Solvent-Driven Infiltration of Polymer (SIP) into Nanoparticle Packings

Despite their wide potential utility, the manufacture of polymer-nanoparticle (NP) composites with high filler fractions presents significant challenges because of difficulties associated with dispersing and mixing high volume fractions of NPs in polymer matrices. Polymer-infiltrated nanoparticle films (PINFs) circumvent these issues, allowing fabrication of functional composites with extremely high filler fractions (>50 vol %). In this work, we present a one-step, room-temperature method for porous PINF fabrication through solvent-driven infiltration of polymer (SIP) into NP packings from a bilayer film composed of a densely packed layer of NPs atop a polymer film. Upon exposure to solvent vapor, capillary condensation occurs in the NP packing, leading to plasticization of the polymer layer and subsequent infiltration of polymer into the NP layer. This process results in a porous PINF without the need for energy-intensive processes. We show that the extent of polymer infiltration depends on the quality of solvent and the duration of solvent annealing as well as the molecular weight of the polymer. SIP can also be induced using a slightly poor solvent, which offers a great advantage of inducing SIP via liquid solvent annealing, eliminating potential hazards associated with solvent vapor annealing. The SIP process circumvents challenges associated with dispersing high concentrations of nanoparticles in a polymer matrix to prepare a nanocomposite film with high filler fraction. Thus, SIP is a potentially scalable method that can be used for the manufacturing of porous PINFs of a wide range of compositions, structures, and functionalities for applications in structural and barrier coatings as well as electrodes for energy storage and conversion devices.