Living 3,4-Isoselective (Co)polymerization of Biobased β-Farnesene Catalyzed by Phosphine-Functionalized Fluorenyl Rare-Earth Metal Catalysts

Abstract

With an objective to reduce petrochemical dependency, synthesis of biobased polymers from renewable feedstocks has been widely investigated. In this study, we report that living and highly 3,4-isoselective polymerization of the biobased monomer β-farnesene (100% 3,4-, >99% mmmm) can be realized at room temperature using a phosphine-functionalized fluorenyl-ligated yttrium catalytic system with ultrahigh activity. Detailed investigations suggested that the coordinated phosphine group plays a pivotal role in the high regio- and stereoselectivity of 1-Y-catalyzed β-farnesene polymerization, and the density functional density (DFT) calculation offered important insights into the 3,4-isoselectivity. Additionally, block copolymers featuring rigid 3,4-isospecific polyisoprene blocks and amorphous 3,4-isospecific polyfarnesene blocks were successfully prepared. The morphology and mechanical properties of these elastomeric copolymers were studied by using atomic force microscopy and stress–strain experiments, respectively.