Kinetics of the microemulsion polymerization of styrene with short-chain alcohols as the cosurfactant

The kinetics of styrene microemulsion polymerization stabilized by sodium dodecyl sulfate (SDS) and a series of short-chain alcohols (n-CiH2i+1OH, abbreviated as CiOH, where i = 4, 5, or 6) at 60 degreesC was investigated. Sodium persulfate was used as the initiator. The microemulsion polymerization process can be divided into two intervals: the polymerization rate (R-p) first increases to a maximum at about a 20% conversion (interval I) and thereafter continues to decrease toward the end of the polymerization (interval II). For all the SDS/CiOH-stabilized polymerization systems, R-p increases when the initiator or monomer concentration increases. The average number of free radicals per particle is smaller than 0.5. The molecular weight of the polymer produced is primarily controlled by the chain-transfer reaction. In general, the reaction kinetics for the polymerization system with C4OH as the cosurfactant behaves quite differently from the kinetics of the C5OH and C6OH counterparts. This is closely related to the different water solubilities of these short-chain alcohols and the different concentrations of the cosurfactants used in the preparation of the microemulsion. (C) 2001 John Wiley & Sons, Inc.