Finely Tuning the Lower Critical Solution Temperature of Ionogels by Regulating the Polarity of Polymer Networks and Ionic Liquids

Nonvolatile ionogels have recently emerged as promising soft electrolyte materials due to their high ionic conductivity and good durability. However, the compatibility between polymer networks and ionic liquids (ILs), which show significant influence on the physicochemical properties of the ionogels, has been rarely studied. Herein, we elucidate a lower critical solution temperature (LCST)-type phase behavior of ionogels composed of polyacrylates and hydrophobic 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ILs. We systematically study the structural effects of ILs and monomers on the LCST of ionogels. Our work illustrates that the LCST of ionogels is primarily determined by the polarity of polymer side chains and the alkyl chain on cations of ILs. The oriented solvation between polymers and ILs caused by hydrogen-bonding effects and van der Waals interactions may serve as the driving force for the LCST phase behavior in our system. Furthermore, by varying the mixing ratio of two structurally similar ILs in their blends, the LCST of ionogels can be tuned to exhibit a linear variation within a wide temperature range (from subzero to over 200 °C). Finally, thermoresponsive ionogels with desired patterns are prepared using photomasks. These nonvolatile ionogels with tunable LCST enriched the functionality of state-of-the-art ionogels, which provides insight into the design and fabrication of smart and flexible electronic/optical devices.