Spatial entrainment of patterns during the polymerization of acrylamide in the presence of the methylene blue–sulfide chemical oscillator

Turing-like patterns formed during the polymerization of acrylamide in the presence of sulfide, methylene blue and molecular oxygen are presented. We propose a chemical model of the polymerization of acrylamide in the presence of sulfide and oxygen. The model explains the formation of Turing patterns in this system. The experimental process of pattern formation becomes light sensitive if methylene blue is added. A space-periodic perturbation may thus be introduced into the system and spatial entrainment effects can be studied. The perturbation was realized by imposing an illumination pattern upon the reactive layer: after mixing the gel components and the MBO system in a Petri dish, a mask made of transparent film was placed between the light source and the dish. At different perturbation wavelengths we observed synchronization with the perturbation as well as irregular responses.