Colloidal gels and glasses inside a computer

Gelation has been observed experimentally for colloidal systems with short range attraction [1], and a recent theoretical work [2] rationalizes it within Mode Coupling Theory (MCT), therefore, as a glass transition. In this talk, I will present results on gelation from molecular dynamics simulations. At moderate and high densities, the gel transition is observed at decreasing interaction strength for increasing colloidal packing fraction. The position of this line relative to the crystallization or liquid-gas de-mixing will be discussed. Gelation is studied according to the predictions from MCT, and compared with the glass transition occurring at high density and low interaction strength. Bond formation has been identified as the driving mechanism leading to the gel transition, while steric hindrance is responsible for the glass transition. At high density and interaction strength, where the gel and glass transition lines merge, singular points may appear. This possibility will be discussed according to the simulation findings.

[1] W.C.K. Poon et al., Faraday Discuss. vol. 112, 143 (1999).

[2] K. Dawson et al., Phys. Rev. E vol. 63 011401 (2001).