Replacement of benzene with regulators for the catalyzed polymerization of1,3-butadiene to high cis-1,4-polybutadiene

The polymerization regulators mesitylene and 1,3,5-trimethoxybenzene were i nvestigated as suitable substitutes for benzene in the cobalt(II) octanoate /diethylaluminum chloride/water-catalyzed polymerization of 1,3-butadiene t o high cis-1,4-polybutadiene. The propagation rates were reduced by 50% wit h the inclusion of 18 mM mesitylene or 0.17 mM trimethoxybenzene. Mesitylen e was found to be an inefficient polymerization regulator because it reduce d the propagation rate by a combination of regulation and destruction of th e active catalyst complex. Not only did trimethoxybenzene reduce the propag ation rate by effective regulation at low concentration, it also increased the percentage activity of cobalt to 200%, indicating that two polymer chai ns were propagating simultaneously from each active center. (C) 2001 John W iley & Sons, Inc.