Surface composition of coalesced acrylic latex films studied by XPS and SIMS

Surface concentrations of two anionic surfactants (sodium dodecyl sulfate (SDS) and sodium dodecyl diphenyl ether disulfonate (SDED)) in coalesced acrylic latex films (methyl methacrylate and butyl acrylate copolymer, 45 55 wt%) were studied by XPS and SIMS. For SDS, surface enrichment is very pronounced and can reach saturation in the layer analyzed by XPS (∼50 Å). Film maturation for 3 months gives rise to SDS expulsion toward interfaces. For SDED, enrichment is much less pronounced and during maturation the surfactant surface concentration does not change. It has been shown that the interfaces of 3-day-old latex films were almost saturated in the layer studied by SIMS (10–15 Å), whatever the nature of surfactant, the side of the film (air or substrate), and the average concentration. These XPS-SIMS results are useful in the interpretation of adhesion properties of films.