Research on Chemical Intermediates

, Volume 28, Issue 2–3, pp 159–174 | Cite as

Conformational disorder in the propagating radical of dimethacrylate polymers

  • Anna M. Ferretti
  • Giorgio Costante
  • Alessandro Ponti


Photopolymerization of methacrylic monomers yields samples with trapped radicals that are easily detected by electron paramagnetic resonance (EPR) spectroscopy. Despite its simplicity, there is no general agreement about the interpretation of this spectrum, in particular, about the role of methylene β protons. An extensive ENDOR study of the propagating radical in photopolymerized dimethacrylates has been carried out in order to obtain detailed information about methylene hyperfine couplings and, thus, about radical conformation. It is shown that literature models are not able to reproduce the ENDOR results and that only accurate fitting of ENDOR spectra obtained by saturating the EPR spectrum at different positions gives reliable information about radical conformation, thanks to the exploitation of conformational selectivity. It turns out that most radicals are in the minimum energy conformation, but any possible conformation is assumed by non negligible fractions of radical.



Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    G. K. Fraenkel, J. M. Hirshon and C. Walling, J. Am. Chem. Soc. 76, 3606 (1954).Google Scholar
  2. 2.
    R. E. Michel, F. W. Chapman and T. J. Mao, J. Chem. Phys. 45, 4604 (1966).Google Scholar
  3. 3.
    E. E. Schneider, Nature (London) 168, 645 (1951).Google Scholar
  4. 4.
    R. J. Abraham, H. W. Melville, D. W. Ovenall and D. H. Whiffen, Trans. Faraday Soc. 54, 1133 (1958).Google Scholar
  5. 5.
    G. W. Neilson and M. C. R. Symons, J. Chem. Soc. Perkin Trans. 2 397 (1973).Google Scholar
  6. 6.
    P. Kourím and K. Vacek, Trans. Faraday Soc. 61, 415 (1965).Google Scholar
  7. 7.
    C. Heller and H. M. McConnell, J. Chem. Phys. 32, 1535 (1960).Google Scholar
  8. 8.
    M. Iwasaki and Y. Sakai, J. Polym. Sci., Part A-1 (Polym. Chem.) 7, 1537 (1969).Google Scholar
  9. 9.
    M. P. Tonge, R. J. Pace and R. G. Gilbert, Macromol. Chem. Phys. 195, 3159 (1994).Google Scholar
  10. 10.
    M. J. Bowden and J. H. O'Donnell, J. Phys. Chem. 72, 1577 (1968).Google Scholar
  11. 11.
    M. Kamachi, M. Kohno, D. J. Liaw and S. Katsuki, Polym. J. 10, 69 (1978).Google Scholar
  12. 12.
    M. Kamachi, Y. Kuwae, S. Nokazura, K. Hatada and H. Yuki, Polym. J. 13, 919 (1981).Google Scholar
  13. 13.
    M. E. Best and P. H. Kasai, Macromolecules 22, 2622 (1989).Google Scholar
  14. 14.
    Y. Tian, S. Zhu, A. E. Hamielec, D. B. Fulton and D. R. Eaton, Polymer 33, 384 (1992).Google Scholar
  15. 15.
    D. C. Doetschman, R. C. Mehlenbacher and D. Cywar, Macromolecules 29, 1807 (1996).Google Scholar
  16. 16.
    Y. Sugiyama, Bull. Chem. Soc. Jpn. 71, 1019 (1998).Google Scholar
  17. 17.
    Y. Sakai and M. Iwasaki, J. Polym. Sci., Part A-1 (Polym. Chem.) 7, 1749 (1969).Google Scholar
  18. 18.
    E. Selli, C. Oliva and G. Termignone, J. Chem. Soc. Faraday Trans. 90, 1967 (1994).Google Scholar
  19. 19.
    C. Oliva, E. Selli, S. Di Blas and G. Termignone, J. Chem. Soc. Perkin Trans. 2 2133 (1995).Google Scholar
  20. 20.
    E. J. Harbron, V. P. McCaffrey, R. X. Xu and M. D. E. Forbes, J. Am. Chem. Soc. 122, 9182 (2000).Google Scholar
  21. 21.
    M. M. Dorio and J. H. Freed (Eds), Multiple Electron Resonance Spectroscopy. Plenum Press, New York (1979).Google Scholar
  22. 22.
    I. R. Bellobono, C. Oliva, R. Morelli, E. Selli and A. Ponti, J. Chem. Soc.-Faraday Trans. 86, 3273 (1990).Google Scholar
  23. 23.
    C. Oliva, E. Selli, A. Ponti, I. R. Bellobono and R. Morelli, J. Phys. Org. Chem. 5, 55 (1992).Google Scholar
  24. 24.
    F. Szöcs, J. Appl. Polym. Sci. 32, 5673 (1986).Google Scholar
  25. 25.
    L. Brown, T. G. Carswell-Pomerantz, D. J. T. Hill and P. J. Pomery, Radiat. Phys. Chem. 48, 627 (1996).Google Scholar
  26. 26.
    H. Seidel, Z. Phys. 165, 239 (1961).Google Scholar
  27. 27.
    E. Wasserman, L. C. Snyder and W. A. Yager, J. Chem. Phys. 41, 1763 (1964).Google Scholar
  28. 28.
    A. Schweiger and H. H. Günthard, Chem. Phys. 70, 1 (1982).Google Scholar
  29. 29.
    J. A. Nelder and R. Mead, Comput. J. 7, 308 (1965).Google Scholar

Copyright information

© VSP 2002 2002

Authors and Affiliations

  • Anna M. Ferretti
  • Giorgio Costante
  • Alessandro Ponti

There are no affiliations available

Personalised recommendations