DESORPTION OF EMULSIFIERS FROM POLYSTYRENE LATEXES STUDIED BY VARIOUSSURFACE TECHNIQUES - A COMPARISON BETWEEN XPS, ISS, AND STATIC SIMS

The results obtained with three surface spectroscopic methods (XPS, IS S, and static SIMS with quadrupole or time-of-flight analyzers) availa ble for the characterization of the particle surface of polystyrene la texes have been compared. The main point was to quantify the desorptio n of the surfactants used in the emulsion polymerization (Aerosol MA a nd sodium dodecylbenzenesulfonate) by the study of both unpurified and purified latexes. A comparison was made between these results and tho se obtained on a latex prepared by emulsion polymerization without any tensioactive stabilizer, therefore bearing only sulfate groups issued from the initiator. Sodium dodecyl sulfate was used as a reference fo r the presence of sulfate groups. The pure emulsifiers were also inves tigated separately. The various samples were analyzed as either powder s or films, and the results obtained on films are discussed in terms o f the migration of the surfactant toward the interface during the prep aration of the films. On the other hand, our results showed clearly th at static SIMS with a time-of-flight analyzer is the most suitable tec hnique to study the desorption of emulsifier from latex particles. The se results demonstrate that, after extensive purification by mixed-bed ion exchange resins, the strong acid emulsifier (Aerosol MA) can be c ompletely desorbed.