Physicochemical investigations on microemulsification of eucalyptol and water in presence of polyoxyethylene (4) lauryl ether (Brij-30) and ethanol

The microemulsification of eucalyptol/polyoxyethylene(4)lauryl ether (Brij-30)/ethanol/water has been investigated. The phase behaviours of the mixed system in pseudoternary and tetrahedral representations have been examined to understand the topological nature of the multicomponent mixtures. Phase volumes of the heterogeneous combinations have been estimated to understand the mixing efficacy of the combinations. Shear viscosities of different monophasic compositions have been measured at different shear rates and temperatures, and the activation parameters for the viscous flow have been evaluated. The dimensions of the nanodispersions of w/o and o1w types, their diffusion coefficients and the polydispersity have been determined by the DLS method. The energetics of solubilisation (dissolution) of water in oil + Brij-30 + ethanol as well as oil in water + Brij-30 + ethanol forming w/o and o/w microemulsions, respectively, have been calorimetrically determined. Considering the phase separation point to be the point of maximum solubility, the energetic parameters (enthalpy, free energy and entropy) of the microemulsification process have been estimated. (C) 2001 Published by Elsevier Science B.V.