Acrylamide and butyl acrylate polymerization in Winsor IV (w/o) and Winsor I (o/w) microemulsions

The preparation of toluene-based single-phase Winsor TV water-in-oil (w/o) inverse microemulsions containing the (co)monomer couple acrylamide (AAm)/butyl acrylate (BA), their transformation to the two-phase Winsor I toil-in-water (o/w) microemulsion phase + excess of oil phase) microemulsion and homo- and (co)polymerization of(co)monomers initiated by ammonium peroxodisulfate in both types of microemulsions were studied. Increasing of the volume fraction of aqueous phase, Phi(aw), of the parent single-phase Winsor TV w/o inverse microemulsion by addition of solution of AAm in water led first only to the increase of AAm monomer concentration in inverse microemulsion, and finally to the formation of a two-phase Winsor I o/w microemulsion. Thus, Winsor TV and Winsor I microemulsions characterized with 3-fold and 6-fold higher content of AAm (i.e., up to 6 mass % in Winsor IV and 12 mass % in the microemulsion phase of Winsor I with respect to only 2 mass % in the parent Winsor IV w/o microemulsion) were obtained. Maximum rate of (co)polymerization of AAm/BA couple in Winsor IV w/o inverse microemulsion is only 1.5 times greater than that found for o/w microemulsion phase of Winsor I. Maximum homopolymerization rate of BA in toluene-based Winsor IV inverse w/o microemulsion in comparison to BA-based Winsor TV inverse w/o inverse microemulsion is only 1/75 of the maximum rate of BA homopolymerization in the latter system. The kinetic behavior of AAm and BA (co)monomer pair in free-radical polymerization in studied microemulsions was explained as a result of the different monomer partition between water and oil phases of the dispersion system, of the capability of monomer and/or oligomer radical formation in the individual phases, and of the transfer of these radicals between individual phases of the w/o and/or o/w microemulsions.