Structure–Function Relationships in Membrane-Based Hydrocarbon Separations Using N-Aryl-Linked Spirocyclic Polymers

The separation of crude oil into its many components by distillation is an energy-intensive process. Membrane-based separations that avoid the use of heat can significantly reduce these energy requirements but are not yet able to obtain sufficiently high levels of molecular discrimination. While we have recently demonstrated initial success in the ability of membranes to fractionate crude oil, a better understanding of the relationship of polymer structure to membrane function will be necessary to design the library of membranes necessary to reduce the energy intensity of separation systems. In this work, we explored structural changes to a polymer, SBAD-1, that has shown exemplary membrane performance. The results suggest that, while aromatic interactions between solute and polymer impart favorable separation properties, polymer backbone rigidity has a much greater effect on membrane performance in organic solvent reverse osmosis separations, and an intermediate degree of rigidity is likely to be optimal.