DESORPTION OF THE SURFACTANT FROM THE PARTICLE SURFACE DURING LATEX FILM FORMATION

Properties of latex films are very dependent on the distribution of the surfactants in the film. It has been recognized that distribution itself depends on the desorption characteristics of the surfactant from the particle-water interface during film formation. This article deals with this problem of surfactant desorption in the particular situation of latex film formation. First, FTIR spectroscopic evidence is presented for desorption of hexadecyl pyridinium chloride (HPCl) in poly(2-ethyl hexyl methacrylate) (P2EHMA) latex films. Some consequences of desorption or non-desorption of various surfactants on the structure and properties of P2EHMA latex films are then presented. This concerns the crystallization of cationic surfactants, HPCl and hexadecyl trimethylammonium bromide (HTAB), in the films and the mechanical properties of films containing ethoxylated nonyl phenol with 10 ethoxy segments (NP10) or sodium dodecyl sulphate (SDS). In the last part, the determination of the fraction of SDS desorbing from the particle-water interface in a model poly(styrene-butyl acrylate-methacrylic acid) latex coalescing in water is described. Other methods for studying desorption are proposed.