Zeta potential study of a polystyrene latex with variable surface charge: influence on the electroviscous coefficient

Abstract

Electrophoretic mobilities of a carboxyl polystyrene latex have been measured against electrolyte (NaCl) concentration for different pH values. The aim of this study is to know how the changes in the surface charge density affect the electrokinetic behaviour of this latex and, particularly, the presence and position of the maximum in the mobility versus electrolyte concentration curves. Mobilities become greater with increasing surface charge and the maximum mobility becomes greater and is reached at higher electrolyte concentration. This behaviour is discussed by analysing the classical explanations (hairy layer, coion adsorption, surface conductivity) proposed. Zeta potentials have also been calculated using different mobility—zeta potential conversion theories and the results have been compared. These mobility-zeta potential conversion theories have also been tested with an experimental study that is different from the usual electrokinetic techniques: the primary electroviscous effect.