KINETIC-STUDY OF THE LIVING CATIONIC POLYMERIZATION OF CYCLOHEXYL VINYL ETHER INITIATED BY HYDROGEN IODIDE IN THE PRESENCE OF AMMONIUM-SALTS

Kinetics of the cyclohexyl vinyl ether (CHVE) cationic polymerization, initiated by HI in the presence of ammonium salts (nBu4NX, with X = C l, Br, I), have been investigated. It has been shown that the presence of minute amounts of added salt ([nBu4NX]/[HI] less-than-or-equal-to 1%) are sufficient to induce a ''living'' process. In the same time, t he polymerization rate drastically decreases, suggesting a common ion salt effect and therefore an ionic-type polymerization mechanism. For a [nBu4NI]/[HI] ratio higher than 1%, the apparent polymerization rate constant remains invariable, up to a very high amount of salt, in agr eement with the only contribution of ion pairs. An estimate of the ion ic dissociation constant of active species and of their concentration in the polymerization medium, as well as an evaluation of k(p)+ and k( p)+/- values, accounting for kinetic data, has been made. With nBu4NCl as added salt, a halide exchange is observed with polymer ends, in ad dition to the common ion salt effect. These two processes result in a continuous decrease of the polymerization rate with an increase of the tetrabutylammonium chloride amount. The main reaction mechanisms invo lved in these polymerization systems are discussed.