Particle dynamics and vibrational properties of disordered colloidal packings with varying interparticle attraction strength*

We experimentally study dynamical and vibrational properties of disordered colloidal packings as a function of the strength of the interparticle attraction. ~Specifically, we probe the structural and dynamical changes in disordered colloidal glasses as the interparticle interaction between constituent particles evolves from nearly hard-sphere repulsive to attractive. ~This increase of the interparticle attraction is achieved through use of temperature-tunable surfactant micelle depletants. The depletion-driven entropic attraction between particles in suspension grows with increasing temperature. ~Increasing temperature changes particle interactions in a dense colloidal packing from repulsive (weakly attractive) to strongly attractive, and accompanying variations in structure and dynamics is investigated. ~Preliminary experiments on these disordered systems show a continuous change in particle dynamics as attraction strength increases. ~Interestingly, vibrational properties show a more sudden change reflected in the behavior of the vibrational density of states.