Nonlinear Response of a Batch BZ Oscillator to the Addition of the Anionic Surfactant Sodium Dodecyl Sulfate

摘要

The response of the Belousov-Zhabotinsy (BZ) system to the addition of increasing amounts of the anionicudsurfactant sodium dodecyl sulfate (SDS) was monitored at 25.0 °C in stirred batch conditions. The presenceudof SDS in the reaction mixture influences the oscillatory parameters, i.e., induction period and oscillationudperiod, to an extent that depends on the surfactant concentration. The experimental results have shown thatudthe induction period increases slightly on increasing surfactant concentration and, then, a further increase inudthe [SDS] leads to an enhancement while the oscillation period increases monotonously on increasing SDSudconcentration. It has been proposed that the response of the oscillatory BZ system to the addition of SDS isuddue to the peculiar capability of the organized surfactant assemblies to affect the reactivity by selectivelyudsequestering some key reacting species. Indeed, explanations of the experimental results have been given onudthe basis of the role played by the micellar shape, which in turn dictates the hydrophobic nature. The suggestedudperturbation effects have been supported by performing viscosity measurements on the aqueous SDS solutionsudand by the spectrophotometric estimation of the binding constant of the bromine species to the micellarudaggregates. This study has indirectly corroborated the existence of two kind of micelles and unambiguouslyudrevealed that the bromine species show a different affinity toward the spherical and rod-like micelles.