Effect of Gel Network on Pattern Formation in the Ferrocyanide–Iodate–Sulfite Reaction

Abstract

Stationary patterns have been researched experimentally since the discovery of the Turing pattern in the chlorite-iodide-malonic acid (CIMA) reaction and the self-replicating spot pattern in the ferrocyanide-iodate-sulfite (FIS) reaction. In this study, we reproduced the pattern formation in the FIS reaction by using poly(acrylamide) gels. Gels with different swelling ratios were prepared to use as a medium. The effect of the swelling ratio was compared with the effect of thickness. It was found that the swelling ratio greatly influenced pattern formation. Oscillating spot patterns appeared at high swelling ratios, and lamellar patterns appeared at a low swelling ratio. Self-replicating spot patterns appeared in between the two areas. The front velocities, which were observed in the initial stage of pattern formation, depended on the swelling ratio. Furthermore, this dependence obeys the free volume theory of diffusion. These results provide evidence that the change in front velocities is caused by a change in diffusion. Pattern formation can be controlled not only by thickness but also by swelling ratio, which may be useful for creating novel pattern templates.

Pattern Formation in Heterostructured Gel by the Ferrocyanide–Iodate–Sulfite Reaction

“…Furthermore, we showed the effects of a gel network density on pattern formation in the FIS reaction. The differences in the diffusivity were clearly observed as the shifts of the transition points and differences in the front velocities in a previous report …”

“…The differences in the diffusivity were clearly observed as the shifts of the transition points and differences in the front velocities in a previous report. 24 In our heterostructured gel, the diffusivity is low in Gel (20) due to its high network density. The low diffusivity shifts the transition from low pH to high pH to a higher flow rate.…”

“…A CSTR covered with a gel was constructed as shown in Figure . , The reactor consists of two reactors, A and B. The gel was set in the space between reactor B and its cover separated by 0.2 mm thick silicone rubber with a cellulose nitrate membrane (Whatman: 0.45 μm) and Anodisk (Whatman: 0.2 μm).…”

“…In addition, various functions can be chemically designed. We have created an autonomously oscillating gel by combining the Belousov–Zhabotinsky reaction with temperature-responsive hydrogels and functional polymers. − Moreover, we have tried to control pattern formation in the FIS reaction by controlling solute diffusion via the network density of polymer gel …”

“…19−23 Moreover, we have tried to control pattern formation in the FIS reaction by controlling solute diffusion via the network density of polymer gel. 24 In this study, we tried to form patterns by the FIS reaction in a heterostructured gel medium. A heterostructured gel with different network density domains was prepared.…”