Formation of trapped meta-stable liquid–vapour interfaces in polar liquids in presence of excess gas-like molecules: Anomalous heat capacities and emergence of microscopic bubbles

[Display omitted] •Lattice based Monte Carlo simulation for both canonical and grand-canonical systems have been used to confirm the formation of trapped-meta-stable interfaces in finite size systems with semi-infinite boundary condition.•We have obtained liquid structures and have evaluated properties as density profile, phase coexistence behavior, radial distribution function, adsorption isotherm, specific heat capacity and entropy. We have explored the underlying physics behind partial to complete wetting phenomena giving rise to different meso-scale structures.•Our results confirm that the irreversibility due to stacking of atoms in extremely narrow geometries and the associated inaccessibility of important microstates leads to the formation of trapped meta-stable states or in some cases quasi-equilibrium structures. The final structures are an outcome of the reconciliation between molecular interactions, interfacial energies and the extent of physical confinement.•The computational model for our case study fully explores the process of interface formation and successfully accounts definite reasons for the associated negative heat capacities for finite size systems, which has been riddling scientist for many decades. The negative heat capacities can be clearly associated with the instability of the liquid structures. Moderate and high surface affinities to liquid like molecules are found to create trapped-meta-stable states leading to the anomalous negative heat capacities as a direct consequence.•Last but not the least, the work also serves as a model to explain the mechanism of surface dewetting especially caused by meta-stable-phase separation in liquids. The presence of excess gas-like molecules is found to significantly influence the liquid–vapor equilibrium structures. We have elucidated the wetting behaviour of a polar-liquid in contact of an attractive planar surface. The formation of meta-stable liquid column-like structures, separated by vapour phase molecules, forming liquid–vapor interfaces, has been investigated in confined planar geometry. We have used lattice based Monte Carlo simulation for both canonical and grand-canonical systems. The presence of excess gas-like molecules has been reported to alter partial wetting conditions due to excess pressure in canonical ensemble. The system is driven towards formation of microscopic liquid–vapor interfaces, and the distinct liquid–vapor interface forming bridge-like structures disappear at hig