Interest in the electrical properties of the interface between soft (or polymer-grafted)
nanoparticles and solutions is considerable. Of particular significance is the case of
polyelectrolyte-coated particles, mainly taking into account that the layer-by-layer procedure allows
the control of the thickness and permeability of the layer, and the overall charge of the coated particle.
Like in simpler systems, electrokinetic determinations in AC fields (including dielectric dispersion in
the 1 kHz–1 MHz frequency range and dynamic electrophoresis by electroacoustic methods in the
1–18 MHz range) provide a large amount of information about the physics of the interface. Different
models have dealt with the electrokinetics of particles coated by a single polymer layer, but studies
regarding multi-layered particles are far scarcer. This is even more significant in the case of so-called
salt-free systems; ideally, the only charges existing in this case consist of the charge in the layer(s) and
the core particle itself, and their corresponding countercharges, with no other ions added. The aims
of this paper are as follows: (i) the elaboration of a model for the evaluation of the electrokinetics of
multi-grafted polymer particles in the presence of alternating electric fields, in dispersion media where
no salts are added; (ii) to carry out an experimental evaluation of the frequency dependence of the
dynamic (or AC) electrophoretic mobility and the dielectric permittivity of suspensions of polystyrene
latex spherical particles coated with successive layers of cationic, anionic, and neutral polymers;
and (iii) finally, to perform a comparison between predictions and experimental results, so that it
can be demonstrated that the electrokinetic analysis is a useful tool for the in situ characterization of
multilayered particles.
