PARTICLE GROWTH IN BUTADIENE EMULSION POLYMERIZATION .1. THE USE OF FREMY SALT AS AQUEOUS RADICAL SCAVENGER

The kinetics of the seeded emulsion polymerization of butadiene in com bination with variable Fremy salt (potassium nitrosodisulfonate) conce ntrations was investigated in order to monitor non-steady state kineti cs necessary for obtaining information on entry and exit of radicals f rom latex particles. Fremy salt is used because it is an entirely wate r-soluble stable radical that in principle can scavenge water-soluble radicals produced by a water-soluble initiator like peroxodisulfate, b ut allegedly will not interfere with radicals within lat'' particles. Adequate buffering of the pH is a prerequisite for stable Fremy salt c oncentrations in time. Emulsion polymerizations in the presence of Fre my salt showed that not all radicals in the aqueous phase of a swollen polybutadiene latex are scavenged. The use of Fremy salt to monitor n on-steady state kinetics in the seeded emulsion polymerization of buta diene in the presence of tertiary dodecyl mercaptan yields no satisfyi ng results. The use of Fremy salt seems to be restricted to systems wh ere the rate of polymerization is strongly influenced by variation in initiator concentration, i. e. the styrene system or the butadiene sys tem in the absence of tertiary dodecyl mercaptan.