Chemomechanical Motion of a Self‐Oscillating Gel in a Protic Ionic Liquid

Abstract An autonomous swelling–deswelling oscillation of polymer gels in a hydrated protic ionic liquid (PIL) as a proton source for the Belousov–Zhabotinsky (BZ) reaction is presented. Methylammonium hydrogen sulfate ([maH + ][HSO 4 − ]) was employed as the PIL because it provides stable redox oscillation in the BZ reaction. Due to the significantly higher p K a for [maH + ][HSO 4 − ] than those for conventional proton sources for the BZ reaction, chemomechanical oscillation can be expected under weaker acidic conditions. The self‐oscillating polymer was designed as a ternary random copolymer of N ‐isopropylacrylamide, N ‐(3‐aminopropyl)methacrylamide, and the Ru(bpy) 3 moiety as a catalyst for the BZ reaction. The copolymer exhibited spontaneous soluble–insoluble oscillation in hydrated [maH + ][HSO 4 − ] containing NaBrO 3 and malonic acid. Macroscopic swelling–deswelling oscillation of the porous bulk gel prepared by covalently connecting microgel particles was also observed.