Association of Zn- and Mg-based Chain Transfer Agents in Coordinative Chain Transfer Polymerizations of Olefins for Enhanced Control and Activity

Abstract

Based on DFT-level computational studies, ZnEt₂ was implemented as a chain transfer agent (CTA) to promote the coordinative chain transfer (co)polymerization of ethylene for the first time with a metallocene complex of Nd. The use of ZnEt₂ in combination with Mg(nBu)1.5(nOct)0.5 compared to the use of Mg(nBu)1.5(nOct)0.5 alone, improves several key aspects of the polymerization process. When ethylene is polymerized, an increase of catalytic activities is observed and narrower molar mass distributions are obtained due to reduced β-H transfer and faster reversible chain transfer reactions. In copolymerization of ethylene with butadiene, the presence of ZnEt₂ has no impact on the polymerization process in terms of polymerization kinetics and microstructure of the final copolymer. Nevertheless, it acts as an excellent CTA. Using ZnEt₂ in combination with MesMgBr rather than Mg(nBu)1.5(nOct)0.5 enables selective chain transfer between neodymium and zinc and promotes a nearly quantitative chain-end functionalization with acyl chloride.