LATEX FILM FORMATION · Investigations on the effect of reactive surfactants on latex film microstructure and properties via tracer diffusion

Aqueous film forming polymer (latex) dispersions are widely used in the adhesive and coating industry. In recent years, significant research effort is devoted to the development of reactive surfactants for emulsion polymerization, with the aim of achieving better product performance in these water-based systems. They are devised to produce emulsions with better technical properties like emulsion stability, low water uptake of dry films, and better gloss. The reactive surfactant takes part in the polymerization and becomes a part of the polymer chain, and thus modifies the film formation process, the film microstructure as well as the film properties. So far, however, a clear molecular level understanding of how reactive surfactants influence the performance of coatings is missing. Thus, studies at molecular length scales performed on well-defined model systems, where the particle surfaces are modified with covalently attached surfactants, are important to understand the film formation process and tailoring film properties. In this project a systematic study on the influence of anionic reactive surfactants on latex film formation and film properties of Poly (butyl methacrylate) emulsions, employing a tracer diffusion technique (Forced Rayleigh scattering; FRS) is proposed. Reactive surfactants avoid surfactant migration to and aggregation at the polymer-substrate and the polymer-air interface and also modify the polymer interdiffusion between particles that is necessary to form a mechanically strong film. Both effects can be studied at molecular level with the FRS technique. The benefit of the proposed studies will be an improved understanding of the relationship between the nature of the interfacial membranes (depending upon the surfactant used) and the film formation process, helpful in the advancement of the control over film properties for better performing adhesives and coatings.