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Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed.

Lecithin water-in-oil microemulsions have been shown to form long polymerlike micelles. Dielectric spectra of this system are characterized by two dispersions. The high frequency dispersion, related to the head-group rotation of the lecithin molecule, displays a different dependence on water addition in the same two regimes that show up differently in the dynamics measured with several other techniques. The low frequency dispersion is due to a polymeric Rouse/Zimm type mode, which above a certain concentration starts to decrease and shows the characteristics of percolation. In the high water regime the decrease of the relaxation time is accompanied by an increase in conductivity, whereas in the low water regime the conductivity decreases. These data are interpreted in terms of concentration induced percolation and water induced coalescence into a connected network.

Abstract. In this article, a system of amyloid fibrils, based on the protein β-lactoglobulin, is studied by transient electric birefringence. Single pulses of an electric field were applied to the solution, and the initial rise and subsequent decay of birefringence analysed. The decay takes place on a range of relaxation times, and therefore contains information about the length distribution of fibrils in the system. The information can be extracted using theories of the electric polarisability of polyelectrolyte rods, since the fibrils are an example of these. Despite the long-standing complications of such theories, useful quantitative information about the system can still be obtained. Using the Fixman model of polyelectrolyte polarisability, we obtain a measurement of the short end of the length distribution which shows the fibril concentration as a function of length rising linearly from 0.02-2µm. The short end of the length distribution was unobtainable in our previous study using rheo-optics (Rogers S. S. et al., Macromolecules 38, 2948Macromolecules 38, (2005, Iss. 8), but reasonable agreement between the two techniques shows they are complementary.