Synthesis of Multiblock Bottlebrush Copolymers with Well-Defined Arbitrary Monomer Sequences: Key Factors Influencing Catalytic Stability

Precise control of the monomer sequence along a narrow-disperse copolymer chain remains a central challenge in polymer science, especially for branched chain architectures. Here, multiblock bottlebrush copolymers (MBBCPs) with well-defined, long, arbitrary sequences are facilely synthesized through programmable living ring-opening metathesis polymerization (ROMP) using a third-generation Grubbs catalyst. The lifetime of the ruthenium species is demonstrated to be highly dependent on the temperature and monomer structure. Rapid chain propagations and long lifetimes are both achieved under appropriate conditions. This enables the synthesis of MBBCPs with up to 16 segments, such as A-[BA]7-B, along the polymer chain, while maintaining a complete monomer conversion and a good livingness. This work provides general guiding principles for addressing a significant problem of living ROMP, that is, the death of catalytic species usually occurs under monomer-starved conditions, leading to ill-defined monomer sequences. Consequently, Fibonacci sequences ABABBAB and complex sequences ABCACBA and CABDACAB are readily obtained for different applications in bioinspired materials, ultrahigh-density data storage, unusual self-assembled photonic materials, etc.