Synthesis of well-defined linear-bottlebrush-linear triblock copolymer towards architecturally-tunable soft materials.

Linear-bottlebrush-linear (LBBL) triblock copolymers are emerging systems for topologically-tunable elastic materials. In this paper, a new synthetic methodology is presented to synthesize LBBL polystyrene- block -bottlebrushpolydimethylsiloxane- block -polystyrene (PS- b -bbPDMS- b -PS) triblock copolymer via the "grafting onto" approach where the precursors are individually synthesized through living anionic polymerization and selective coupling reaction. In this two-step approach, polystyrene- block -polymethylvinylsiloxane (PS- b -PMVS) diblock copolymer with a low dispersity couples with another living PS block to form PS- b -PMVS- b -PS triblock copolymer. Secondly, this is followed by grafting of separately prepared monohydride-terminated PDMS chains with controllable grafting density through a hydrosilylation reaction. In addition to fully tunable architectural parameters, this approach permits a quantitative determination of the ratio of diblock and triblock bottlebrush copolymers and consistency between batches, highlighting the feasibility for scaled-up production. These LBBL triblock copolymers self-assemble into soft, low-modulus thermoplastic elastomers, and the precise knowledge of the composition is crucial for correlating microstructure to mechanical properties.