Collective dynamics effect transient subdiffusion of inert tracers in gel networks

Based on extensive Brownian dynamics simulations we study the thermally driven motion of a tracer bead in a cross-linked, dynamic gel network in the limit when the tracer bead’s size is of the same size or even larger than the equilibrium mesh size of the gel. The analysis of long individual trajectories of the tracer bead demonstrates the existence of pronounced transient anomalous diffusion, accompanied by a drastic slow-down of the gel-bead relaxation dynamics. From the time averaged mean squared displacement and the van Hove cross-correlation function we elucidate the many-body origin of the non-Brownian tracer bead dynamics. Our results shed new light on the ongoing debate over the physical origin of sterical tracer interactions with structured environments.