Dresden 2006 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 17: Thin Films and Surfaces II

CPP 17.6: Vortrag

Mittwoch, 29. März 2006, 17:00–17:15, ZEU Lich

Experimental determination of the coverage-height dependence of self-assembled monolayers during film formation — •Ahmed Abd el Monem¹, Jana Wehrmeister², Mark Helm², and Michael Himmelhaus¹ — ¹Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg — ²Institut für Pharmazie und molekulare Biotechnologie, Universität Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg

So far, the adsorption kinetics of Self Assembled Monolayers (SAM) of alkanethiols on the coinage metals has been extensively studied. A lot of theoretical and experimental work has been done to evaluate the adsorption rate and layer thickness. However, measurements of the adsorption kinetics have been found to depend strongly on the method applied according to the physical transducer mechanism used to trace surface adsorption, such as the change in the dielectric properties of the interface or the alteration of surface state density. In this work, we present a novel approach, which combines linear and nonlinear optical techniques, i.e. spectral ellipsometry and optical second harmonic generation, to acquire such different information during the adsorption process of alkanethiolates on gold independently. Accordingly, by observing the adsorption of different alkanethiols (C4, C12, C18) in-situ the differences between the two methods could be clarified. Preliminary experiments carried out on the adsorption of alkanethiol-terminated polyethylene glycol demonstrate the potential of the method for the determination of the coverage-height dependence of surface-grafted polymer brushes, which is particularly important for direct comparison with theoretical predictions.