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Journal for Biophysical Chemistry

Confinement and compression of an oligomer brush

Abstract

Self-assembled monolayers and oligomer brushes confined between two parallel plates show compressional forces that are nonmonotonic as a function of plate separation. In a realistic model of short alkanethiols, based on the rotationally isomeric state model with parameters from ab initio calculations, the authors show that nonmonotonic forces arise from the elimination of longer conformers as the distance between the plates is reduced. This nonmonotonicity is a size effect that disappears when the length of the polymer molecule is sufficiently increased. An analytical model is developed that allows experimentalists to extract energy-averaged brush height distributions from compressional force curves.

References

  1. R. R. Netz and D. Andelman, Phys. Rep. 380, 1 (2003).

    Article  CAS  Google Scholar 

  2. K. L. Prime and G. M. Whitesides, J. Am. Chem. Soc. 115, 10714 (1993).

    Article  CAS  Google Scholar 

  3. J. Satulovsky, M. A. Carignano, and I. Szleifer, Proc. Natl. Acad. Sci. U.S.A. 97, 9037 (2000).

    Article  CAS  Google Scholar 

  4. Y.-Y. Luk, M. Kato, and M. Mrksich, Langmuir 16, 9604 (2000).

    Article  CAS  Google Scholar 

  5. R. E. Holmlin, X. Chen, R. G. Chapman, S. Takayama, and G. M. Whitesides, Langmuir 17, 2841 (2001).

    Article  CAS  Google Scholar 

  6. S. Herrwerth, W. Eck, S. Reinhardt, and M. Grunze, J. Am. Chem. Soc. 125, 9359 (2003).

    Article  CAS  Google Scholar 

  7. J. Groll, Z. Ademovic, T. Ameringer, D. Klee, and M. Moeller, Biomacromolecules 6, 956 (2005).

    Article  CAS  Google Scholar 

  8. S. Alexander, J. Phys. 38, 983 (1977).

    Article  CAS  Google Scholar 

  9. P. G. de Gennes, Macromolecules 13, 1069 (1980).

    Article  Google Scholar 

  10. S. T. Milner, T. A. Witten, and M. E. Cates, Macromolecules 21, 2610 (1988).

    Article  CAS  Google Scholar 

  11. R. R. Netz and M. Schick, Macromolecules 31, 5105 (1998).

    Article  CAS  Google Scholar 

  12. R. R. Netz and M. Schick, Europhys. Lett. 38, 37 (1997).

    Article  CAS  Google Scholar 

  13. M. Murat and G. S. Grest, Macromolecules 22, 4054 (1989).

    Article  CAS  Google Scholar 

  14. M. P. Pépin and M. D. Whitmore, J. Chem. Phys. 111, 10381 (1999).

    Article  Google Scholar 

  15. E. P. K. Currie, G. J. Fleer, M. A. Cohen Stuart, and O. V. Borisov, Eur. Phys. J. E 1, 27 (2000).

    Article  CAS  Google Scholar 

  16. C. Seidel and R. R. Netz, Macromolecules 33, 634 (2000).

    Article  CAS  Google Scholar 

  17. M. A. Carignano and I. Szleifer, Mol. Phys. 100, 2993 (2002).

    Article  CAS  Google Scholar 

  18. L. Livadaru and H. J. Kreuzer, Z. Phys. Chem. 218, 929 (2004).

    Article  CAS  Google Scholar 

  19. G. Oncins, C. Vericat, and F. Sanz, J. Chem. Phys. 128, 044701 (2008).

    Article  Google Scholar 

  20. M. Heuberger, T. Drobek, and N. D. Spencer, Biophys. J. 88, 495 (2005).

    Article  CAS  Google Scholar 

  21. L. L. Cai and S. Granick, Adv. Colloid Interface Sci. 94, 135 (2001).

    Article  CAS  Google Scholar 

  22. T. W. Kelley, P. A. Schorr, K. D. Johnson, M. Tirrell, and C. D. Frisbie, Macromolecules 31, 4297 (1998).

    Article  CAS  Google Scholar 

  23. C. S. Hodges, Adv. Colloid Interface Sci. 99, 13 (2002).

    Article  CAS  Google Scholar 

  24. P. T. Mikulski and J. A. Harrison, J. Am. Chem. Soc. 123, 6873 (2001).

    Article  CAS  Google Scholar 

  25. M. Salmeron, Tribol. Lett. 10, 69 (2001).

    Article  CAS  Google Scholar 

  26. K. Ohno, T. Sakamoto, T. Minagawa, and Y. Okabe, Macromolecules 40, 723 (2007).

    Article  CAS  Google Scholar 

  27. F. S. Csajka, R. R. Netz, C. Seidel, and J. F. Joanny, Eur. Phys. J. E 4, 505 (2001).

    Article  CAS  Google Scholar 

  28. M. A. Carignano and I. Szleifer, Macromolecules 28, 3197 (1995).

    Article  CAS  Google Scholar 

  29. A. E. van Giessen and I. Szleifer, J. Chem. Phys. 102, 9069 (1995).

    Article  Google Scholar 

  30. O. J. Hehmeyer, G. Arya, A. Z. Panagiotopoulos, and I. Szleifer, J. Chem. Phys. 126, 244902 (2007).

    Article  Google Scholar 

  31. L. Livadaru, R. R. Netz, and H. J. Kreuzer, J. Chem. Phys. 118, 1404 (2003).

    Article  CAS  Google Scholar 

  32. J. B. Klauda, B. R. Brooks, A. D. J. MacKerell, R. M. Venable, and R. W. Pastor, J. Phys. Chem. B 109, 5300 (2005).

    Article  CAS  Google Scholar 

  33. J. I. Siepmann and D. Frenkel, Mol. Phys. 75, 59 (1992).

    Article  CAS  Google Scholar 

  34. J. I. Siepmann and I. R. McDonald, Phys. Rev. Lett. 70, 453 (1993).

    Article  CAS  Google Scholar 

  35. D. B. Staple, F. Hanke, and H. J. Kreuzer, New J. Phys. 9, 68 (2007).

    Article  Google Scholar 

  36. For example, peaks in the density of states are still visible in situations where many states are accessible, such that distributions appear otherwise smooth, see Ref. 35. D. B. Staple, F. Hanke, and H. J. Kreuzer, New J. Phys. 9, 68 (2007).

    Article  Google Scholar 

  37. In the energy versus height plot of the conformers, there are lines or bands of equal energy. Their origin is simple: introducing a gauche state in an all-trans conformer costs 23 meV according to Table I, independent of where along the chain it is introduced, but resulting in different heights. The next band has two gauche states and the next after that has a gauche defect (ttg−g+tt), etc.

  38. If the density is a series of delta-functions D(h) = Σa i δ(hh i, as it would be if only a small number of distinct conformers contribute to the brush, we get steps in the free energy and spikes on the force/pressure curve.

  39. G. Oncins (private communication).

  40. R. L. C. Wang, H. J. Kreuzer, and M. Grunze, Phys. Chem. Chem. Phys. 2, 3613 (2000).

    Article  CAS  Google Scholar 

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Foster, S., Wainwright, C., Staple, D.B. et al. Confinement and compression of an oligomer brush. Biointerphases 5, 69–73 (2010). https://doi.org/10.1116/1.3455152

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  • DOI: https://doi.org/10.1116/1.3455152