Thermal vitrification in suspensions of soft colloids: molecular dynamics simulations and comparison with experiments.

Dense suspensions of multiarm star polymers are known to develop liquidlike microstructure, which has been attributed to the similarities between high functionality stars and colloidal particles interacting via soft, long ranged potentials. Recent experimental studies reported a counterintuitive solidification of suspensions with f=128 , upon increase of the temperature in marginal solvents. We present our results from molecular dynamics simulations of dense suspensions of multiarm star polymers. Star polymers are modeled as "soft spheres" interacting via a theoretically developed potential of mean field. Our results show a transition towards a "glassy" state at a temperature very close to the one reported experimentally. The features of the transition are consistent with those of ideal glass transitions, as described by ideal mode coupling theory. Furthermore, our findings illustrate the road to vitrification for these soft-colloidal suspensions. Higher temperatures result in arm expansion that causes jamming and more than compensates for faster short time, temperature induced kinetics.