Nanoconfinement Effects on Intermolecular Forces Observed via Dewetting.

Although wettability is a macroscopic manifestation of molecular-level forces, such as van der Waals (vdW) forces, the impact of nanoconfinement remains unexplored in predicting ultrathin film stability. In this work, we investigate how nanoconfinement influences intermolecular interactions using a polystyrene (PS)/poly(methyl methacrylate) (PMMA)/PS trilayer system, with PMMA thickness ranging from 15 to 95 nm. We find that the top PS layer's dewetting behavior is highly sensitive to underneath PMMA thickness, deviating from classical vdW-based predictions that assume bulk material properties. By incorporating nanoconfinement-induced changes in the PMMA refractive index, we modify the theoretical framework and successfully capture the observed behavior. This study provides direct evidence that nanoconfinement in soft matter significantly influences long-range intermolecular interactions, presenting a new opportunity to modulate film stability solely by adjusting underlying layer thickness while preserving the chemistry of the top functional film, ideal for performance-targeted interface design.