AMI seminar: Serge Ravaine

Room 170.048, Adolphe Merkle Institute, Marly

Thursday, April 8th, 2010  15:00 h

Synthetic routes towards "colloidal molecules"

Prof. Dr. Serge Ravaine

Organised fluids, materials and structures, CNRS Bordeaux, Bordeaux, France

One area of particular effort recently is the use of colloidal particles as precursors in engineering new structures; this has been called colloid engineering. To date, most studies of colloids have used spherical particles due to the fact that surface tension favors spherical shapes in overall length scales. But many current applications require “colloidal molecules”, i.e. particles with a well-defined non-spherical shape and localized surface functions. We have developed a synthetic route for fabricating such colloids through a process based on a seeded emulsion polymerization of styrene. By varying the size of silica seeds, the number of latex particles growing on their surface could be thus controlled and a large panel of morphologies was observed, including line segments, triangles, tetrahedra, etc. We have also demonstrated these morphologies result from the minimization of an energy term, which is the sum of an attraction towards the centre and two-body particle repulsions which can balance the attractive central force. In specific conditions, planar colloids and « patchy » particles can be obtained. Because our method yields large quantities of colloidal molecules in pure form, the fabrication of new colloidal crystal structures can be envisaged. For instance, making 3D photonic crystals with a full photonic band gap, a goal that has not yet been achieved, would be much easier if colloids could form crystals with a diamond lattice. Tetrahedral colloids might do just that.