(3dg) Structure/Property Relationships in Polymer Membranes for Water Purification and Power Generation

Global demand for clean water and renewable energy sources is increasing.  These demands are inherently related because energy is required to purify water and, in most cases, purified water is required to produce energy.  Polymer membranes are widely used in desalination applications, such as reverse osmosis (RO), nanofiltration (NF), forward osmosis (FO), and electrodialysis (ED), and they could be critical for many renewable power generation technologies, such as pressure-retarded osmosis (PRO), reverse electrodialysis (RED), and fuel cells.  Improved membranes with tailored water and salt transport properties are required to extend and optimize these technologies.  Structure/property relationships must be used to provide the fundamental framework for optimizing polymer materials for applications that require tailored water and salt transport properties.

Water and salt permeability, sorption, and diffusivity structure/property relationships are presented for a series of dense, nonporous polymers that include crosslinked poly(ethylene glycol diacrylate) hydrogels, sulfonated polysulfone random copolymers, and sulfonated styrenic pentablock copolymers.  Salt transport through a polymer film depends, to a great extent, on whether or not the polymer is charged (e.g., sulfonated), and the effects of polymer charge on water transport and salt permeability, sorption, and diffusion are discussed.  Additionally, the effects of polymer structure modifications, such as crosslinking and varying block copolymer architectures, are discussed to further demonstrate how water and salt transport properties can be tuned.  Finally, water and salt transport data are modeled to further describe the permeability, sorption, and diffusion properties that govern water and salt transport.