Nanoscale dewetting and unpredictable dynamics of cyclic liquid in curved and rough nanochannels

Understanding of the behavior of liquids in nanochannels remains a challenging task and unsolved puzzle. Many different approaches/theories are developed to explain physical phenomena such as alteration of dynamics and shift of the glass transition temperature (T_g) reported for nanoconfined systems. Recent studies have linked these effects to the interfacial energy and wettability, typically measured on flat, polished surfaces. However, this approach overlooks a critical factor: under nanoconfinement, liquids interact with highly curved and rough pore surfaces, which can fundamentally alter their behavior. This study explores the thermal, dynamic, and interfacial properties of cyclic dimethylsila-17-crown-6(DMS17C6) confined in anodic aluminum oxide (AAO) mesopores with either constant (const-AAO) or modulated diameters (modul-AAO). We found a series of unexpected differences between both systems, i.e., different dynamics of confined liquid and T_g, reversible vs permanent confinement effects, and various time-dependent behavior. Notably, wettability change, inferred from the measurements of adhesion force within the pores by Atomic Force Microscopy, was found to be highly sensitive to the pore roughness, leading to unexpected behavior of cyclic liquid. These observations correlate with the permanent acceleration of structural relaxation dynamics, suggesting nanoscale dewetting despite apparent wetting at macroscopic scales. This discrepancy highlights the limitations of conventional contact angle measurements and underscores the necessity of nanoscale probes to accurately characterize interfacial interactions. The results also reveal the unique role of DMS17C6's cyclic molecular topology in the behavior of this molecule in nanospatial confinement. These findings provide new insights into nanoconfined liquid behavior, emphasizing the need to account for nanoscale pore roughness in theoretical models.