Poly(vinyl acetate) and poly(vinyl acetate-co-ethylene) latexes via dispersion polymerizations in carbon dioxide

The preparation of stable dispersions of poly(vinyl acetate) or ethylene/vinyl acetate copolymers via dispersion polymerizations in a carbon dioxide continuous phase has been investigated. The effectiveness of stabilizers of various chemical compositions and architectures was compared. Both fluorinated and siloxane-based stabilizers including homopolymers, block copolymers, and reactive macromonomers were employed. Effects of variations in the reaction temperature, pressure, stabilizer composition, stabilizer concentration, and use of cosolvents on the resulting product were investigated. A turbidimetry technique was used successfully to monitor dispersed-phase volume fractions, particle sizes, and number densities during the polymerizations and to give the final particle sizes at the end of the polymerizations. The fluorinated stabilizers gave rise to smaller particles and more stable latexes when compared to the siloxane-based stabilizers.