PRACTICAL ASPECTS OF THE EMULSIFIER-FREE EMULSION POLYMERIZATION OF STYRENE

The influences of initiator concentration, ionic strength of the aqueo us phase and styrene sulfonic acid sodium salt comonomer on the averag e particle size and particle uniformity of latexes generated via emuls ifier-free emulsion polymerization of styrene has been studied. It was found that the average particle size increased with increasing initia tor concentration in reactions where the ionic strength was not contro lled, The uniformity of the latex particles decreased as the initiator concentration increased. It was also found that at a minimum initiato r concentration of 1.5 x 10(-3) M at a temperature of 80-degrees, adeq uate conversion could not be obtained. This limited the range of parti cle sizes which could be produced without adding additional surfactant s. It was also found that smaller particles, 0.135 mum diameter, could be formed by copolymerizing styrene sulfonic acid sodium salt with st yrene. The effects of ionic strength on particle size was also investi gated and it was found that the particle size increased with increasin g ionic strength. At constant ionic strength, it was found that partic le size decreased with increasing initiator concentration as expected theoretically.