(163g) Isobutyronitrile Partition Between Styrene Monomer/Polymer and Water and Its Application in Miniemulsion Polymerization Initiated by Aibn

Isobutyronitrile was selected as a stable substitution of 2-cyano-2-propyl radical originating from 2,2'-azobis(isobutyronitrile) for studying radical’s behavior in miniemulsion polymerization. The partition of isobutyronitrile between (poly)styrene and water was investigated by carrying out equilibrium experiment at different conditions. Prediction from a published kinetic model with newly measured partition coefficient was also compared with published experiment data and prediction with partition coefficient of 2,2'-azobis(isobutyronitrile). It was found that the partition coefficients of isobutyronitrile were 10.98 for styrene-water system and 4.34 for polystyrene-water system, respectively, which is quite smaller than 115 of 2,2'-azobis(isobutyronitrile) in published articles. The partition coefficient was not affected by temperature, hexadecane content in the oil phase, oil/water ration and pH of the aqueous phase in styrene-water system, and by the polystyrene latex size and nature of the surfactant in polystyrene-water system. The model prediction with partition coefficient of isobutyronitrile agreed with the published experiment data well, which is evidence that the partition coefficient of primary radical should be used in theoretic calculation, but not the initiator.