Electrodeposition of latex particles in the presence of surfactant: Investigation of deposit morphology

Abstract

The deposition of micrometric latex particles on a polarized nickel surface was investigated using a laminar flow cell equipped with a video assembly used to observe and record particle behavior near the electrode. The effects of the nature of the counterions and the concentrations of surfactants on the deposit structure were studied. Negative polystyrene latex particles were turned positive by adsorption of cetyltrimethylammonium in the form of different salts: bromide (CTAB), chloride (CTAC), and hydrogenosulfate (CTAHS). Image analysis was used to gain information on the mechanisms of particle deposition on the electrode. At CTAB concentration 5 × 10 −5 M, mostly single particles were deposited on the electrode and their adhesion was irreversible. The adsorption mechanism was shown to be dependent on the succession of electrophoretic migration and attractive particle–surface interactions. At a higher CTAB concentration (5 × 10 −4 M) a transient 3D aggregation was observed which was attributed to electroosmotic and electrohydrodynamic phenomena in the vicinity of the electrode. In the presence of CTAC, aggregates were formed on the electrode for both concentrations. In the case of CTAHS the deposition rate was very low in comparison with CTAB and CTAC. This result was explained by the lower zeta potential of the particles with respect to the other cases. The formation of the aggregates was reversible; furthermore, their morphologies were strongly dependent on the kind of counterion. The aggregates formed in CTAB solution were dense while more open structures were observed with CTAC.