DISTRIBUTION OF SURFACTANTS IN LATEX FILMS

The distribution of four surfactants, namely sodium dodecyl sulfate (S DS), hexadecyl trimethylammonium (or cetyltrimethylammonium) bromide ( HTAB), hexadecylpyridinium chloride (HPCl), ethoxylated nonyl phenol c ontaining 10 or 25 ethoxy groups (NP10 and NP25), in poly(2-ethylhexyl methacrylate) (P2EHMA) latex films was studied by Fourier transform i nfrared (FTIR) spectroscopy (transmission and attenuated total reflect ion (ATR)) as a function of time, total surfactant concentration and f ilm formation conditions. The distribution is established during the d rying period of the latex and then evolves slowly in the dry film owin g to the incompatibility of the surfactant with the polymeric medium. The interfaces, film-air and film-support, can be enriched or deficien t in surfactant. In the interpretation of the results, three levels of analysis can be distinguished. The first is purely phenomenological, an intermediate level analysis goes within the film formation process and discusses the fate of the surfactant in this context, and the thir d is the most fundamental level, at which the importance of the polyme r-surfactant interactions clearly appears. Lines of research are propo sed for further improvement of the understanding of the surfactant dis tribution in latex films.