Regensburg 2002 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 14: organische Schichten
DS 14.4: Vortrag
Mittwoch, 13. März 2002, 14:45–15:00, HS 32
Wetting properties and interfacial molecular ordering of long chain alkanes — •Paul Lazar, Hauke Schollmeyer, and Hans Riegler — Max-Planck-Institut für Kolloid und Grenzflächenforschung
Adjacent to the interface the melting temperature of long chain N-alkanes (e.g. C30H62) is higher than the bulk melting temperature Tb (No-dqsurface freezingNo-dq). Thus, above Tb, solid and liquid alkane coexists in thermodynamic equilibrium. This leads to peculiar wetting phenomena because the liquid alkane bulk wets its own solid only partially (liquid alkane droplets on a solid alkane layer). The melting of the solid monolayer coincides with a wetting transition from partial to complete wetting. The liquid alkane bulk can also be undercooled below Tb (although it is in contact with its own solid). Instead of the solidification of the entire alkane bulk, one observes on the substrate surface the growth of solid alkane multilayers underneath and besides the liquid alkane droplets (configuration like No-dqeggs, sunny side upNo-dq). This multilayer formation can create surface tension gradients which lead to the lateral movement of the liquid alkane droplets (Marangoni effect). This droplet movement is reversible and can be controlled by the substrate temperature through the growth and melting of the alkane multilayers.
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2.) C. Merkl, T. Pfohl, and H. Riegler, Phys. Rev. Lett. 79(2): 4625 (1997)