Latex blends of fluorinated and fluorine-free acrylates:: Emulsion polymerization and tapping mode atomic force microscopy of film formation

Latex based upon fluorinated acrylates such as perfluorooctylethyl methacrylate (FMA) and perfluorooctylethyl acrylate (FA) and fluorine-free acrylates such as n-butyl methacrylate (BMA) was prepared by means of emulsion polymerization in the presence of octadecyltrimethylammonium bromide (C(18)TAB) and 2,2'-azobis(2-amidinopropane) dihydrochloride (V50) as water-soluble azo initiator. Reaction calorimetric studies revealed that acetone addition, preferably 15-25 wt %, was the key to achieve high monomer conversion and to produce stable latex with average particle sizes varying between 50 and 300 nm. Monomer conversion was increased, and latex particle size was reduced when 2 wt % n-butyl acrylate (BA) was added together with fluorine-containing monomers. The reaction enthalpy of FMA was determined to be 62 kJ/mol with respect to 75 kJ/mol for the more reactive FA. Stable poly(perfluorooctylethyl methacrylate)/poly(n-butyl methacrylate) (PFMA/PBMA) latex blends were formed. According to tapping mode atomic force microscopy, PBMA formed a dense film at 65 degrees C containing PFMA nanoparticles dispersed in the PBMA matrix. Annealing at 100 degrees C caused accumulation of PFMA at the surface and formation of a gradient film containing a surface layer with high fluorine content. Such latex blends are of interest in water-, oil-, and soil-repellent coatings.