Abstract
The effect of the irreversible addition-fragment chain transfer agent, butyl(2-phenylallyl)sulfane (BPAS), on the course of the emulsion polymerization of styrene and on the product molecular weight was investigated. The emulsion polymerizations were performed using various amounts of sodium dodecyl sulfate (SDS) as the surfactant and potassium peroxodisulfate (KPS) as the initiator. The relationships between the rates of polymerization ((R-p) and the number of particles per volume (N-c) with respect to the concentrations of KPS, SDS, and BPAS were found to be R-p infinity[KPS](0.29), N-c infinity[KPS](0.26), R-p infinity[SDS](0.68), N-c infinity[SDS](0.72), and R-p infinity[BPAS](-0.73). The obtained relationships can be attributed to the exit of the leaving group radicals on BPAS from the polymer particles. The experimental values of the average number of radicals per particle ((n) over bar) were strongly dependent on the BPAS concentration and were in good agreement with the theoretical values ((n) over bar (theo)) from model calculations. The number-average molecular weight ((M) over bar (n)) can be controlled by BPAS over nearly the entire conversion range, which is also in agreement with the mathematical model. In addition, the transfer rate coefficient (k(tr)) of BPAS can be estimated as 326 L/mol/s at 70 degrees C. Moreover, similar good results were found for the tested redox reactions at 30 degrees C.