Polymerization of isoprene and butadiene with unparalleled stereoselectivity catalysed by rare-earth metal cationic species bearing a novel tridentate ligand

Rare-earth metal complexes bearing a novel tridentate ligand with a phenylthiol sidearm have been synthesized. The corresponding rare-earth metal cationic species, with the exception of the lutetium-based complex, showed unparalleled stereoselectivity in the polymerization of isoprene and butadiene to respectively produce cis-1,4-polyisoprene and trans-1,4-polybutadiene. The unusual reactivity ratio in the yttrium-catalyzed copolymerization of isoprene and butadiene (rIP = 2.61 and rBD = 0.57) suggested that the generated copolymer possessed a unique sequence distribution. The excellent livingness of the reactions enabled the yttrium-based catalytic system to produce isoprene-butadiene block copolymers, which could be completely hydrogenated to serve as thermoplastic elastomers. Stress-strain experiments and hysteresis testing revealed the pivotal role that the sequence length plays in determining the mechanical properties of the hydrogenated copolymers. © 2024 The Royal Society of Chemistry.