Symmetries in Ionic Assemblies
M. Olvera de la Cruz
Department of Materials Science, Northwestern University USA
Mardi 26/06/2007, 11:00
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
Controlling features of self-organized architectures of viral size and shape has eluded scientists for decades. Using electrostatic forces we show the formation of ribbon-like helical (chiral) patterns on the surface of cylindrical fibers. Furthermore, through a straightforward approach we control the strength of the electrostatic interactions through the concentration of ions thereby having a mechanism to pattern the surface of virus-like fibers into chiral nanoaggregates with different pitch angles. In spheres, on the other hand, ionic assembly may lead to faceting. Shells of various viruses and other closed-packed spherical structures exhibit the highest symmetry, icosahedral symmetry. This is different from icosahedral shaped faceted structures found in large viruses, cationic-anionic vesicles, and other structures including fullerenes. The novel electrostatics driven faceting mechanism of ionic shells into icosahedral shapes breaks icosahedral symmetry due to different arrangements of the charged components amongst the facets. These shells appear in oppositely charged molecules co-assembled into membranes or adsorbed onto interfaces forming emulsions. \\ \\ 1. K.L. Kohlstedt, F. Solis, G. Vernizzi, and M. Olvera de la Cruz ``Spontaneous Chiriality via Long-Range Electrostatic Forces'' Phys. Rev Lett. (in press). \\ 2. G. Vernizzi and M. Olvera de la Cruz ``Faceting ionic shells into icosahedra via electrostatics'' (preprint).