Association between a sodium salt of a linear dodecylbenzene sulphonate and a non-ionic fatty alcohol ethoxylate surfactant during film formation of styrene/butadiene latex

The influence of a linear anionic dodecylbenzene sulphonate (SDBS) and a non-ionic fatty alcohol ethoxylate (AE) surfactant on the compatibility and surface morphology of a medium carboxylated styrene/butadiene latex film was established. The latex films were prepared onto a mica substrate and annealed at 80 °C for 30 min. The AFM topography and phase contrast images enabled the localization of the surfactants on the latex films. The roughness parameters calculated for the captured images were utilized in order to identify the surface characteristics and changes caused by film ageing and addition of different surfactants. Both surfactants, but especially SDBS, increased the contrast between the latex particles. Addition of a blend of AE and SDBS surfactants to the latex emulsion resulted in the formation of hydrophobic nano-sized aggregates located at latex particle–particle boundaries in the films. The formation of the aggregates is ascribed to the association between the anionic and non-ionic surfactants. The segregated anionic surfactant was randomly distributed on-top of the latex films, whereas the surfactant blend showed a highly ordered, branched texture.