DESORBED FREE-RADICALS IN EMULSION POLYMERIZATIONS - EFFECT OF AQUEOUS-PHASE SPIN TRAP

Radical low events by desorption (exit) in seeded styrene emulsion polymerization systems are studied by observing (1) the relaxation behavior when polymerization is initiated by gamma-radiolysis and then rapidly removed from the radiation source and (2) the same radiolysis relaxation experiment with the addition of an aqueous-phase free-radical trap (Fremy's salt). The results are quantitatively consistent with desorbed free radicals being rapidly terminated by Fremy's salt before there is any opportunity for them to reenter another particle and with the transfer-diffusion model for exit. The Fremy's salt technique is a general one which should be able to be used to establish the fate of free radicals in a wide range of emulsion polymerization systems.