Suspensions of poly(vinylferrocene)-coated latex particles

Adsorption force of polyaniline-coated polystyrene latex particles

Visible polyaniline-latex particles 13 microm in diameter were used for obtaining a quantitative relationship between the adsorption force and the electroactivity at a platinum electrode. An optical cell equipped with wire electrodes was filled with the suspension in hydrochloric acid. When electrode potential was switched between the oxidized and the reduced domains, some adsorbed particles showed color change owing to the electroactivity. The numbers of electroactive and the inactive particles in the suspension were counted, including poly(N-vinylpyrrolidone) (PVP). The ratio of the numbers was proportional to the concentration of PVP, as it was in equilibrium. The adsorbed particles were desorbed mechanically by forced flow. The numbers of the desorbed particles did not decrease with an increase in the flow velocity until threshold values. The threshold value for the electroactive particle was 10 times larger than that for the inactive ones, corresponding to 10 times larger adsorption energy of the electroactive particles than of the inactive ones. The adsorption stress was evaluated from the removal of the electropolymerized polyaniline film from the electrode. Then the adsorption area of the particle was estimated.

Voltammetry of suspensions of hollow particles with ferrocene-immobilized polyallylamine shells

Redox-active hollow spheres were prepared through extracting a polystyrene core from the latex particle (PSPAAFc) composed of the core and the polyallylamine shell including ferrocenyl carboxylic amide. The suspension of the hollow spheres showed anodic and cathodic voltammetric peaks, which were nearly reversible and diffusion-controlled. The current was 3 times as large as the current for the suspension of the filled PSPAAFc. This value agreed with the theoretical one evaluated from the diameter (1.28 microm), the number of ferrocenyl moieties per particle, 1.2 x 108, by UV spectroscopy, and the diffusion coefficient obtained from the Stokes-Einstein equation. This fact indicates the reaction of the whole loaded charge, in contrast to the partial charge transfer of PSPAAFc. The dynamic flattening motion was observed to support the reaction of the whole charge.

Enhancement of electrochemical activity by small-sizing the vinylferrocene-immobilized polystyrene latex particles

Voltammetry of vinylferrocene (VFc)-immobilized polystyrene(PS)-based latex particles was carried out in aqueous suspensions by changing the size of latex particles in order to investigate the dependence of the electroactivity of the particles on their size. The anodic peak current was controlled by diffusion of the latex. The voltammetric peak currents increased with an increase in the diameter of PS latex particles for a given analytical concentration of the particles, exhibiting the dependence on 1.5 powers of the diameter of the particles. The increase can be explained in terms of combination of the uniform distribution of VFc in the particle, the partial charge transfer, and the Stokes-Einstein equation for diffusion coefficients. The oxidation of VFc occurs in the restricted domain (0.07 microm) from a contact point of the particle with the electrode. The overall reaction mechanism is diffusion of the particle to the electrode, partial oxidation to VFc+, release of VFc+ from the particle to the solution, and reduction of the released VFc+.