Determination of rate constants of initiation and propagation in the cationic polymerization of α‐methylstyrene with CF3SO3H and H2SO4

Abstract

AbstractThe polymerization of α‐methylstyrene with CF3SO3H and H2SO4 as initiators was studied at 30°C in dichloroethane by the stopped‐flow/rapid‐scan spectroscopic technique. The propagating cation shows λmax at 336–340 nm. The initiation process and the early stage of propagation were analyzed kinetically on the basis of the cation formation and monomer consumption by taking into account the equilibrium monomer concentration. The rate of initiation with CF3SO3H was found to be proportional to the concentrations of CF3SO3H and monomer, but the initiation with H2SO4 is not proportional to the H2SO4 concentration. The rate constant of initiation was estimated to be (2 ± 1)·103 1.mol−1.s−1 with CF3SO3H, and similar values were found with H2SO4. The rate constant of propagation is 3.104 1.mol−1.s−1 with CF3SO3H as initiator and 106 − 107 1.mol−1.s−1 with H2SO4 as initiator. These kp values are close to that obtained previously in the radiation polymerization. Finally, λmax values of the propagating cation, obtained by the stopped‐flow technique, were collected.