Heterobimetallic Janus Catalysts for the One-Pot Synthesis of Polar-Apolar Block Copolymers

The one-pot synthesis of apolar-polar block copolymers combining polyolefins with polyesters has been a long-standing challenge in polymer chemistry. Despite broad-reaching applications of apolar-polar block copolymers in drug delivery, compatibilisation of polymer blends and biomedical materials, their synthesis often requires multi-step protocols with multiple catalysts and several isolation and purification steps. This is a particular challenge when combining the polymerisation of non-activated α-olefins with lactones, as these two distinct polymerisation mechanisms are often incompatible. This work reports heterobimetallic Janus catalysts for orthogonal 1-hexene and ε-caprolactone polymerisation. Generated in situ, the active catalysts combine distinct Ti and Al metal centres connected by a Ti-C(H)═C(R)CH₂O-Al linker (R = Me or Bn). This approach successfully delivered poly(1-hexene)-block-poly(ε-caprolactone) copolymers with well-controlled linear block copolymer architectures, targeted molar compositions and tuneable molar mass (M_n values < 67.3 kDa, Ð = 1.47), in a one-pot reaction, an approach that was successfully extended to poly(1-octene)-block-poly(ε-caprolactone) and poly(1-decene)-block-poly(ε-caprolactone) copolymers. Overall, this work is a notable addition to the toolbox for synthesising apolar-polar block copolymers. This work demonstrates for the first time that titanium-alkenyl complexes can efficiently initiate olefin polymerisations and that heterobimetallic complexes can act as efficient bifunctional initiators for distinct polymerisation mechanisms.