Polymer–Wall Interactions Slow Infiltration Dynamics in Bicontinuous, Nanoporous Structures

Polymer infiltration is studied in a bicontinuous nanoporous gold (NPG) scaffold. For poly(2-vinylpyridine) (P2VP) with molecular weights (Mw) ranging from 51k to 940k Da, infiltration is investigated in an NPG with a fixed pore radius (Rp = 34 nm) under moderate confinement (Γ = Rg/Rp) 0.18 to 0.78. The time for 80% infiltration (τ80%) scales as Mw1.43, similar to PS, but weaker than the bulk behavior. Infiltration of P2VP is slower than PS due to stronger P2VP–wall interactions resulting in a physisorbed P2VP layer. This interpretation is supported by the similar scaling of τ80% for P2VP and PS, as well as molecular dynamics (MD) simulations. Simulations show that infiltration time scales as Mw1.4 and that infiltration slows as the polymer–wall attraction increases. As Mw increases, the effective viscosity transitions from greater than to less than the bulk viscosity due to pore narrowing and a reduction in entanglement density. These studies provide new insight into polymer behavior under confinement and a new route for preparing nanocomposites at high filler loadings.