Polymerization of acrylamide in inverse microemulsion in the presence of mixtures of oleophilic and hydrophilic surfactants

The preparation of single-phase toluene/sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Phi(alpha w) of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20 degrees C three viscosity maxima are observed. At 50 degrees C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5-8 mPa . s while the second, most prominent peak still marks the level of ca. 250 mPa . s. The polymerization of acrylamide in dispersion systems is initiated by water-soluble ammonium peroxodisulfate (APS) and oil-soluble dibenzoyl peroxide (DBP) at 60 degrees C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Phi(aw) values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Phi(aw) value of ca. 30%, irrespective of the nature of initiator. For Phi(aw) values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some signs of shallow minimum close to Phi(aw) of 50%.