Molecular ordering and domain morphology of molecularly thin triacontane films at /air interfaces

Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Max-Planck-Campus Am Mühlenberg 1, D-14476 Golm/Potsdam, Germany

Received: 17 January 2000
Accepted: 23 October 2000

Abstract

The molecular ordering and the domain morphology of molecularly thin triacontane films at /air interfaces has been investigated at room temperature by scanning force microscopy, X-ray diffraction, and X-ray reflexion. Our results suggest that the room temperature structure is influenced by the surface freezing behaviour of triacontane, i.e. its solidification adjacent to the interface already some degrees () above the bulk melting temperature (). Depending on the amount of alkane available either a closed monolayer topped by separated chunks of bulk (solidified droplets) or, in the case of only submonolayer alkane coverage fractal, seaweed-shaped domains are observed. In both cases, adjacent to the interface the molecules are oriented upright and packed in a rectangularly centered unit cell with a lateral correlation of much more than 200 molecules. A fractal dimension of indicates that the domains are formed by diffusion-limited aggregation.