SPECTROSCOPIC OBSERVATION OF THE PROPAGATING SPECIES IN THE CATIONIC POLYMERIZATION OF VINYL MONOMERS.

In the reported experiments, the reaction of several vinyl aromatic monomers with CF//3SO//3H and H//2SO//4 was carried out in dichloroethane at 30 degree C. The rapid formation of the cationic species was followed by the stopped-flow method, and the transient species were identified by rapid-scan spectra and rapid quenching of the reaction mixture. The monomeric cation was formed predominantly in the reaction of 1,1-diphenylethylene and excess CF//3SO//3H; however, an indanic dimer was formed in the presence of excess diphenylethylene. The rate constant for the formation of the cationic species was (3 similar 4) multiplied by 10**3M** minus **1. sec** minus **1. On the other hand, the reaction of diphenylethylene and H//2SO//4 produced two short-lived species: the monomeric cation and, probably, a monomeric radical cation. The transient species (lifetime similar 50 msec) were similarly observed in the reaction of CF//3SO//3H with styrene, methylstyrenes, and indene. General discussion is included in the paper.