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A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.

It's alive! A polymer gel has been developed that can generate a peristaltic motion without external stimuli. The motion is produced by dissipating the chemical energy of an oscillating reaction that occurs inside the gel. Although the gel is solely composed of a synthetic polymer, it shows independent motion as if it were alive. The motion of the gel can be harnessed to transport objects with millimeter dimensions (see picture).

A novel self‐oscillating gel actuator with gradient structure, which generates a pendulum motion by fixing one edge of the gel without external stimuli was achieved. The gel was synthesized by copolymerizing the ruthenium catalyst for the Belousov‐Zhabotinsky reaction with N‐isopropylacrylamide and 2‐acrylamido‐2‐methylpropane sulfonic acid. Furthermore, we clarified that the period and amplitude for the self‐oscillating behavior of the gel actuator are controllable by changing the composition, temperature, and size of the gel. The maximum amplitude of the novel gel actuator is about a 100 times larger than that of the conventional self‐oscillating gel system.magnified image

Here we report the biomimetic polymer that causes self-oscillation driven by the addition of biorelated organic acid. We constructed the built-in system where all of the substrates of the BZ reaction other than biorelated organic substrates were incorporated into the polymer chain. The quarternary copolymer, which includes both of the pH-control and oxidant-supplying sites in the poly(N-isopropylacrylamide-co-Ru(bpy)3) chain was synthesized. By using the polymer, we first succeeded in causing the self-oscillation of the polymer only in the coexistence of organic acid.

A novel self-oscillating polymer was prepared by copolymerizing the catalyst for the Belousov-Zhabotinsky reaction with N-isopropylacrylamide. Further, by introducing acrylamide-2-methylpropane sulfonic acid (AMPS) with a sulfonic acid group as a pH-control site into the polymer, self-oscillation under acid-free conditions was achieved. The period and amplitude for the self-oscillation is controllable by changing the composition of the polymer. On-off switching of self-oscillation is also possible by changing temperature or substrate concentrations. The AMPS plays an important role not only to control the pH but also to change the solubility of the polymer.

We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.