Slow dynamics and structural arrest in chemical and colloidal gels

Lucilla de Arcangelis

Department of Information Engineering, Second University of Naples, Via Roma 29, I-81031 Aversa (CE), Italy

In polymer gelation the transition from a viscous fluid into an elastic disordered solid is well understood in terms of a spanning cluster formation, which makes the system able to bear stresses. The dramatic changes in the viscoelastic properties, resulting in the divergence of the viscosity and the onset of an elastic modulus, can be well described in terms of percolation where the bonds between monomers are permanent. In colloidal systems at low temperature particles are linked due to attractive interactions but bonds are not permanent as in chemical gelation. We present the results of three-dimensional Monte Carlo simulations of a lattice model for gelling systems. We discuss the case of chemical gelation, where bonds are permanent, and characterize the critical dynamics with the formation of a percolating cluster. By introducing a finite bond lifetime, the dynamics displays relevant changes and eventually the onset of a glassy regime.