Cationic polymerization of styrene by CF3SO3H. An investigation by stopped-flow/rapid-scan spectrophotometry and rapid quenching.

The polymerization of styrene with CF₃SO₃H was studied at 30°C in dichloroethane using a stopped-flow/rapid-scan spectrophotometer. The reaction was rather simple in the early stage (up to 1 sec), the only observable absorption being that of the poly sty ryl cation (340 nm). The rate of the cation formation was approximately first order in styrene and acid concentrations. The polymer was characterized by gel-permeation chromatography of the rapid quenching product. The average degree of polymerization was 5—20 for [CF₃SO₃H], 3—10 mM and [styrene], 0.01—0.4M. The amount of the polystyryl cation formed was 1—4% of the total acid and the rate constant of propagation was estimated to be (2—4)×10⁵M⁻¹ sec⁻¹.