Oberseminar WS 2010 Guskova

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Simulation of Nanostructure Formation in Rigid-Chain Polyelectrolyte Solutions

Dr. Olga Guskova

Max Planck Institute of Colloids and Interfaces, Dept. Theory & Bio-Systems

Using a coarse-grained model, we performed molecular dynamics simulations of the electrostatically driven self-assembly of strongly charged polyelectrolytes and diblock copolymers (as well as multivalent counterions) composed of oppositely charged and neutral blocks. Stoichiometric micelle-like complexes formed in a dilute solution represent cylindrical brushes whose conformation is determined by the linear charge density on the polyelectrolyte and by temperature. The core?shell morphology of the cylindrical brushes is proven. The core of these anisotropic micelles consists of an insoluble complex coacervate formed by the ionic chains and a shell made up of the neutral solvophilic blocks. As the concentration of macromolecules increases, the orientational ordering of ionic micelles takes place. The complexation can induce effective steric stiffening of the polyelectrolyte chains.

Organization of Nanoparticles at the polymer brush-solvent interface

The organization of nanosized particles (NPs) in a polymer brush by DPD simulations was investigated. The brush is composed of flexible chains grafted by one end to a solid substrate. The polymer-insoluble NPs are treated as rather rigid aggregates of almost spherical form. Varying either the strength of interaction between polymer and NP beads or the concentration of NPs (i.e., the load by NPs) we observe particle cluster formation in the distal brush region. For low load, in agreement with theoretical predictions we demonstrate that the nanodroplet formed is vertically oriented and exhibits cylinder shape. With increasing concentration the aggregate at the rim of the brush becomes a flattened sphere. For high load, when the droplet-droplet interaction is significant, the cluster becomes highly anisotropic and the horizontally oriented nanodroplet adopts a cylinder (or baguette-like) shape.