Imparting Solvent Resistance to Polymers through Confinement in Nanoparticle Packings

One drawback of polymer-based products is their poor solvent resistance, as polymers tend to swell, deform and dissolve catastrophically when exposed to good solvents. In this work, we show that infiltrating polymers in the interstices of dense packings of nanoparticles can enhance their solvent resistance. We are inspired by previous research showing that a tightly bound layer of polymer can form on the solid surface and remain intact after exposure to good solvents. We investigate whether such seemingly irreversible polymer-surface adsorption affects the solvent resistance of polystyrene (PS) and poly(2-vinyl pyridine) (P2VP) confined within the interstitial pores of a SiO₂ nanoparticle (NP) packing. We vary the solvent quality, confinement ratio, and polymer-NP interactions to probe the regime of solvent resistance in these polymer-infiltrated nanoparticle films (PINFs). Our results indicate that PINFs with the smallest pore size have the best solvation resistance. PS-PINFs are less effective at resisting polar solvents, while P2VP-PINFs provide greater protection. Weakening the attractive polymer-NP interactions by alkyl silanization of the NP surface greatly reduces the solvation resistance. We hypothesize that when pore size is adequately smaller than the adsorbed layer thickness, the solvent cannot remove polymer chains from the composite. These results present a new technique to provide solvent resistance to polymeric materials for enhanced performance and novel applications.