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CPP: Chemische Physik und Polymerphysik

CPP 15: Poster: Dünne Filme, Monolagen und Oberfl
ächen

CPP 15.8: Poster

Mittwoch, 13. März 2002, 16:30–18:00, B

Measurements of the Apparent Line Tension of Hexaethylene Glycol on Silanized Silicon Substrates — •Mika Kohonen, Frieder Mugele, Thomas Becker, Renate Nikopoulos, and Stephan Herminghaus — Angewandte Physik, Universitaet Ulm

We report measurements of the drop-size dependence of the contact angle of hexaethylene glycol droplets on silanized silicon substrates. By using a combination of standard contact angle measurements, microinterferometry and Tapping Mode atomic force microscopy we have been able to measure contact angles for droplets of macroscopic (1E-3 m), microscopic (1E-5 m) and submicroscopic (1E-7 m) dimensions. The value of the line tension obtained from such measurements varies over several orders of magnitude (1E-6 to 1E-10 J/m), depending on the range over which the contact angle dependence on drop size is examined. Our results confirm previous reports of the importance of surface heterogeneity in line tension measurements. We also describe how the large variability in both the magnitude and sign of reported values of line tension can be rationalised in terms of contact angle hysteresis.