For distribution - thanks

[CM ICTP - Trieste]

Joint ICTP/Democritos

INFORMAL SEMINAR on Chemical Physics



Seminar Room - Main Building   (first floor)



Wednesday, 31 October -     4:00 p.m.



F. SCIORTINO  ( Universita' degli Studi di Roma 'La Sapienza' and 
CNR-INFN SOFT )



"Patchy colloidal particles: The role of the valence in the formation 
of gels"


Abstract

I will discuss thermodynamic and dynamic properties of simple models of 
particles interacting via a small number of localized  patches. I will 
show that  the resulting reduced number of bonded neighbors  has 
interesting consequences on the thermodynamic of the system. More 
specifically,
(i) the region of the phase diagram where liquid-gas coexistence is 
observed
is significantly reduced as compared to the isotropic interaction case.
(ii) the wider region of stability of the liquid phase favors the 
establishment of  a homogeneous disordered material at small packing 
fraction, which can be named accordingly "equilibrium gels"  or 
"network glass".
(iii) it becomes possible to generate liquid states (i.e.  states with 
temperature lower than the liquid-gas critical temperature) with a 
vanishing occupied packing fraction, a case can not be realized with 
spherically interacting particles;

Finally, I will show that for particles with a small number of patches 
it is possible to derive a fully predictive parameter-free theory of 
equilibrium self-assembly by combining the Wertheim theory for 
associating liquids with the Flory-Stockmayer approach for chemical 
gelation.