Copolymerization of vinyl acetate with acrylic monomers in microemulsion

Composition domains corresponding to "one phase microemulsions" have been s tudied for the monomer mixtures consisting in vinyl acetate (VAc)-2-ethyl-h exyl acrylate (EHA) and VAc-ethyl acrylate (EIA). Maleic monoester with non yl phenol ethoxylated with 25 mol ethylene oxide has been used as surfactan t, n-propanol (n-PrOH), t-butanol(t-BuOH) and 2-ethyl-hexanol have been emp loyed as cosurfactants, The number of microemulsions formed in the frame of the existing systems (as shown in ternary diagrams) is higher for polar mo nomers and cosurfactants: EtA > EHA: n-PrOH > t-BuOH. Refractometric and co nductometric studies have proved the reality of three types of microemulsio ns: O/W. bicontinuous and W/O respectively. The homogeneous domains lessen after radical copolymerization, However, for the zone with a bicontinuous m icrostructure the conversion fur the comonomer mixture reaches a minimum: a degradative chain transfer of the growing radicals with the cosurfactant m ight explain this phenomenon. It has been proved by GPC, that the concentra tion of unreacted surfactant increases when the concentration of the acryli c monomer increases as well. (C) 2001 Elsevier Science Ltd. All rights rese rved.