Chemical separations are essential to modern society. Without separations, our access to clean water, air, energy, medicine, food, and safe environment is critically restricted. Membrane-based separations draw significant attention due to their energy efficiency, small footprint, and ability to separate different molecular mixtures based on size, shape and interaction differences. Indeed, polymer membranes play central roles in gas, liquid and vapor separations, resource recovery, energy storage, barrier and packaging applications, and health-related devices. These technologies are vital for sustainability and decarbonization as we move to meet climate targets.

To advance these technologies, designing innovative polymer membranes with desirable transport properties and precisely controlled microstructures is required. In particular, charged polymer membranes, where anionic or cationic groups are covalently bonded to polymer backbone, draw significant attention due to their versatile and tunable transport properties in the above applications. Altering charged group composition combined with polymer architecture and topology leads to varied transport properties of small molecules (e.g., ions, water, gases) in polymer membranes. Here, research projects are presented for designing charged polymer membranes for improved molecule separations. The transport mechanism in the polymer membranes is studied from the fundamental perspectives of polymer-penetrant interactions and templating diffusion pathways for selective transport of small molecules.