Liquid lenses at fluid/fluid interfaces

(Note: The full text of this document is currently only available in the PDF Version )

Robert Aveyard and John H. Clint


Abstract

In a previous study we have explored how the wettability of a spherical solid particle resting in a fluid/fluid interface can be influenced by effects of line tension (τ) acting in the circular three-phase contact line around the particle. Here, we extend that study to consider possible effects of line tension on a small liquid lens resting in a liquid surface; the deformability of the lens predictably adds some new features. In the case of a lens we are interested in the way in which τ influences both the complete wetting of the subphase by the lens and the complete wetting of the lens by the subphase (i.e. engulfment of the lens). We propose a definition of a spreading coefficient (for the lens material on the subphase) which incorporates line tension. Negative τ favours spreading and it is shown that it is possible in systems in which large lenses would not spread (e.g. dodecane on water at room temperature), the operation of negative line tension could cause spreading in lenses below a critical radius. For positive τ the behaviour of a lens broadly mirrors that of a spherical solid particle. For line tensions below a critical value τc the lens can assume a thermodynamically stable configuration in the interface. This happens when the Gibbs energy of the system with the lens at the interface is more negative than that for the system in which the lens exists (in the form of a spherical droplet) in the more wetting of the contiguous phases. For line tensions between τc and τm only metastable configurations are possible; τm is the line tension above which no stable configuration for the lens at the interface is possible. We consider possible effects of line tension in surfactant systems of potential practical interest, and allude to the role of liquid oil droplets in the rupture of thin liquid films and hence in foam breaking.


References

  1. P. R. Garrett, in Defoaming: Theory and Industrial Applications, ed. P. R. Garrett, Marcel Dekker, New York, 1993, p. 1 Search PubMed.
  2. R. Aveyard, P. Cooper, P. D. I. Fletcher and C. E. Rutherford, Langmuir, 1993, 9, 604 CrossRef CAS.
  3. L. Lobo and D. T. Wasan, Langmuir, 1993, 9, 1668 CrossRef CAS.
  4. V. Bergeron, M. E. Fagan and C. J. Radke, Langmuir, 1993, 9, 1704 CrossRef CAS.
  5. A. Scheludko, B. V. Toshev and D. T. Bojadjiev, J. Chem. Soc., Faraday Trans. 1, 1976, 72, 2815 RSC.
  6. A. Scheludko, B. V. Toshev and D. Platikanov, in The Modern Theory of Capillarity ed. R. C. Goodrich and A. I. Rusanov, Akademie-Verlag, Berlin, 1981, p. 163et seq. Search PubMed.
  7. J. Mingins and A. Scheludko, J. Chem. Soc., Faraday Trans. 1, 1979, 75, 1 RSC.
  8. R. Aveyard and J. H. Clint, J. Chem. Soc., Faraday Trans., 1996, 92, 85 RSC.
  9. R. Aveyard, B. D. Beake and J. H. Clint, J. Chem. Soc., Faraday Trans., 1996, 92, 4271 RSC.
  10. B. Widom, J. Phys. Chem., 1995, 99, 2803 CrossRef CAS.
  11. P. R. Pujado and L. E. Scriven, J. Colloid Interface Sci., 1972, 40, 82 CrossRef CAS.
  12. J. S. Rowlinson and B. Widom, Molecular Theory of Capillarity, Oxford University Press, Oxford, 1989, ch. 8 Search PubMed.
  13. J. A. Wallace and S. Schurch, J. Colloid Interface Sci., 1988, 124, 452 CrossRef CAS.
  14. V. Retter and D. Vollhardt, Langmuir, 1993, 9, 2478 CrossRef CAS.
  15. R. Aveyard and J. H. Clint, J. Chem. Soc., Faraday Trans., 1995, 91, 2681 RSC.
  16. P. R. Garrett, J. Colloid Interface Sci., 1980, 76, 587 CrossRef CAS.
  17. R. E. Johnson and R. H. Dettre, J. Colloid Interface Sci., 1966, 21, 610 CAS.
  18. T. G. Peck, Ph.D. Thesis, University of Hull, 1994.
  19. L.-J. Chen, M.-C. Hsu, S.-T. Lin and S.-Y. Yang, J. Phys. Chem., 1995, 99, 4687 CrossRef CAS.
Click here to see how this site uses Cookies. View our privacy policy here.