Copolymerization of vinyl acetate with acrylic monomers in microemulsion

Composition domains corresponding to “one phase microemulsions” have been studied for the monomer mixtures consisting in vinyl acetate (VAc)–2-ethyl-hexyl acrylate (EHA) and VAc–ethyl acrylate (EtA). Maleic monoester with nonyl phenol ethoxylated with 25 mol ethylene oxide has been used as surfactant; n-propanol (n-PrOH), t-butanol (t-BuOH) and 2-ethyl-hexanol have been employed as cosurfactants. The number of microemulsions formed in the frame of the existing systems (as shown in ternary diagrams) is higher for polar monomers and cosurfactants: EtA>EHA; n-PrOH>t-BuOH. Refractometric and conductometric studies have proved the reality of three types of microemulsions: O/W, bicontinuous and W/O respectively. The homogeneous domains lessen after radical copolymerization. However, for the zone with a bicontinuous microstructure the conversion for the comonomer mixture reaches a minimum; a degradative chain transfer of the growing radicals with the cosurfactant might explain this phenomenon. It has been proved by GPC, that the concentration of unreacted surfactant increases when the concentration of the acrylic monomer increases as well.