Nature of stereoregular butadiene polymerization initiated by ionic coordinated catalysts

Abstract

AbstractA radioactive tracer method for distinguishing between cationic and anionic polymerization mechanism is described. The evaluation of the mechanism involves the terminating of polymerization by alkoxyl‐labeled or oxygen‐tritiated alcohols and carboxylation of active sites. The limitations of the technique were estimated by applying it to catalysts of established cationic and anionic activity. The TiI4—AlR3 was demonstrated to initiate a coordinated anionic polymerization of butadiene, whereas soluble cobalt complexes catalyze a coordinated cationic propagation. The discrepancies in results of previous studies applying alcohol termination to cobalt catalysts are interpreted. Applying the Cl36‐labeled AlR2Cl and/or CoCl2 the chlorine was demonstrated to incorporate into the polymer chain in the course of polymerization, and a mechanism is suggested involving a secondary cationic process catalyzed by excess AlR2Cl.