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 (M_w) ranging from 51k to 940k Da, infiltration is investigated in an NPG with a fixed pore radius (R_p = 34 nm) under moderate confinement (Γ = R_g/R_p) 0.18 to 0.78. The time for 80% infiltration (τ_80%) scales as M_w^1.43, 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 τ_80% for P2VP and PS, as well as molecular dynamics (MD) simulations. Simulations show that infiltration time scales as M_w^1.4 and that infiltration slows as the polymer–wall attraction increases. As M_w 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.