The effects of the anionic surfactant sodium dodecyl sulfate (SDS) on the spatio-temporal and temporal dynamics of the ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction have been studied over a wide surfactant concentration range. For the first time, investigations were performed also for unstirred systems. The presence of SDS in the reaction mixture influences the oscillatory parameters to an extent that significantly depends on the surfactant concentration. The trend of the wave speed V upon the increasing amount of SDS was found to have a maximum at [SDS] ) 0.075 mol dm -3 (V ) 0.071 mm s -1 ), after which the speed decreased to 0.043 mm s -1 at [SDS] ) 0.5 mol dm -3 , which is below the value found in the absence of the surfactant (V ) 0.055 mm s -1 ). The response of the oscillatory BZ system to the addition of SDS has been ascribed to two different causes: (a) the peculiar capability of the organized surfactant assemblies to affect the reactivity by selectively sequestering some key reacting species and (b) the modifications induced by SDS on the physical properties of the medium. These hypotheses have been corroborated by performing spectrophotometric investigations on the stirred BZ system. Complementary viscosity measurements gave useful hints for the clarification of the surfactant role.

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This study is initiated by a recent discovery, according to which a water soluble polymer, poly(ethylene glycol) (PEG), affects the dynamics of the Belousov-Zhabotinsky (BZ) reaction in a characteristic way. As various polymers and polymer-based hydrogels are often applied in nonlinear chemical experiments, it is an interesting question whether the effect of a polymer can be attributed exclusively to its reactive endgroups (here primary alcoholic groups) or if the macromolecular nature of the perturbant might be also important. In this paper, as a first step, the results of batch experiments are presented applying only small molecules, namely ethylene glycol (the monomer of PEG) and methanol (a more simple primary alcohol), as perturbants of the BZ reaction. The reaction was followed by monitoring the rate of the carbon dioxide evolution. The experimental results are compared with model calculations, applying the latest model of the BZ reaction, the Marburg-Budapest-Missoula (MBM) mechanism extended with the perturbing reactions. The rate of the perturbing reactions (reaction of the acidic bromate with the alcohol producing the autocatalytic intermediate bromous acid) was determined in separate spectrophotometric experiments. Experiments and model calculations show a good qualitative agreement (alcoholic perturbations increase the induction period and the frequency of the oscillations and decrease the amplitude), but disagreements were found on a quantitative level. Because the mechanism of the alcoholic perturbation, especially in the case of methanol, is mostly clarified, it is the MBM mechanism which should be modified somewhat in the future. As the reaction dynamics responds to the alcoholic perturbations rather sensitively, simulating these perturbation experiments can help to test new mechanistic proposals for the BZ reaction.

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