Recent Advances in Self‐Oscillating Polymer Material Systems

Abstract

In 1996, we first reported self-oscillating polymer gels exhibiting autonomous swelling-deswelling oscillations driven by the Belousov-Zhabotinsky reaction. In contrast to conventional stimuli-responsive gels, the self-oscillating gel can autonomously and periodically change its volume in a closed solution without any external stimuli. Since the first report, the novel concept of self-oscillating gels has been expanded into various polymer and gel systems. Herein, we summarize recent advances in self-oscillating polymers and gels.

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition

“…The self-oscillating gels were designed by utilizing the Belousov–Zhabotinsky (BZ) reaction, which is a well-known chemical oscillatory reaction that results in periodic redox changes and the emergence of spontaneous spatio-temporal patterns. Since this pioneering work, we have systematically studied these self-oscillating polymers and gels from nanoscale to bulk range sizes34. In doing so, the potential of these polymer systems for applications, for example, as biomimetic actuators, mass transport systems and functional fluids was explored.…”

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

“…[17,18] TheB Zr eaction proceeds with the slow oxidation of an organic substrate (for example malonic acid (MA)) by an oxidant (such as sodium bromate) in the presence of ametal catalyst (for example Ru(bpy) 3 )and protons.Importantly,the redox state of the metal catalyst changes periodically during the reaction. [19,20] Atypical design of the self-oscillating polymer is astatistical copolymer of N-isopropylacrylamide (NIPAAm, aw ellknown polymer having al ower critical solution temperature (LCST) in aqueous solution) and aR u(bpy) 3 metal catalyst that is modified with ap olymerizable vinyl group (P(NIPAAm-co-Ru(bpy) 3 ). [17,18] Our group has developed self-oscillating polymeric materials that convert energy from chemical oscillation of the BZ reaction into mechanical motion of the polymer network.…”

“…These spatiotemporal phenomena under nonequilibrium states are understood as aphysicochemical model of self-organization, analogous to many biological systems.In contrast to the conventional BZ reaction that requires strong acid, al ong-lasting and stable oscillation with ah igher frequency under milder condition can be successfully realized in hydrated PILs. As the hydrophilicity of the polymer changes with the redox state and the LCST is higher in the oxidized state,r edox changes of the Ru(bpy) 3 moiety during the BZ reaction induce cyclic changes of hydration/dehydration of the polymer chains.T hus,acorresponding autonomous swelling-deswelling self-oscillation of the gel starts spontaneously in the BZ reaction solution, without added catalysts or any external on-off switches.Since the initial report, [20] we have systematically developed selfoscillating polymer materials and systems including nanoactuators,polymersomes with self-beating motion, and afunctional fluid exhibiting amoeba-like locomotion. [19,20] Atypical design of the self-oscillating polymer is astatistical copolymer of N-isopropylacrylamide (NIPAAm, aw ellknown polymer having al ower critical solution temperature (LCST) in aqueous solution) and aR u(bpy) 3 metal catalyst that is modified with ap olymerizable vinyl group (P(NIPAAm-co-Ru(bpy) 3 ).…”

Design of a Tunable Self‐Oscillating Polymer with Ureido and Ru(bpy)3 Moieties

“…[1][2][3][4][5][6][7] Our research group has developed another class of smart materials known as "self-oscillating" polymers that autonomously undergo periodic soluble-insoluble or swelling-deswelling changes driven by an oscillating chemical reaction referred to as the Belousov-Zhabotinsky (BZ) reaction. [8,9] We have demonstrated the utility of self-oscillating materials as autonomous biomimetic materials,such as autonomous transport tubes, [10] artificial cells and amoeba composed of block copolymers, [11,12] and autonomous functional surfaces composed of polymer brushes. [13,14] Theb asic chemical structure of the self-oscillating polymer is ar andom copolymer composed of N-isopropylacrylamide (NIPAAm) and tris(2,2'-bipyridine) [Ru(bpy) 3 ]a s ac atalyst for the BZ reaction.…”