The effect of surface active agents on the microelectrophoretic properties of a polystyrene latex dispersion. Microelectrophoretic studies

• Published in: Journal of colloid and interface science 1976-01, Vol.56 (3), p.426-442
• Main Author: Kayes, John B
• Format: Article
• Language: English
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(76)90109-0

The effect of adding anionic (sodium alkyl sulphates), cationic (alkyltrimethylammonium bromides), and nonionic (polyoxyethylene glycol monoethers of n alkanols) surface active agents, and mixtures of these ionic and nonionic species, on the electrophoretic properties of a monodisperse polystyrene latex dispersion has been studied. The nonionic surfactants are probably adsorbed in a looped monolayer as shown by a plateau region in electrophoretic mobility versus concentration plots. With cationic surfactants adsorption is a two-stage process characterized by neutralization of negative charge followed by charge reversal. The free energy of adsorption is dependent on alkyl chain length, the adsorption process being controlled by the hydrophobic effect. Displacement of the reversal of charge concentration by nonionic surfactant depends on its concentration and the type of cationic surfactant. Adsorption of anionic surface active agents causes an increase in zeta potential. An estimate of the free energy of adsorption can be made from the slope of the zeta potential versus log concentration surfactant plot. Added nonionic surface active agents are found to complex with anionics, complexation being dependent on ethylene oxide chain length.