Dr. Igor Kulic "Non-Equilibrium Self Assembly by Coherent Dispersion Forces: Colloidal Membranes and Doughs"
ICS Strasbourg, France
What |
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When |
Jan 30, 2013 from 02:15 PM to 03:00 PM |
Where | Hörsaal Makromolekulare Chemie, Stefan-Meier-Str. 31, Freiburg |
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When polarisable objects are excited by a spatially randomly fluctuating medium and in turn interact, we speak of "Van der Waals – London" type dispersion forces. But what happens if the excitation is non-equilibrium and spatially coherent?
I will show that such a "coherent dispersion interaction" (CDI) has remarkable and distinctive physical features making it a practical, potentially important tool for colloidal self assembly of complex hierarchical materials.
Owing to these features, distinguishing it from its "incoherent sister" - the usual dispersion interaction- the CDI gives rise to complex hierarchically self assembled materials ("dipolar dough's") displaying local cohesion on small scales but an average repulsion on larger scales, inflating the material with a net positive pressure.
I will discuss a recent example, cleverly implemented with superparamagnetic colloids in triaxial magnetic fields by Martin et al. and illustrate the main steps in the hierarchical formation process of coherent colloid self assemblies, from elementary colloidal units, over the formation of chains, transition to membranes, to large scale foamy structure of the material set by the inter- membrane interactions.