Metastable Dynamics of Colloidal Hard Spheres

Colloid hard spheres have been extensively used for the last two decades as a simple experimental system for investigating fundamental mechanisms of freezing and the glass transition, with relevance to phase transitions in atoms, small molecules and polymeric materials. Suspensions of colloidal hard spheres begin to crystallize at volume fractions above 0.494. Above 0.545 the entire sample will crystallize. Between these two volume fractions, the equilibrium state is a two-phase fluid-crystal co-existence. Samples above ~0.57 do not crystallize, but rather form a glass, which evolves into a disordered and out-of-equilibrium system, called colloidal glass. Such a system exhibits very slow dynamics and ageing behaviour making the experiments difficult. The aim of this research is to resolve fundamental issues in our understanding of freezing and glass transitions by systematically studying the dynamics of colloidal hard sphere suspensions in their metastable state as functions of volume fraction f and scattering wave vector q. We used several Dynamic Light Scattering techniques to characterize the dynamics of colloidal hard sphere suspensions. Improved data and analysis allow for the extraction of parameters which can be used to better understand the behaviour of metastable fluids, and may lead to a deeper understanding of crystallisation and glass transition. In this talk I will present some recent results of the dynamics of colloidal hard spheres in the full range of volume fraction, then focus on the glass region. Implications for understanding the ageing process will be discussed.