Self-oscillating gel composed of thermosensitive polymer exhibiting higher LCST

Abstract

We have developed self-oscillating polymers and gels as novel biomimetic materials by utilizing an oscillating reaction, known as the Belousov–Zhabotinsky (BZ) reaction. The self-oscillating polymer gel is composed of a poly(N-isopropylacrylamide) (PNIPAAm) network in which the catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the gel undergoes spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli. In order to induce self-oscillation while maintaining a larger amplitude at higher temperatures and around body temperature for potential applications to biomaterials, etc., here we prepared a self-oscillating gel composed of a thermosensitive N,N′-ethylmethylacrylamide (EMAAm) polymer exhibiting a higher LCST than that of the NIPAAm polymer. The self-oscillating behavior of the poly(EMAAm-co-Ru(bpy)3) gel was investigated by comparing against gels composed of a thermosensitive NIPAAm polymer with a lower LCST or non-thermosensitive N,N′-dimethylacrylamide (DMAAm) polymer. The design concept of self-oscillation at higher temperatures without a decrease in swelling–deswelling amplitude was demonstrated by utilizing a thermosensitive polymer exhibiting a higher LCST.