Advances in the molecular design of ionenes for a diverse range of applications

Ionenes are polymers that have charges in their backbone rather than on pendant sites. They can be divided into two overarching categories whether the charge is cationic or anionic, and into two subcategories whether they are segmented or non-segmented polymers. Generally, segmented ionenes exhibit thermoplastic elastomer properties due to their low charge density and phase separation compared to non-segmented ionenes. Non-segmented ionenes have been widely used for the various applications ranging from membrane-based separations to biomedical materials; whereas, segmented ionenes have been mostly studied on a fundamental level. This review focuses on trends in the use of non-segmented ionenes in the above applications and more. Furthermore, it describes the properties of segmented ionenes, with attention to the relationships between the structure and function of the segmented ionenes. Together, this review offers insight into the design of ionenes for use in a diverse set of applications.