Reentrant glass-fluid-glass transition in short-ranged interacting colloids

Theyencheri Narayanan (1) , Gabor Belina (1, 2) , Frédéric Pignon (2)

1 ESRF - European Synchrotron Radiation Facility
2 LR - Laboratoire de rhéologie

Recently, the colloidal systems interacting via short ranged attractive potential has received renewed attention in terms of their dynamical properties. Short ranged attractive colloids exhibit a rich variety of dynamical phenomena, e.g. gelling, glass transition, jamming, etc. The apparently different dynamical features of short-ranged attractive colloids can be unified in terms of a glass transition induced by attractive interaction which is referred to as an attractive colloidal glass transition. As a function of the strength of interactions and the colloid volume fraction, these systems exhibit two different glass transitions, fluid - repulsive glass at high volume fractions and the fluid - attractive glass at lower volume fractions with strong attraction. These two glass transitions merge at certain volume fraction defining a reentrant region of repulsive glass-fluid-attractive glass as a function of the strength of attraction over a narrow range of parameters. The distinguishing features of these two glasses lie in their rheological properties. Aim of this work is to relate the rheological/dynamical behaviour to the colloidal microstructure. Shear moduli G' and G" were measured as a function of the strength of attraction in the vicinity of the reentrant transition for different colloid volume fractions by a stress controlled rheometer using plate-plate geometry. The colloidal microstructure was deduced by ultra small-angle X-ray scattering (USAXS). The glass and the fluid states were identified from the frequency dependence of G' and G". With a small incremental change in volume fraction around 0.52, the system exhibits fluid-attractive glass, repulsive glass-fluid-attractive glass, and repulsive glass-attractive glass transitions. The rheological parameters showed orders of magnitude change across these transitions but static structure factor varied only little. This demonstrates the purely dynamical character of these glass transitions.

Domaines: Mécanique des fluides [physics.class-ph]; Matière Molle [cond-mat.soft]

Theyencheri Narayanan, Gabor Belina, Frédéric Pignon. Reentrant glass-fluid-glass transition in short-ranged interacting colloids. Second Annual European Rheology Conference 2005, Apr 2005, Grenoble, France. ⟨hal-00351935⟩