Comparative analysis of complex liquids based on a multi-experimental approach.
A parallel analysis is here presented between the results gathered by the author by means of three different experimental approaches--Dielectric analysis, Thermally Stimulated Depolarization (TSD) and Differential Scanning Calorimetry (DSC)--on some multi-component complex liquids consisting of association structures of self-assembling amphiphiles as, water-in-oil microemulsions. The highly dispersed nature of these systems was evidenced with the dielectric study: a Maxwell-Wagner relaxation was found to characterize this type of systems. The structural evolution of the system, against water addition, was well described by the orientational processes induced in the liquid samples by a nearly static electric field as in the TSD method. The investigation by DSC, besides offering a basic picture of the system's thermodynamics, allowed the measure of the specific heat, at constant pressure, at the higher order percolative phase transition. The comparison between the results obtained on samples processed with identical thermal cycles, once under the action of an impressed electric field as in TSD, and, once in the absence of any impressed electric field as in DSC, did help distinguish three main concentration intervals within which structurally different systems form namely, isotropic microemulsions and two liquid crystalline structures of lyotropic type.
A cell for measuring the complex permittivity of lossy liquids at very high radio frequencies
A dielectric cell for investigating high permittivity liquids has been designed for use with a radio frequency admittance bridge. The cell has negligible self-inductance below 100 MHz and thus requires no corrections in its use. Details are given for modifying the bridge terminals when temperature control of the system is required.
Light Scattering Study of a Perfluoropolyether Ternary System
Abstract Ternary systems containing perfluoropolyether (PFPE) oil, PFPE surfactant, and water have been investigated using viscosity and static and dynamic light scattering. The existence of surfactant aggregates has been shown, and the dependence of their size and interaction on W/S ratio, oil molecular weight, and ionic strength has been investigated. Aggregate size increases with either water content or oil molecular weight, as typically found with hydrogenated microemulsions. Interactions among droplets become more and more attractive as W/S molar ratio is decreased or oil molecular weight is increased. Light scattering results have been discussed in comparison with conductivity and NMR; a correlation among high conductivity, water in continuous network, and aggregate attraction clearly emerges.