A New Method for Determination of the Adsorption Isotherm of SDS on Polystyrene Latex Particles Using Conductometric Titrations

Monodisperse polystyrene (PS) latex particles were prepared through a conventional batch emulsion polymerization procedure. After cleaning, the latex was subjected to a surfactant titration by sodium dodecyl sulfate (SDS) and the conductivity was monitored. Using the break point in the conductivity‐concentration curve, the adsorption area of the surfactant molecules at saturation, A_s, was determined as 46 Ų per SDS molecule. In order to determine the contribution of the different ionic species to the conductivity, a simple model based on experimental conductivity measurements was developed. The degrees of counterion binding to the micelles and to the surfactant anions adsorbed onto polymer particles were calculated as 0.770 and 0.849, respectively. The Langmuir adsorption isotherm was determined for the adsorption of SDS onto PS latex particles with Γ_∞ = 7.257 · 10^–10 mol/cm² and K = 1.208 · 10⁵ cm³/mol.