Effect of aqueous phase composition on particle coagulation behavior in batch emulsion polymerization of styrene

Previously, we studied the latex particle coagulation in the emulsion polymerization of n-butyl acrylate induced by an electrolyte (Colloid Polym Sci 291 (2013) 2385–2398). However, the evolution of particle size distribution vs. monomer conversion and reaction time, and the possibility for the manipulation of particle coagulation to control particle size and polydispersity were not studied. In this study, we investigated the evolution of particle size distribution vs. monomer conversion and reaction time during the emulsion polymerization of styrene. Moreover, the particle coagulation at different aqueous phase compositions was studied in details. The experimental results indicate that the particle size and polydispersity was controlled by particle coagulation, which was adjusted by varying the content of electrolyte or methanol in the aqueous phase. The final latex particle size increased in the range 89.2–265.9 nm with increasing electrolyte or methanol. The effect of aqueous phase composition on the polydispersity index (PDI) of the final latex was also considered. The PDI of the final latex reached 0.005 at an appropriate aqueous phase composition. Interestingly, the demulsification phenomenon easily occurred at electrolyte concentration > 1.2 wt% or methanol/water ratio > 30/70.