Control of Autonomous Swelling−Deswelling Behavior for a Polymer Gel

Abstract

We succeeded in the wide-range control of the period for the swelling-deswelling self-oscillation of a novel polymer gel by selection of the initial concentration of the Belouzov-Zhabotinsky (BZ) substrates and the temperature. The novel polymer gel was composed of a non-thermoresponsive and biocompatible poly(vinylpyrrolidone) (PVP) main chain covalently bonded to the ruthenium catalyst for the BZ reaction. In this study, we clarified the influence of the initial concentration of the BZ substrates and the temperature on the period and the self-oscillating behavior. By optimizing the initial concentration of the BZ substrates, we caused the swelling-deswelling self-oscillation in 0.5 Hz. The maximum frequency (0.5 Hz) of the novel gel was 20 times as large as that for the conventional-type self-oscillating gel. Moreover, we showed that the displacement of the self-oscillation for the gel has a tradeoff relationship against the period of the self-oscillation.

Autonomous Oscillation of Nonthermoresponsive Polymers and Gels Induced by the Belousov–Zhabotinsky Reaction

“…(Figure 11c). The period of the saturation point in Figure 11a is higher than that in Figure 11b,c, because of the higher mole fraction of the reduced Ru(bpy) 3 moiety in the gel [48]. In addition, at [MA] = 0.0625 M and [NaBrO 3 ] = 0.084 M (Figure 11c), the period can be changed by changing the initial concentration of the HNO 3 over a much wider range for the VP-based gel than for the poly(NIPAAm-co-Ru(bpy) 3 ) gel [59].…”

“…The equilibrium swelling ratios of the poly(VP-co-Ru(bpy) 3 ) gel in the reduced and oxidized states are shown in the Figure 10 [48]. No volume phase transitions are observed in either state because the volume of the VP-based polymer gel is not affected by the temperature.…”

“…In previous reports, Hara et al described various types of self-oscillating polymer systems with nonthermoresponsive main chains. Among them, we selected poly-vinylpyrrolidone (PVP) [48][49][50][51][52] and poly(2-propenamide) (polyacrylamide) (PAM) [53][54][55] for discussion here. As for the VP-based self-oscillating polymer chain, the influence of the concentrations of the three BZ substrates (sodium bromate, malonic acid, and nitric acid; not including metal catalyst) on the waveform and period of the self-oscillation was investigated.…”

Design of Autonomous Gel Actuators

“…To realize high-speed driving, we attempted to synthesize a novel self-oscillating polymer gel that drives without temperature limitation. In this study, we selected a non-thermo sensitive and biocompatible poly(vinylpyrrolidone) (PVP) as the polymer main chain of the novel self-oscillating gel (poly(VP-coRu(bpy) 3 gel)) [33]. As a result, we first succeeded in causing volume oscillation at a high temperature condition.…”

Self-Oscillating Structural Polymer Gels

“…The reaction includes a series of metalion-catalyzed oxidative reactions of organic substrates, such as malonic acid, by an acidified bromate solution. Recently, the BZ reaction has been used to induce mechanical oscillations in polymeric systems to mimic biological materials [3,4]. In particular, Yoshida and his co-workers have developed a self-oscillating cross-linked gel composed of stimuli-responsive poly-(N-isopropylacrylamide) (PNIPAM) polymer with grafted Ru(bipy) 3 moiety as the BZ catalyst [5,6].…”