Leaching-enabled capillary rise infiltration (LeCaRI) and lateral diffusion of poly(dimethylsiloxane) in nanoparticle packings

Capillarity-driven infiltration of polymers into the interstitial voids of nanoparticle packings provides a unique route to prepare highly filled nanocomposites. Additionally, the confinement of large polymer chains in nanopores of the packing alters the dynamics of polymers significantly from their bulk behavior. In this work, we induce infiltration of low glass transition polymers like polydimethylsiloxane (PDMS) from a gel network into the pores of silica nanoparticle packings by leaching-enabled capillary rise infiltration (LeCaRI). The amount of infiltrated polymer is governed by the interplay between two opposing factors: capillary pressure and capillary condensation of water. By using PDMS stamps with patterns, polymer infiltration can be limited to regions within the packing, creating patterned composites. Locally infiltrated polymer spreads laterally via surface diffusion. By tracking the spreading front via ellipsometry, mobility of chains under nanoconfinement can be inferred. We observe that high humidity leads to faster spreading of the polymers within the packings. Results on PDMS spreading behavior including rouse-like scaling of the diffusion coefficient with the molecular weight of the polymer will be discussed.