Abstract：Aqueous-phase radical trapper, ferric chloride, was employed to quantify the primary radical desorbed from the latex particle in miniemulsion polymerization initiated by oil-soluble initiator. It was found that the dosage of trapped radical was far more than that from the initiators dissolved in the aqueous phase, therefore, the desorbed primary radical was the main origination of effective radical rather than the radicals from the initiators dissolved in the aqueous phase. The proportion of radical trapped by FeCl3, which was not affected by the temperature, decreased with the increase of initiator dosage and latex particle size and the decrease of the FeCl3 dosage. The polymerization rate and average number of radical per particle decreased with the increase of proportion of radical trapped by FeCl3.
