Role of Interfacial Rigidity on Electrical Conductivity and Electrolyte Exchange in the Infinite Droplet Clusters of Oil Continuous Microemulsions

The temperature-dependent electrical conductivity behaviour of concentrated microemulsion system of water/aerosol OT/isooctane with close packed droplets (wo = 20 and droplet volume fraction φ = 0.52) has been studied. The rigidity of the droplet interface has been modulated by adding n-propanol and cholesterol which decrease or increase the interfacial rigidity respectively of the microemulsion droplets by being dissolved into droplet interface. At a particular temperature, the charge propagation in the percolation range is much faster in the system containing propanol while i t is reduced considerably in the microemulsion containing cholesterol. The kinetics of the complexation reaction between chromium (III) and EDTA in such concentrated microemulsion have also been studied in the presence of propanol and cholesterol in order to find out the role of interfacial rigidity on the reaction rates. It has been demonstrated that in the concentrated microemulsions where the droplets remain in clusters, the reaction rate is considerably modulated with the change of interfacial rigidity of the droplets. We have concluded that the droplet interface acts as an effective activation barrier for the mass transportation of reactants among droplets in clusters and thus modulate the kinetics of reaction.