Interactions and kinetic arrest in an adhesive hard-sphere colloidal system

The evolution of microstructure and dynamics of a colloidal suspension transforming from hard-sphere to sticky hard-sphere system is investigated by small-angle x-ray scattering techniques. The colloidal system comprised of sterically stabilized silica particles suspended in a marginal solvent. The repulsive to attractive transition was realized by varying the temperature. While the particle form factor showed few changes, the structure factor of interparticle interactions exhibited liquidlike features in the attractive phase. The measured structure factors up to a gelation transition can be adequately described by the square-well model of short-ranged attractive fluids. The particle dynamics showed a continuous change from single to stretched exponential decay as the system transformed from repulsive to attractive behavior. A complete jamming of the particle dynamics was observed when the depth of attractive well attained several k(B)T. Although, static and dynamic behavior are reversible with respect to temperature, considerable hysteresis was noticed. The observed behavior is consistent with the existence of a gelation/attractive glass transition induced by the strong short-ranged attractive interaction in the colloidal gas-liquid coexistence region. (C) 2003 American Institute of Physics.