Colloidal gels—low-density disordered solid-like states

The analogies between colloidal glasses and gels have stimulated an increased effort in recent years to unify the description of the transitions to these disordered solid-like states within a single conceptual framework. Mode coupling theory, which successfully describes the hard sphere colloidal glass transition, has been extended to describe the effect of weak attractions at large volume fractions. By comparison, diffusion limited cluster aggregation models successfully describe the behavior for the other limit, irreversibly aggregated, fractal gels formed at low volume fractions and very large interaction potentials. A theoretical picture, which unifies these two limits, is still the subject of research. In this review, we summarize some of the results obtained to date, aiming to give an overview of our current understanding.