Terpolymerization of 3-methacryloxypropyl tris(trimethylsiloxy)silane, methacrylic acid and dimethyl octyl ammonium styrene sulfonate: determination of the reactivity ratios

Terpolymerization of 3 methacryloxypropyl tris(trimethylsiloxy)silane (MPTS), methacrylic acid (MA) and dimethyl octyl ammonium styrene sulfonate (DOASS) using azobis(isobutyronitrile) as initiator was carried out in dioxane which is the common solvent of the three monomers. The reactivity ratios for the three couples of monomers MPTS/MA, MPTS/DOASS and MA/DOASS were calculated according to the general copolymerization equation using the Finnemann–Ross, Kelen–Tüdös and Tidwell–Mortimer methods. The values of the reactivity ratios indicate that the different monomer units are randomly distributed along the chains and the compositions of the different copolymers are homogeneous. From the reactivity ratios and using the terpolymerization equations, the average compositions of the comonomers in the terpolymers were calculated. A good agreement between the experimental and theoretical compositions was observed which meant that the reactivity only depended on the terminal units for the free-radical species. The instantaneous compositions are constant at a conversion less than 70%. For a higher conversion, the probability of the formation of MPTS–MPTS–MPTS triads increases highly.