Chemomechanical oscillations in polymer gels: Effect of the size of samples

The appearance of chemomechanical oscillations in polymer gels during the Belousov-Zhabotinskii reaction is studied. The effect of the size of composite gels based on polyacrylamide and silica, as well as the gels of acrylamide-sodium acrylate copolymer, on the mode of the reaction and the period of oscillations is examined. It is established that there is a limiting gel diameter below which the chemical oscillations of the oxidation state of a catalyst do not result in the appearance of chemical waves: Redox transformations occur uniformly within the sample. The gel-size threshold value below which the mechanical oscillations of the polymer network are not observed is determined. On the basis of the comparison of phase difference between mechanical and chemical oscillations for samples of various sizes and data on the swelling degree of gel in equilibrium states in which the catalyst is in either the oxidized or the reduced state, a conclusion is made about the mechanism of volume oscillations of the polymer network.