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Phase inversion of polyacrylamide based inverse-emulsions: Effect of the surfactant and monomer on postinversion equilibrium properties



The influence of the interfacial chemistry on the phase inversion of polymerized water-in-oil emulsions has been investigated. For copolymerizations of acrylamide with cationic monomers, the effect of substituting of fatty acid esters and ethoxylated fatty acid esters with ABA block type stabilizers, on the kinetics and extent of phase inversion, were examined. It was determined that the solution viscosity was a valid metric to identify the mechanism by which inversion occurs, while conductivity provided a means to quantify inversion efficiency, Therefore, the interfacial chemistry was found to influence not only the plateau value of the viscosity of the polymer solution but also its kinetics. The most suitable inversion was observed with a polymer emulsion stabilized with low block copolymer stabilizer levels in the blend (8 wt %), relative to traditional fatty acid esters and ethoxylated fatty acid esters. This provided an ultimate solution viscosity 30% higher than for a polymer synthesized under identical conditions though with higher levels of the ABA block stabilizer. Overall, the optimal formulation (8% ABA) was found to liberate 88% of the latent viscosity. Given that the options in regards to inverting surfactants can be, legislatively, limited, the present work makes a case for the selection of the interfacial composition not only for its stability during reaction, and the molecular weight of the synthesized polymer, but also for the extent and rapidity of inversion. The formulation-composition map approach provided an understanding of phase inversion applied to polymer emulsion and was a useful fingerprint to qualitatively describe the catastrophic mechanism of inversion. The surfactant affinity difference applied to a blend of surfactant was found to be a convenient formulation parameter which allowed us to locate the representative point on the map of the polymer emulsion stabilized with different surfactant blend composition. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007