Mechanically strong ionogels formed by immobilizing ionic liquid in polyzwitterion networks

Abstract

Recently, ionogels have obtained widespread attention as excellent functional materials due to their advantageous properties, such as nonvolatility, nonflammability, and good electrochemical properties. Herein, a novel two-component ionogel system exhibiting superior mechanical strength and flexibility, satisfactory self-healing property, as well as comparable electrochemical property is constructed through in situ photopolymerization. This kind of ionogels is free of any crosslinker and comprised of a polymerized imidazolium-type zwitterionic salt as polymer backbone and an ionic liquid 1-butyl-3-methylimidazolium chloride (bromide) as solvent. The zwitterionic groups interact strongly with each other and the ions of ionic liquid solvent, resulting in the formation of the physical crosslinking within the polymer chains and the ion-dipole interaction between the zwitterionic group in the polymer backbone and ionic liquid solvent which endow the ionogel with superior mechanical strength without any crosslinker. The compression strength and tensile strength can reach 58MPa and 2.3MPa, respectively. The mechanical performance of these polyzwitterion ionogels is even comparable to chemically crosslinked high strength ionogels reported. These tough ionogels also show good self-healing properties at their glass transition temperature and have 80% recovery of their original strength. Moreover, these ionogels exhibit comparable ionic conductivities and can be well-maintained even after successive bending or folding.