Turing Patterns and Waves in Closed Two-Layer Gel Reactors

Reaction–diffusion waves and stationary Turing patterns are observed in closed two-layer gel reactors, where the two compartments are initially filled with complementary sets of reactants of the chlorine dioxide–iodine–malonic acid–poly­(vinyl alcohol) reaction. The asymmetrical loading generates concentration gradients and the patterns form at the interface between the two parts. These easy-to-perform experiments allow us to study a wide range of dynamical phenomena without requiring a specific reactor design or the use of sophisticated equipment. To get complementary information on pattern formation in parallel and perpendicular to the direction of the concentration gradients, two geometrically different configurations of compartments are presented. We demonstrate that three variants of the initial distribution of the chemicals can be equally applied, and this flexibility provides a way to introduce additional reagents to perturb the dynamics of the systems. A noticeable increase in the wavelength of Turing patterns and in the period of waves has been induced by adding bromide ions. The interaction of Turing and Hopf modes has been observed as a result of not only the variation of the initial poly­(vinyl alcohol) concentration but that of the gradients as well