Abstract
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.
Highlights
The investigation of the properties of nanoparticles is nowadays loaded with interest from the academic point of view (they can be considered in the crossing of fields of chemistry, materials science(their engineering and use as building blocks) or physics), interest in them has grown exponentially when more fields of application have been disclosed [1]
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 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) 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
It is shown that it is possible to modify the nanostructure of the polymer solution interface in the case of polystyrene particles, by coating them with different combinations of positive (PDADMAC), negative (PSS), or neutral (PEO) layers, using the layer-by-layer technique
Summary
The investigation of the properties of nanoparticles is nowadays loaded with interest from the academic point of view (they can be considered in the crossing of fields of chemistry (their synthesis), materials science(their engineering and use as building blocks) or physics (the explanation of their behaviour)), interest in them has grown exponentially when more fields of application have been disclosed [1] The generation of such applications has taken decades of research in the processes of particle synthesis and preparation [2], because, most often, they require to be further modified (or functionalized) to fit the desired application. Known, one of the procedures to make them stealthy is coating them with a suitable polymer one of the procedures to make them stealthy is coating them with a suitable polymer (poly(ethylenglycol)
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