The separation efficiency of a membrane material is primarily governed by its structural and chemical attributes. Currently, most membranes are designed empirically, which limits the speed of their development and possibly their performance metrics. An improved understanding of the fundamental behaviors of complex mixtures incorporated within membrane materials is likely to lead to more rapid development of efficient membranes for separations. As a result, this project aims to correlate how membrane nanopores influence the phase separation of miscible solvent mixtures and how phase separation impacts solute dynamics. Phase separation of ethanol-water mixtures, in which phase separation is induced by the addition of large amounts of specific salts, are being evaluated so that the phase separation behavior within model cylindrical nanopores can be determined using optical spectroscopic and light scattering techniques. The mechanism of phase separation on solute permeability and dynamics within the nanopores are being elucidated using single-molecule optical spectroscopic and microscopic techniques as well as X-ray scattering methods. Knowledge gained from this research has the potential to inform solvent parameters that influence the transport and permeability of molecules under nanoconfined conditions.