The effect of the radical structure in trialkylaluminums on cis polymerization of dienes on titanium catalyst systems

1,4-cis-polymerizations of 1,3-dienes of TiCl₄-AIR₃ catalyst systems for isoprene and on TiI₂Cl₂-AIR₃ caltalyst systems for butadiene have been investigated. AIR₃ denotes herein an organoaluminum compound (OAC) containing hydrocarbon radicals, linear of different lengths or cyclic, both saturated and unsaturated, as well as those containing O, N, or Si atoms. Neither the OAC radical structure nor the Al/Ti ratios in the range investigated have been found to influence the stereospecificities and reactivities (chain propagation constant) of the active centers. Differing activities of the catalyst systems have been established to result from the variations in the concentrations of the active centers involving <1–5% of all the Ti species. The nature of the OAC radical does not change the mode of the molecular weight distribution in the polymers obtained. An increase in the molecular weight (MW) of the polydienes produced with the use of higher-MW trialkylaluminums was provoked by an increase in the macromolecules propagation period owing to the lower constant of chain transfer to the higher-MW OAC.