DETERMINATION OF THE RATE CONSTANTS OF THE ELEMENTARY STEPS IN THE CATIONIC POLYMERIZATION OF STYRENE BY TRIFLUOROMETHANESULFONIC ACID

The cationic polymerization of styrene initiated by CF3S03H was investigated in 1, 2-dichloroethane at -1 to 30 0C by the stopped flow/rapid scan spectroscopy which was combined with the rapid quenching technique. The rate constants of the elementary steps, initiation (fe), propagation (kp), spontaneous transfer and termination (kt), and transfer to monomer (ktm), were determined at four temperatures on the basis of the time courses of the cation formation, monomer consumption, and molecular weight of the quenched polymer. The kp value varied from 5 × 104 to 2 × 105 M-1 s'1 in the temperature range studied, and kv was 100-300 s'1. The lifetime of the propagating species ranged from 5 to 100 ms. (n-Bu)4N+CF3SO3 was added as a common ion salt, but its influence on the rate constants was small. The activation energy as determined from the Arrhenius plots was 7 and 15 kcal/mol for the kp and km processes, respectively. The transfer constants ktm/kp and kt/kp were close to 0.01 at the 0-30 °C range, in agreement with those reported for the H2SO4. © 1979, American Chemical Society. All rights reserved.