Monomer chain transfer in the copolymerization of styrene and butyl acrylate

Free radical chain transfer constants have been measured by copolymerizing styrene and butyl acrylate in emulsion at 60°C. Some improvements to this experimental technique are reported and estimates are given of the sensitivity of the calculated values to experimental uncertainties. Monomer chain transfer constants were found to be 1.2 × 10−4 (styrene) and 2.5 × 10−4 (butyl acrylate). The sum of the cross‐transfer constants is 2.7 × 10−4. The activation energy for chain transfer to styrene monomer is found to be 24 Kcal/mol in the 44°–60°C range.