Seclusion of molecular layers in a confined simple liquid

Abstract

We provide theoretical evidence by using molecular dynamics that a nanoconfined film of octamethylcyclotetrasiloxane divides into manifolds of secluded thermodynamic substates. We find equivalence between the splitting into substates and the formation of molecular layers. The seclusion of layers is validated in drainage experiments using an extended surface forces apparatus (eSFA). Furthermore, per-molecule evaluations of the configurational entropy provide evidence for an increased molecular packing upon confinement. The increasing trends in both layer seclusion and molecular packing with confinement explain the exponentially increasing surface forces measured in eSFA.