Issue |
Europhys. Lett.
Volume 56, Number 5, December 2001
|
|
---|---|---|
Page(s) | 695 - 701 | |
Section | Condensed matter: structure, mechanical and thermal properties | |
DOI | https://doi.org/10.1209/epl/i2001-00576-1 | |
Published online | 01 December 2003 |
Wetting behavior of nanodroplets: The limits of Young's rule validity
Institute of Physical Chemistry, Bulgarian Academy of Sciences
G. Bonchev Str. Block 11, 1113 Sofia, Bulgaria
Received:
14
May
2001
Accepted:
6
September
2001
We study the contact angle of polymer melt sessile droplets on a flat
structureless substrate subject to long-range van der Waals forces when the
droplet size is diminished. For this purpose, droplets containing 4096 to
512 monomers for chains of length N=32 are carefully equilibrated at
of the Θ-temperature using a coarse-grained bead spring model of
flexible polymers in a Monte Carlo computer experiment. The spherically
averaged density profile of these droplets, both in the z-direction
perpendicular to the substrate surface and in the radial direction, is
obtained. At weak adhesion we find that the contact angle grows steadily
with the decrease of drop size so that below a critical size these drops
dewet the surface. This suggests a strong contribution of a positive line
tension
in the determination of the equilibrium drop shape. At
much stronger adhesion, however, the contact angle does not change with drop
size, indicating
In general, our simulational results
outline the limits of validity of Young's relation for the contact angle of
sessile nanodroplets and support the more general Gretz rule which takes
into account the role of line tension in the balance of surface forces.
PACS: 68.08.Bc – Wetting / 68.08.-p – Liquid-solid interfaces / 61.25.Hq – Macromolecular and polymer solutions; polymer melts; swelling
© EDP Sciences, 2001
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