Adsorption of macromolecular surfactants on polystyrene latex particles and the rheology of the resulting dispersions

The effect of adsorption of macromolecular surfactants on the stability and rheological properties of latex dispersions has been investigated using adsorption isotherms and rheological measurements. Two latex particles with diameters of 427 and 867 nm were used and two macromolecular surfactants with poly(methyl methacrylate) backbone and poly(ethylene oxide) side chains were studied. It was found that the amount of adsorbed surfactant per unit area was approximately constant for both latex particles. The adsorbed amount increased with increase of temperature as a result of reduction of solvency of the medium for the chains. The steric interaction of the particles at saturation adsorption of macromolecular surfactants was investigated using rheological measurements, namely steady-state shear stress-shear rate and oscillation measurements. The adsorbed layer thickness of surfactants on the latex particle was determined as a function of volume fraction of the dispersions.