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CPP: Chemische Physik und Polymerphysik

CPP 24: Polymer films II

CPP 24.4: Vortrag

Dienstag, 8. März 2005, 16:00–16:15, TU C130

NONEQUILIBRIUM CONFORMATIONS OF SINGLE ADSORBED POLYMER CHAINS — •Christof Ecker and Jürgen P. Rabe — Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin

Using Scanning Force Microscopy (SFM) single molecules adsorbed onto a flat surface can be imaged often with a resolution high enough to track the chain contours. This opens the possibility of polymer experiments on a single molecule base. In an earlier study it was found that conformations depend critically on the chain mobility on the surface [1]. A high mobility allows relaxation to the thermal equilibrium where chains can be described e.g. by the worm-like chain model. A low mobility on the other hand leads to a trapping of chains so that the conformations formed upon adsorption are preserved.

In my talk I will discuss the kinetics of chain adsorption onto low mobility surfaces and how the kinetics are related to the formed conformations. I will present results of MD simulations and also of SFM experiments. In the latter, two kinds of polymer systems were investigated: dendronized polymers [2] and double stranded DNA. The conformational characteristics observed are (1) sinusoidal undulations and (2) spirals. Both can be explained in the picture of a zipping process [3] as confirmed by the simualtions.

[1] Rivetti et al., J. Mol. Biol. 264, 919 (1996). [2] L. Shu et al., Macromolecules 33, 4321 (2000). [3] A. L. Ponomarev et al., Macromolecules 33, 2662 (2000).