Kinetic arrest and glass-glass transitions in short-ranged attractive colloids

摘要

In self-assembly processes, the importance of short-ranged interactions of controlled magnitude has been recognized for a long time. The well-known example is the crystallization of biological macromolecules in solution. However, a short-ranged attraction of a few κ_BT often leads to gelation or glassification in lieu of the much desired crystallization. Colloidal systems interacting via a short-ranged attractive potential (square-well) allow to mimic this scenario. In recent years, these systems have received considerable interest in terms of their dynamical properties. Mode coupling theory (MCT) and computer simulations have predicted two different types of glass transitions. In the conventional repulsive colloidal glass, the ergodicity is lost due to blocking of particle diffusion by the dense cages formed by their nearest neighbors whereas in the attractive glass, the particle motion is jammed even at low volume fraction (φ) by the short-ranged attraction or stickiness. These two glass lines meet at high φ, defining a reentrant transition of repulsive glass-fluidattractive glass as the attractive interaction is progressively increased. The attractive glass line extends beyond the reentrant region to a higher order singular point in MCT (A_3) delineating a glassglass transition. In experiments, similar dynamical arrest including the reentrant transition as that predicted by theory and simulation have been observed in a diverse class of short-ranged attractive colloidal systems. Attractive glass is a unifying term to describe the wide variety of dynamical arrest such as gelation, glassification, non-ergodicity transition, etc. induced by the stickiness.