Influence of Belousov–Zhabotinsky Substrate Concentrations on Autonomous Oscillation of Polymer Chains with Fe(bpy)₃Catalyst

Abstract

We studied the effect of initial substrate concentrations in the Belousov-Zhabotinsky (BZ) reaction on the optical transmittance self-oscillation behavior of a polymer chain consisting of N-isopropylacrylamide (NIPAAm) and a Fe catalyst ([Fe(bpy)3]). The driving force of this transmittance self-oscillation was the solubility difference between the reduced and oxidized states of the [Fe(bpy)3] moiety in the polymer chain. The amplitude of the soluble-insoluble self-oscillation of poly(NIPAAm-co-[Fe(bpy)3]) was significantly smaller than that of poly(NIPAAm-co-[Ru(bpy)3]). Theoretical simulation results attributed this behavior to the small difference in the solvent qualities, C*, of the reduced and oxidized states. Furthermore, we clarified that poly(NIPAAm-co-[Fe(bpy)3]) required a narrower concentration range of HNO3 to exhibit self-oscillation than poly(NIPAAm-co-[Ru(bpy)3]), since transmittance self-oscillation occurred only for [HNO3] = 0.3 M. The period of self-oscillation of poly(NIPAAm-co-[Fe(bpy)3]) in solution was controlled mainly by NaBrO3 concentration and was hardly influenced by the initial concentration of malonic acid.

Preparation and characterization of poly(NIPAAm-co-AMPS-co-Fe(phen)3) self-oscillating copolymers

“…Some of them have been recently exploited for the design of SOPs. Hara et al [14,15] demonstrated that Ru(bpy) 3 catalyst could be substituted by Fe(bpy) 3 . Although the utilization of iron greatly lowers the cost for preparing the BZ reaction catalyst, the soluble-insoluble self-oscillating amplitude is smaller than that of Ru(bpy) 3 -based copolymer.…”

Effect of strong acid on the self-oscillating behavior for the polymer chain with the Fe(bpy)

“…To apply the self-oscillating polymer system to devices such as an autonomous pump system, the cost of the Ru(bpy) 3 moiety was regarded a problem because Ru is a rare metal. To reduce the cost of the metal catalyst moiety in the self-oscillating polymer system, Hara et al first synthesized a self-oscillating polymer chain with an Fe catalyst moiety (Fe(bpy) 3 ) for the BZ reaction [15,16]. In this study, the optical self-oscillating behaviors of the polymer chain with Fe(bpy) 3 were measured at constant concentrations of the three BZ substrates (malonic acid (MA; 0.1 M), sodium bromate (NaBrO 3 ; 0.2 M), and sulfuric acid (H 2 SO 4 ; 0.2 M)) and at constant several temperatures (T = 11, 12, 13, 15, 17, and 19°C).…”

“…In this study, the optical self-oscillating behaviors of the polymer chain with Fe(bpy) 3 were measured at constant concentrations of the three BZ substrates (malonic acid (MA; 0.1 M), sodium bromate (NaBrO 3 ; 0.2 M), and sulfuric acid (H 2 SO 4 ; 0.2 M)) and at constant several temperatures (T = 11, 12, 13, 15, 17, and 19°C). In previous studies [15,16], nitric acid was used as the strong acidic agent for the BZ reaction. In this study, we selected sulfuric acid as the strong acidic agent to confirm the influence of the oxidation power on the self-oscillating behavior of the polymer solution with Fe(bpy) 3 .…”

Self-oscillating soluble-insoluble changes of polymer chain induced by the BZ reaction with Fe(phen)3 catalyst

“…Therefore, it is necessary to construct a self-oscillating polymer system with a cheap metal catalyst moiety in order to expand its application. Recently, Hara developed a novel self-oscillating polymer by covalently bonding the Fe(bpy) 3 moiety to the polymer chain, which acted as the metal catalyst for the BZ reaction [27,28]. However, the amplitude of the soluble-insoluble self-oscillation of poly(NIPAAm-co-[-Fe(bpy) 3 ]) was significantly smaller than that of the corresponding Ru-based self-oscillating polymer system.…”