Rupture and coarsening pathways for dewetting two-layer films
and films of binary mixtures
by Uwe Thiele
School of Mathematics, Loughborough University Loughborough,
Leicestershire, LE11 3TU, UK
After reviewing recent experiments on dewetting of thin films
we focus on the description of two-layer films of simple liquids
and one-layer films of binary mixtures.
First, we discus the two-layer films and review the structure
of the evolution equations in long wave approximation for closed
and open geometries, i.e. two layers between two solid substrates
[1] and two layers on a solid substrate in a gas atmosphere
[2-4], respectively. Focusing on the latter we present results
regarding the initial film rupture [2] and then embark on a study
of the long-time, i.e. coarsening behaviour in two [3] and three
dimensions [4]. To do so we incorporate long-range van-der-Waals
as well as short-range polar interactions. In particular, we show
that the system may show different linear instability modes.
Dominated either by a varicose or a zigzag mode the film ruptures
at the liquid-gas interface or at the substrate, respectively. A
study of the coarsening behaviour allows to identify different
pathways involving morphological transitions.
Second, we discus the description of films of binary mixtures
such as polymer blends that might decompose and dewet
simultaneously. We introduce model-H coupling transport equations
for momentum and concentration fields completing the description
by boundary conditions at the free surface and the solid
substrate [5]. We discuss the linear stability of homogeneously
mixed and stratified films for energetically neutral and biased
interfaces. We show that stratified films give rise to two
instability modes driven by Marangoni and Korteweg stresses,
respectively [6].
References
D. Merkt, A. Pototsky, M. Bestehorn, and U. Thiele, Phys.
Fluids 17, 064104 (2005)
A. Pototsky, M. Bestehorn, D. Merkt and U. Thiele, Phys. Rev.
E 70, 025201(R) (2004)
A. Pototsky, M. Bestehorn, D. Merkt and U. Thiele, J. Chem.
Phys. 122, 224711 (2005)
A. Pototsky, M. Bestehorn, D. Merkt and U. Thiele, Europhys.
Lett. 74, 665-671 (2006)
U. Thiele, S. Madruga and L. Frastia, Phys. Fluids 19, 122106
(2007)
