Small-angle neutron scattering study of particle coalescence and SDS desorption during film formation from carboxylated acrylic latices

Four monodisperse core-shell latices were synthesized for small-angle neutron scattering (SANS) studies, differing by the acrylic acid content in the particle shell (I or 4 wt%) and the T-g of the acrylic core (around -40 or 10 degreesC). In a first part, the coalescence kinetics of the surfactant-free latices were studied. It was shown that coalescence was hindered by an increase in the acrylic acid content of the shell, pH of the latex, and T-g of the core. These results could be interpreted in terms of chain mobility in the shell and in the core. Upon coalescence, the hydrophilic phase was segregated in spherical, polydisperse domains with an average diameter of 110 nm. In a second part, labeled SDS was used to follow desorption of the surfactant during film formation. It was shown that desorption occurred early in the film formation process when the latex still contained around 20% of water. A small fraction of the surfactant remained irreversibly adsorbed at the particle surface. (C) 2003 Elsevier Science (USA). All rights reserved.