Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 29: POSTER: Polymer physics
CPP 29.62: Poster
Dienstag, 8. März 2005, 16:30–18:30, Poster TU D
Counterion-Condensation Transition at Charged Polymers — •Ali Naji1,2 and Roland R. Netz1,2 — 1Physics Department, Technical University Munich, James Franck Strasse, D-85748 Garching, Germany — 2Physics Department, Ludwig Maximilian University, Theresienstrasse 37, D-80333 Munich, Germany
Charged polymeric systems are in many cases influenced by electro-statistic effects induced by neutralizing counterions present in the solution. A particular example is the so-called counterion-condensation process at charged extended polymers, which can trigger such striking phenomenon as aggregation of like-charged polymers in the DNA condensates and actin bundles. Counterion condensation emerges as a threshold process, i.e. counterions condense around the chains when the linear charge density of polymers exceeds a certain threshold; below that threshold, counterions diffuse away into the solution. Our chief goal is to examine the statistical properties of the counterion-condensation process near the threshold point for the model system of counterions at a charged cylinder (cylindrical cell model). It is shown that this threshold process is in fact characterized by a set of scaling relations for "order parameters" (as well as other thermodynamic quantities), which will be determined using a novel Monte-Carlo sampling method and also using the standard mean-field (Poisson-Boltzmann) theory. Our results for the scaling exponents indicate that the threshold counterion condensation is described by the mean-field universality class in both two and three spatial dimensions, and thus contrast previous speculations that it belongs to the Kosterlitz-Thouless phase transition class.