(363h) Fully Zwitterionic Copolymers: New Frontiers in Nonaqueous Gel Electrolytes

Copolymers synthesized from two or more monomers bearing distinct zwitterionic functional groups (i.e. polyzwitterions) represent a unique class of polyampholytes. As zwitterionic moieties abound in nature, this has likely led the majority of prior research efforts on synthetic polyzwitterions to focus on their behavior in aqueous environments. Our group, however, has recently been exploring their self-assembly within nonaqueous ionic liquids (room temperature molten salts).^1-4 Importantly, we have observed that fully zwitterionic copolymers can successfully form 3D networks within various ionic liquids to promote gelation via dipole-dipole and/or dipole-ion interactions. Such polymer-supported, ionic liquid-rich gel electrolytes (ionogels) have already demonstrated promise as safer, nonvolatile materials for future electrochemical energy storage devices, including lithium-ion batteries and supercapacitors. Fully zwitterionic, statistical copolymers that are synthesized in situ within different ionic liquids via UV-initiated free radical polymerization enable composition-dependent gel properties that can be tuned by varying the molar ratio between the two zwitterionic monomers (e.g. sulfobetaine and phosphorylcholine).¹ We have also recently begun exploring the effects of copolymer architecture, reporting the very first fully zwitterionic ABA triblock copolymers, which show spontaneous self-assembly behavior both in solution as well as in spin-coated thin films.² Interestingly, when lithium ions are present in nonaqueous, ion-dense systems featuring fully zwitterionic copolymers, the formation of either high stiffness/brittle or highly stretchable/self-healing gel composites is possible, depending on the immediate solvation environment surrounding the small cation.^3,4 This work illuminates some of the fascinating self-assembly behavior of polyzwitterions within ionic liquids, much of which we are still just beginning to uncover.

¹M.E. Taylor, M.J. Panzer, J. Phys. Chem. B 2018, 122, 8469-8476.

²M.E. Taylor, S.J. Lounder, A. Asatekin, M.J. Panzer, ACS Materials Lett. 2020, 2, 261-265.

³A.J. D’Angelo, M.J. Panzer, Chem. Mater. 2019, 31, 2913-2922.

⁴A.J. D’Angelo, M.J. Panzer, Adv. Energy Mater. 2018, 8, 1801646.