Effect of the surfactant blend composition on the properties of polymerizing acrylamide-based inverse-emulsions: characterization by small-angle neutron scattering and quasi-elastic light scattering

In this study of the inverse-emulsion homopolymerization of acrylamide, sur factant blends of traditional fatty acid esters, ethoxylated fatty acid est ers and ABA-type block copolymeric stabilizers were employed. Stable and tr ansparent inverse latices with shelf lives of over one year were generated. Particle sizes were determined using quasi-elastic light scattering and sm all-angle neutron scattering and were found to be close to the threshold tr aditionally associated with microemulsions (100 nm). The turbidity of the p olymer latices and the changes in viscosity during the polymerization are a lso similar to that observed in inverse-microemulsions. The radii of gyrati on calculated from SANS data were observed to be consistent with the hydrod ynamic radius determined by QELS for the final polymerized products. SANS m easurements of the inverse-emulsions at different reaction coordinates reve aled a decrease in droplet diameters with conversion, with particles best d escribed using a polydisperse spherical core + shell model. The decrease in droplet diameter with conversion has been attributed to a surfactant rearr angement in the interfacial sheath due to the consumption of surface active acrylamide. (C) 1999 Elsevier Science Ltd. All rights reserved.