Transport in fluctuating supercooled and glassy nanoparticle matrices

Confined transport within slowly relaxing and structurally disordered matrices governs important processes in physical and biological systems, including polymer nanocomposites, membrane separations, and migration within crowded cells. Anomalous transport often arises in these settings from the competition between the multiscale relaxations of the disordered matrix and the dynamics of the confined particles. This competition depends on both the structure of the matrix and the nature of its relaxations. The connection between matrix relaxations and penetrant transport properties, however, remains incompletely understood despite the strong relevance for many physical transport processes. Here, I will describe experimental and computational studies probing how bulk confinement and matrix relaxations modulate the transport of tracer particles in supercooled or glassy nanoparticle matrices. These studies explore how fluctuations arising either from local rearrangements (due to cage-breaking) or long-wavelength modes (which become more pronounced as systems are increasingly confined towards two dimensions) can alter the particle dynamics and their ability to explore space.