On the nature of patterns arising during polymerization of acrylamide in the presence of the methylene blue sulfide-oxygen oscillating reaction

Transient Turing-like spatial patterns were recently reported by Munster et al. when the components of the methylene blue oscillator are mixed with acrylamide and a polymerization initiator to form a polyacrylamide gel. We have qualitatively reproduced these results, but we demonstrate that, although the observed patterns have the appearance of Turing structures, they actually result from Rayleigh-Benard convection in a mixture of acrylamide, N,N'-methylene-bisacrylamide, triethanolamide, sulfide ions and ammonium peroxodisulfate during the polymerization and gelation process. Neither methylene blue nor sulfite is required for patterns to develop. (C) 1998 Published by Elsevier Science B.V. All rights reserved.