Capillary Filling Dynamics of Entangled Polymers Under Moderate Confinement

Polymer infiltrated nanoporous gold can be prepared via capillary rise infiltration of polymers into a bicontinuous, nanoporous gold scaffold. The infiltration time based on the bulk dynamics of entangled polymer is expected to scale with the polymer molecular weight, τ_infiltration ∝ N^3.4, but numerous deviations from this scaling have been observed experimentally in different confining geometries. The nanoporous gold structure differs from previous studies due to both a moderate level of confinement and a bicontinuous pore geometry with zero mean curvature, unlike the concave cylindrical pores of AAO or the convex pores of nanoparticle packings. Here we present a computational study using molecular dynamics to understand the kinetics of entangled polymers undergoing capillary rise infiltration into nanoporous gold, finding a change in infiltration time scaling to τ_infiltration ∝ N^1.4 for weakly interacting entangled polymers. The smaller than expected exponent is attributed to a reduction in chain entanglement density during infiltration and a decrease in the fraction of chains adsorbed with increasing polymer molecular weight. These results align well with experiments of polystyrene infiltration into nanoporous gold. In addition, we explore the impact of polymer-gold interaction strength on infiltration kinetics, comparing these results to experiments infiltrating poly-2-vinylpyridine (P2VP), a polymer with strong attraction to gold.