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MECHMOL Résumé de rapport

Project ID: IST-2001-35504
Financé au titre de: FP5-IST
Pays: United Kingdom

Determine effects of shuttling on properties

One of the crucial points to be tested was that the surface covered with light-switchable rotaxanes with the fluoroalkane region exposed (E-1) onto a SAM of 11-MUA on Au(111)/mica resisted UV illumination without degradation. For this purpose we exposed the surface to UV light for different periods of time and looked for signs of degradation by monitoring the oxidation of sulphur. Oxidation of sulphur gives rise to the appearance of an additional component in the S2p photoemission signal.

We could show that no oxidized sulphur was present neither on the freshly prepared sample, nor after 5 minutes of UV irradiation. After 10 minutes of UV irradiation the slight change in background around 168.5eV (oxidized sulphur) hinted at a commencement of sulphur, however only after 15 minutes a small component characteristic of oxidized sulphur could be identified with confidence. This meant that all experiments concerning property changes of the surface in response to UV light and consequent movement of a macroscopic object had to be performed within this time span.

In order to understand the interactions leading to macroscopic motions through the exploitation of rotaxane-based molecular machines the Bologna group used a phenomenological approach to obtain the rate of movement of the drop, focussing on the simulation of the interface between the rotaxanes and the drop. Experiments showed that the thermodynamics of interaction is subtler than expected. Indeed, the experimental contact angles, that according to Young law reflect the thermodynamics of the three-phase system, do not provide a simple explanation for the drop motion.


David LEIGH, (Professor)
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