Microscopic kinetic events in emulsion polymerization

Experimental methods are reviewed which enable the microscopic kinetic events that underpin the formation of polymer latex particles and their subsequent growth in emulsion polymerizations to be explored. The growth of latex particles is the simpler of these two processes and considerable insight has now been gained into the mechanisms of the entry of free radicals into latex particles, the exit of free radicals therefrom, the fate of the exited free radicals and bimolecular termination events in the latex particles. Some progress has been made in modelling these processes theoretically. The formation of latex particles is a more complex phenomenon. The classical picture of latex particle formation occurring by the entry of free radicals into surfactant micelles appears to lack experimental substantiation. Particle size distribution results, which contain information about the rate of production of latex particles, imply that particles are generated by a multi-step process which involves the coagulation of immature precursor particles. A semi-quantitative theory for coagulative nucleation has been developed which predicts the general features of a broad range of nucleation phenomena