14.

    H. D. Bale and P. W. Schmidt, Phys. Rev. Lett. 53, 596 (1984).

    CAS  Article  Google Scholar 

  15. 15.

    K. D. Keefer and D. W. Schaefer, Phys. Rev. Lett. 56, 2376 (1986).

    CAS  Article  Google Scholar 

  16. 16.

    L. R. Gilliom, D. W. Schaefer and J. E. Mark in Polymer-Based Molecular Composites, edited by D. W. Schaefer and J. E. Mark (Mat. Res. Symp. Proc. 171, Pittsburgh, PA 1990).

  17. 17.

    G. L. Wilkes, A. B. Brennan, H. Huang, D. Rodrigues and B. Wang in Polymer Based Molecular Composites, edited by D. W. Schaefer and J. E. Mark (Mat. Res. Soc. Symp. Proc. 171, Pittsburg, PA 1990).

  18. 18.

    P. G. deGennes, Scaling Concepts in Polymer Physics (Cornell University Press, Ithaca, NY, 1979).

  19. 19.

    N. F. Berk, Phys. Rev. Lett. 22, 2718 (1987).

    Article  Google Scholar 

  20. 20.

    J. E. Mark and C.-C. Sun, Polym. Bull. 18, 259 (1987).

    CAS  Article  Google Scholar 

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Correspondence to Dale W. Schaefer.

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Schaefer, D.W., Mark, J.E., Mccarthy, D. et al. Structure of Microphase-Separated Silica/Siloxane Molecular Composites. MRS Online Proceedings Library 171, 57–63 (1989).

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