Dielectric spectroscopy and conductivity of polyelectrolyte solutions

Abstract

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.

Interaction between like-charged polyelectrolyte-colloid complexes in electrolyte solutions: A Monte Carlo simulation study in the Debye–Hückel approximation

“…When a patch attraction is present but the complexes are not neutral, the competition between the residual repulsive interaction and the shorter ranged attraction determines a potential barrier, whose strength depends on the balancing between these two components. The presence of such barrier justifies [30] the aggregation behavior observed in several colloid-polyelectrolyte systems regulated by the amount of added polyelectrolyte chains [2,19,25,31,[42][43][44][45]58]. By adding a 'steric' contribution to the inter-particle potential, due to the overlapping of PE-layers, we recover the complete effective interaction between the decorated macroions.…”

“…We studied the effective interaction and the induced charge asymmetry of PE-colloid complexes within the Debye-Hückel approximation for the case where the monomer size is small compared with that of the adsorbing macroion and the surface charge density of bare colloids is characteristic of the extensively investigated spherical DOTAP liposomes [2,19,25,[42][43][44][45]58]. The interaction between non-neutral PE-decorated particles is purely repulsive for large screening length κR c ≪ 1 and it is well-described by a Debye-Hückel potential.…”

Electro-Optical Properties Characterization of Fish Type III Antifreeze Protein

“…The spectra show the relaxation of a macromolecular dipole. The experimental data of the real part of the permittivity e′(w; [15]. The best nonlinear fit parameters of the experimental data are: Δe=3.23±0.15; t=9.88 10 -8 ±1.04 10 -8 s; and e ∞ =84.5±0.1.…”

Label‐Free Impedance Biosensors: Opportunities and Challenges

“…This research area, termed dielectric spectroscopy [137], has received limited attention in the biosensing community [138][139][140] but tends to be applied to measuring bulk solutions at high frequencies (≫ 1 MHz, C surf negligible) and is thus quite distinct experimentally from conventional surface-sensitive impedance biosensors (≪ 1 MHz, C surf important). Some biomolecule dielectric relaxation effects may be detectable at frequencies in the kHz range [138,141]. However, these effects are usually neither surface-sensitive nor specific, so dielectric spectroscopy seems better suited to studying the behavior of biomolecules (e.g., [142]) than distinguishing between similar biomolecules.…”