Nanoparticle dynamics in fully synthetic biomimetic analogues

Adding end-functionalized polymers to an emulsion produces hierarchical structures that percolate the material, significantly augmenting the material’s elasticity and introducing a finite yield stress. As a result, we find that this class of materials successfully replicate the structure, mechanics, and dynamics of soft, cellularized tissues. Here, we explore how nanoparticles transport through these polymer-linked emulsions with the goal of understanding transport in complex, biological systems. We vary the nanoparticle size, polymer concentration, and polymer molecular weight and evaluate how these properties affect transport properties, including long-time diffusivity, short-time localizations, and non-Gaussian distributions of displacements. Small particles exhibit faster-than-expected diffusion whereas large particles couple to the material viscoelasticity. Furthermore, nanoparticles readily explore space for samples prepared with a high molecular weight linker but are preferentially located in low permeability zones for emulsions containing a low molecular weight linker. We attribute these differences to the bridging probability of the polymers. Our findings elucidate how nanoparticle transport depends on structure, dynamics, and mechanics in dense suspensions and biological environments.