Nature of stereoregular butadiene polymerization initiated by ionic coordinated catalysts

Abstract

SynopsisA 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 TilrAlRa 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 Cpo-labeled AIR2Cl and/or CoC12 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 AIR,Cl.

Aspects of Mechanism of Coordination Polymerization of Conjugated Dienes

“…positive results have been obtained with both reagents (44) , and with isoprene using VCL/AIEU concentrations of tritium from labeled alcohol up to 10 4 mole per liter have been reported (31). In the latter instance, from the increase in concentration of radioactivity with time at constant polymerization rate, it seems that most of the polymer chains become attached to aluminum following chain transfer.…”

“…The same applies to 7r-allyl nickel halides, which will polymerize butadiene in alcohol solution (10). Soluble cobalt catalysts have been the subject of most work and present considerable difficulties in interpretation (44)(45)(46)(47)(48). Initial results on the AhEt iCL, Cofoctoateh system indicated alkoxyl incorporation and hence a cationic mechanism was proposed (46).…”