Binuclear Scandium Initiators for the Syndiospecific Triblock Copolymerization of Styrene with ε‑Caprolactone

The binuclear half-sandwich scandium aminobenzyl/chloride complex [(Cp′)­Sc­(THF)­Cl]2[p-(CH2C6H3(o-NMe2)−)2] (Cp′ = C5Me4SiMe3) (2) was synthesized by linking two scandium centers through a bis­(aminobenzyl) fragment. When activated with a halide abstractor, [(Et3Si)2(μ-H)]­[B­(C6F5)4], complex 2 is capable of copolymerizing styrene and ε-caprolactone to furnish ABA-type triblock copolymers (PCL-b-sPS-b-PCL) consisting of perfectly syndiospecific polystyrene (sPS) (B) in the midblock and tunable PCL (A) content in the end blocks. The stress–strain measurements of a solution casting film of copolymers demonstrated that the triblock copolymers exhibited superior mechanical performances compared to those diblock BA copolymers (sPS-b-PCL) prepared from mononuclear scandium aminobenzyl/chloride complex [(Cp′)­Sc­(o-CH2C6H4–NMe2)­(THF)­Cl]­(1).