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

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.