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The dielectric and conductometric properties of aqueous polyelectrolyte solutions present a very complex phenomenology, not yet completely understood, differing from the properties of both neutral macromolecular solutions and of simple electrolytes. Three relaxations are evident in dielectric spectroscopy of aqueous polyelectrolyte solutions. Near 17 GHz, water molecules relax and hence this highest frequency relaxation gives information on the state of water in the solution. At lower frequencies in the MHz range, free counterions respond to the applied field and polarize on the scale of the correlation length. This intermediate frequency relaxation thus provides information about the effective charge on the polyelectrolyte chains, and the fraction of condensed counterions. However, the presence of polar side chains adds a further polarization mechanism that also contributes in this intermediate frequency range. At still lower frequencies, the condensed counterions polarize in a non-uniform way along the polyelectrolyte chain backbone and dielectric spectroscopy in the kHz range may determine the effective friction coefficient of condensed counterions. In this review, we analyse in detail the dielectric and conductometric behaviour of aqueous polyelectrolyte solutions in the light of recent scaling theories for polyelectrolyte conformation and summarize the state-of-the-art in this field.

The authors have performed an extensive series of dynamic light scattering measurements of a three-component water-in-oil microemulsion system, consisting of AOT/water/decane, throughout the isotropic one-phase region at water to AOT molar ratio X=40.8, covering wide ranges of volume fraction phi and temperature T above and below the percolation threshold. The droplet density correlation function at long time has a nonexponential form for phi >0.4 and below the percolation threshold. When fitted to a stretched exponential function the apparent exponent beta , starting at about 0.7 at the lowest temperatures, increases continuously and approaches unity at the percolation temperature and above. The initial and the average decay rates of the correlation function, as a function of temperature, show an abrupt change of slope at the percolation threshold.

We present the dielectric relaxation spectra of non-spherical shelled particles (namely cylindrical and toroidal particles) with a layer of localized electrical charges at the interfaces, uniformly dispersed in a continuous aqueous phase. Our numerical simulations extend over a wide frequency range, covering both the relaxation region due to the presence of localized layers of charges at the interface (α-relaxation) and the one due to the mismatch of the permittivity and conductivity of the adjoining phases (β-relaxation or the Maxwell–Wagner effect). Although there is a general formulation for determining the electrical polarizability α(ω) of arbitrarily shaped particles, based on the knowledge of the internal electric field distribution, the presence of the localized charge distribution makes its use formally rather elaborate. Contrarily, in this paper we show that, in the dipolar approximation, the polarizability α(ω), assuming the same functional dependence for spherical, cylindrical and toroidal particles, can be calculated in a very simple way and that the dielectric (and conductometric) properties of particle suspensions, adopting a simple inductive procedure, can be treated under a unifying scenario. Moreover, the method holds both for homogeneous and heterogeneous layered particles. A detailed prediction of the dielectric relaxations for both α- and β-processes in heterogeneous systems composed of spherical, cylindrical and toroidal particles is made for a wide range of electrical phase parameter values.

Recently, the dielectric properties of haemoglobin's suspending medium inside human erythrocytes have been studied in the frequency range from 0.1 to 250 MHz (Jenin and Schwan Biophys. J., vol.30, p.235, 1980). It was found that in this frequency range, the erythrocyte water content exhibits rotational mobilities similar to those in pure liquid and the interior of erythrocytes has electrical properties consistent with those of a standard haemoglobin solution. In particular, dielectric and conductometric measurements have shown no evidence of an interaction between the cell membrane and the adjacent water. To verify these conclusions by direct observations, the authors present measurements on the dielectric properties of erythrocyte suspensions, carried out at a frequency of 10.0 GHz in the temperature interval from 5 to 45 degrees C. They also present a comparative analysis between the dielectric properties of homozygous beta -thalassemic red blood cells and normal cells.

The effect of a volume distribution of charges around the dispersed particles in an uni-univalent electrolyte solution on the dielectric properties of the colloidal system has been taken into account and a simplified theory has been developed. The results show that the characteristic parameters of the Maxwell-Wagner dielectric dispersion are affected by these volume polarisation effects; the correction terms, depending on some parameters of the system are also reported and their magnitude evaluated in particular cases.

We report low-frequency measurements of the electrical conductivity of charged colloids in an aqueous solution containing a simple electrolyte as aggregating agent. The measurements are performed as a function of time in a regime where the aggregation is diffusion limited. The results for the relative increase of conductivity can be described in terms of an asymptotic power law in time with an exponent 0.73???0.01. A possible connection of this exponent with the fractal dimension df of the clusters formed by aggregation is given.