NUCLEATION IN EMULSION POLYMERIZATION - A NEW EXPERIMENTAL-STUDY .1. SURFACTANT-FREE EMULSION POLYMERIZATION OF STYRENE

The very early stages of the emulsifier-free emulsion polymerization o f styrene were investigated by on-line monitoring of the optical trans mission and the conductivity of the reaction mixture. Very careful deg assing of the reaction mixture is crucial to achieve high reproducibil ity. The higher the residual gas concentration the poorer the reproduc ibility no matter if the gas is air or nitrogen. The results lead to t he conclusions that for particle nucleation the rate of initiation in the water phase is very important and that nucleation occurs via clust er formation of water-born oligomers. With the experimental techniques employed, it was possible to investigate the conversion range from 0. 47% to 1.8%. However, it was not possible to detect a particle number maximum. Instead of a maximum, a decrease in the particle number was o bserved followed by a leveling and another increase, indicating anothe r nucleation step.