Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 2: Colloids and Nanoparticles
CPP 2.5: Vortrag
Montag, 27. März 2006, 11:15–11:30, ZEU 160
Mechanical properties of catanionic hollow faceted polyhedrons — •Nicolas Delorme1, Monique Dubois2, Thomas Zemb3, and Andreas Fery1 — 1Max Planck Institute for Colloid and Interface Research, Potsdam, Germany — 2SCM, CEA Saclay, Gif-sur-Yvette, France — 3LCF, CNRS/CEA URA 331, Gif-sur-Yvette, France
Mixtures of cationic and anionic surfactants dispersed in water show a rich polymorphism depending on the mixing ratio. For an excess of the anionic component, hollow facetted polyhedrons are formed which have been subject to detailed structural studies in the past.While our aim in this study is to understand the impact of electrostatic interactions on the mechanics of the catanionics, our results are also relevant for studies on viruses or facetted vesicles which are mechanically analogous. In this purpose, Atomic Force Microscopy (AFM) is used to measure elastic properties and other surface interaction forces. After the immobilization of the polyhedrons onto a flat surface using polylelectrolytes of tailored charge density, combining force measurements and imaging allowed demonstrating the strong dependence between the stiffness and the shape of the facetted polyhedrons. We have demonstrated that compared to a supported lipid bilayer in the gel-state, the catanionic membrane is very rigid, showing an effective bending modulus of up to 450 kT. In order to understand the origin of the rigidity of the catanionic membrane, the evolution of the mechanical properties were investigated as function of pH and salt concentration, which are know to change the electrostatic contribution to the bending stiffness.