Molar Mass Control by Diethyl Zinc in the Polymerization of Butadiene Initiated by the Ternary Catalyst System Neodymium Versatate/Diisobutylaluminum Hydride/Ethylaluminum Sesquichloride

Abstract

The polymerization of 1,3‐butadiene (BD) catalyzed by the ternary Ziegler/Natta catalyst system neodymium versatate (NdV)/diisobutylaluminum hydride (DIBAH)/ethylaluminum sesquichloride (EASC) is investigated in regard to molar mass control by diethyl zinc (ZnEt2). Within the investigated range of ratios of ZnEt2 to NdV, the features of a living polymerization with a reversible exchange of the living polybutadienyl chains between neodymium and zinc are observed. In summary, ZnEt2 can be considered as an efficient molar mass control agent, which has a negligible impact on polymerization rates. In addition to the reduction of molar masses, ZnEt2 also reduces the polydispersity (PDI) and leads to a decrease of the cis‐1,4‐content.