Infiltration of polymers into nanoparticle packings to produce highly loaded nanocomposites

Conventional methods of nanocomposite fabrication involve mixing and dispersing nanoparticles into a polymer matrix, making it challenging to produce composites with extremely high volume fractions (> 50 vol%) of nanoparticles. Recently our group has shown that such nanocomposites in the forms of films and membranes can be produced by capillary rise infiltration (CaRI) and solvent-driven infiltration of polymer (SIP). CaRI induces imbibition of polymer into the interstices of the nanoparticle packing via capillarity. In SIP, polymer infiltration is induced by exposing a bilayer of polymer and nanoparticle, which induces capillary condensation of the solvent in the interstitial voids of the nanoparticle packing and subsequent plasticization of polymer, leading to polymer infiltration into the solvent-filled interstices of the nanoparticle packing. While these methods provide powerful ways to produce highly loaded nanocomposites, they also provide a rich platform to study the behavior of polymers under extreme nanoconfinement. The chain dimension of the polymer, which depends on its molecular weight, can be comparable to or greater than the average pore size of the nanoparticle packing. In this talk, I will share our current understanding of the transport phenomena of polymers under such nanoconfinement using a combination of experimental and computational approaches. I will show that the dynamics of CaRI and SIP depends strongly on the confinement ratio as well as the molecular weight of the polymer. In particular, the effective viscosity of the polymer can decrease or increase depending on the extent of confinement and the molecular weight of the polymer. We also show that the structure and properties of the resulting nanocomposites also depend strongly on the processing parameters and the molecular weight of the polymer.