MICROEMULSION POLYMERIZATION OF BUTYL ACRYLATE .4. EFFECT OF EMULSIFIER CONCENTRATION

The oil/water microemulsion polymerizations of butyl acrylate initiate d by a water (ammonium peroxodisulfate, APS) or oil (dibenzoyl peroxid e, DBP) soluble radical initiator at different emulsifier concentratio ns were investigated. The rate of polymerization vs. conversion curve shows two intervals. The rate of polymerization is found to decrease w ith the emulsifier concentration. This finding was discussed in terms of the decrease of both radical and monomer concentration, the chain t ransfer to emulsifier, desorption of chain-transferred radicals, and t he contribution of solution polymerization. The polymerization is fast er with APS. In the APS system the rate per particle or the number of radicals per particle increases exponentially with increasing particle size. The particle size and number increase during the whole polymeri zation. This behavior was discussed in terms of the nucleation of mono mer-containing micelles and agglomeration of primary particles during the whole polymerization. (C) 1995 John Wiley and Sons, Inc.