How mechanical loading modulates non-ideal cosolute partitioning in hydrated polymeric membranes

This work examines the impact of mechanical forces on molecule (cosolute) transport through polymeric membranes in 1:1 salt solutions, considering the molecular information of the cosolutes. Our study highlights how strain-dependent cosolute partitioning between the membrane and the bulk solution is influenced by the interplay of size exclusion and specific binding interactions, with dielectric repulsion playing a dominant role in modulating multivalent cosolute partitioning. To gain a deeper understanding, we develop an analytical expression considering the mechanical stress and cosolute-membrane interaction, including the cosolute's chemical, electrical, and physical molecular information. We show that only elastic and osmotic contributions govern the stress–strain relationship of the membrane, regardless of its charge status. This approach provides a molecular-level representation of the chemical potential of cosolutes and their transport behavior under mechanical stress. The results establish a coupled theoretical framework for linking transport properties and mechanical deformation of polymeric membranes.