Particle growth in butadiene emulsion polymerization. 1. The use of Fremy salt as aqueous radical scavenger

The kinetics of the seeded emulsion polymn. of butadiene in combination with variable Fremy salt (K nitrosodisulfonate) concns. is investigated in order to monitor non-steady state kinetics necessary for obtaining information on entry and exit of radicals from latex particles. Fremy salt is used because it is an entirely water-sol. stable radical that in principle can scavenge water-sol. radicals produced by a water-sol. initiator like peroxodisulfate, but allegedly will not interfere with radicals within latex particles. Adequate buffering of the pH is a prerequisite for stable Fremy salt concns. in time. Emulsion polymns. in the presence of Fremy salt showed that not all radicals in the aq. phase of a swollen polybutadiene latex are scavenged. The use of Fremy salt to monitor non-steady state kinetics in the seeded emulsion polymn. of butadiene in the presence of tert-dodecyl mercaptan yields no satisfying results. The use of Fremy salt seems to be restricted to systems where the rate of polymn. is strongly influenced by variation in initiator concn., i.e. the styrene system or the butadiene system in the absence of tert-dodecyl mercaptan