Prof. Achille Giacometti: Unconventional Phases in Helical Particles and Janus fluids
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Povzetek:
Unconventional Phases in Helical Particles and Janus fluids
Prof. Achille Giacometti, Department of molecular sciences and nanosystems, Universita' Ca' Foscari, Venezia, Italia
This talk has two parts. In the first part I will discuss the self-assembly properties of a fluid of helical particles modelled as chains of fused hard spheres arranged in a helicoidal fashion and interacting only sterically. I will show how a rich polymorphism is found, with strong departures from the spherocylinder phase diagram. Remarkable is the presence of a special chiral nematic phase with screw-like order, where helices are well aligned along the director and their C2 symmetry axes spiral around this direction with periodicity equal to the particle pitch. Screw-like ordering was observed in colloidal helical flagella. We have fully characterized this phase and show that it is a general feature in the phase diagram of helical particles. In the second part of the talk, I will discuss another uncoventional phase diagram occurring during a self-assembly process of Janus spherical colloids. The phase diagram includes a colloidal-poor (gas) colloidal-rich (liquid) phase separation, which is progressively suppressed by the insurgence of micelles. Finally, I will discuss recent developments obtained when extending the Janus paradigm to an anisotropic particle, that is a Janus “dumbbell”.
