| Abstract: | The inverse emulsion polymerization of aqueous solution of acrylamide in toluene has been studied at 40°C using a blend of surfactants as emulsifying system and oil soluble azo initiators. The azo compound partition between the phases has been measured and the effects of their nature and concentration on the polymerization kinetics have been investigated. The influence of other parameters on the kinetics and particle size of the inverse latex have also been investigated: the nature and amount of the emulsifier system, the stirring rate, and the presence of oil-soluble inhibitor. The particle-size analysis using electron microscopy or dynamic light-scattering methods showed the presence of two populations of particles in the initial monomer emulsion and in the final inverse latex: one with very tiny particles (20 nm diam) and the other with larger particles (80–400 nm diam) which is highly polydispersed. The average size of these large particles undergoes a sharp decrease at a certain percent conversion depending upon the stirring rate. The evolution of the particle size distribution may result from a balance between coalescence and dispersion of the emulsion droplets under the effect of prevailing shear rate due to agitation. Concerning the initiation process, the very low solubility of the azo compound in the aqueous solution, together with the effect of the stirring rate and the presence of an oil-soluble inhibitor on the polymerization kinetics lead to the conclusion that most of the initiaton originates from the capture of radicals or oligomeric radicals produced in the oil phase or in the interfacial layer. |
