Gel-forming patchy colloids

Sciortino, F.^1
1 Dipartimento di Fisica, Università di Roma, Italy

I will discuss thermodynamic and dynamic properties of simple models of particles with patchy interactions. I will show that possibility of controlling the number of bonded nearest neighbors has interesting consequences on the thermodynamic of the system: 

(i) It reduces the region of the phase diagram where liquid-gas coexistence is observed

(ii) it offers the possibility of generating liquid states (i.e. states with temperature lower than the liquid-gas critical temperature) with a vanishing occupied packing fraction, a case cannot be realized with spherically interacting particles;

(iii) it opens up the region of stability of the liquid phase, favoring the establishment of homogeneous disordered materials at small packing fraction, which can be named accordingly stable equilibrium gels or network glasses.

I will show also how the process of self-assembly of the network can be described theoretically in a rather precise and I will discuss the connections between physical and chemical gels.
Recent literature related to this presentation includes:

[1] E. Bianchi, J. Largo, P. Tartaglia, E. Zaccarelli, F. Sciortino; Phase diagram of patchy colloids: towards empty liquids, Phys. Rev. Lett. 97, 168301, 2006

[2] Emanuela Bianchi, Piero Tartaglia, Emilia La Nave and Francesco Sciortino; Fully Solvable Equilibrium Self-Assembly Process: Fine-Tuning the Clusters Size and the Connectivity in Patchy Particle Systems, J. Phys. Chem. B 111, 11765 (2007).

[3] F. Sciortino, E. Bianchi, J. Douglas and P. Tartaglia; Self-assembly of patchy particles into polymer chains: A parameter-free comparison between Wertheim theory and Monte Carlo simulation, J. Chem. Phys.126, 194903, 2007

4] S. Corezzi, C. De Michele, E. Zaccarelli, P. Tartaglia and F. Sciortino; Connecting Irreversible to Reversible Aggregation: Time and Temperature, J. Phys. Chem. B (Letter) January 13 (2009) and Softmatter in press.