Ambient stability and surface adhesion of 2D polyaramid nanofilms

Two-dimensional polyaramids (2DPAs) represent an emerging class of solution-synthesized, molecularly thin polymer sheets that combine the exceptional in-plane mechanical strength and barrier performance of conventional 2D materials with the synthetic versatility of organic polymers. Despite increasing interest in 2D polymers as gas barriers and membrane materials, the long-term stability of nanometer-scale suspended films remains largely unexplored. Here, we report the first longitudinal study of 2D polyaramid (2DPA-1) nanofilm bulges monitored continuously for over 1000 days. Using a microwell bulge test platform integrated with atomic force microscopy and optical interferometry, we show that 2DPA-1 forms highly stable, gas-retaining membranes whose upward deflection persists for years under ambient environmental fluctuations. Using a single-point mechanical model with thermodynamic analysis, we show that initial bulge pressurization proceeds through transient rim seal opening, while the intact seal remains robust during thermal cycling up to 120 °C without measurable gas loss. Together, these results establish a comprehensive mechanistic framework for long-term stability, permeability assessment, and interfacial failure modes in nanofilm bulge systems. This framework enables reliable interpretation of bulge test data and provides design principles for next-generation 2D polymer membranes intended for ultrahigh-barrier, filtration, and separation technologies.