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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.66: Poster

Donnerstag, 29. März 2001, 15:45–18:15, Foyer S\ 3

Counterion evaporation — •Christian Fleck and Hans Hennig von Grünberg — Fachbereich Physik, Universität Konstanz, 78457 Konstanz

We study the adsorption behavior of a highly-charged rod-like polyelectrolyte approaching an oppositely charged planar wall in an unbounded electrolyte solution. The grand potential, the entropy and the total number of screening particles are calculated as a function of the rod-wall distance, using input parameters that are typical of a DNA-molecule and charged lipid-bilayers. It is found that counterions which are bound to the polyelectrolyte at infinite rod-wall distances, will be released, or ”evaporated”, as the DNA molecule moves closer to the charged wall. This effect can be regarded as the opposite of the ion-condensation process. The transition of ions from the system of screening ions into the reservoir of bulk ions can lead to an increase of enthalpy. This gain of enthalpy for the whole system manifest itself as an attractive contribution to the effective interaction between the wall and the polyelectrolyte.