Synthesis of bottlebrush block copolymers from bottlebrush polystyrene and bottlebrush random copolymer of ω‐end‐norbornyl polymethacrylates and their self‐assembly

Six different bottlebrush block copolymers (BBCPs) (A‐b‐(B‐co‐C)) from bottlebrush polystyrene (A) and bottlebrush random copolymers (B‐co‐C) of polymethacrylates were synthesized through living anionic polymerization and ring‐opening metathesis polymerization. To induce the phase separation of bottlebrush polystyrene (PNB‐g‐PS) (A) and bottlebrush poly(benzyl methacrylate) (PNB‐g‐PBzMA) (C)‐based BBCP with an extremely low Flory–Huggins interaction parameter (χ), three kinds of bottlebrush polymethacrylates (B): poly(norbornene‐g‐methyl methacrylate) (PNB‐g‐PMMA), poly(norbornene‐g‐tert‐butyl methacrylate) (PNB‐g‐PtBMA), and poly(norbornene‐g‐methacrylic acid) (PNB‐g‐PMAA), respectively, were randomly combined with C. An order–disorder phase transition of the BBCPs (A‐b‐(B‐co‐C)) was observed with a change in mole ratios of PMMA, PtBMA, or PMAA to PBzMA of 25, 50, and 75% in random copolymer blocks using field‐emission scanning microscopy. While the BBCP with 25% of PMAA in the random copolymer block showed an ordered lamellar nanostructure, a disordered morphology was revealed at 75% PMAA. SEM showed that the incorporation of PtBMA and PBzMA showed better‐ordered lamellar morphologies than was the case with PMMA and PBzMA at the same mole ratios. Three kinds of bottlebrush polymethacrylates were incorporated as random copolymer blocks for phase separation of polystyrene (PS) and poly(benzyl methacrylate)‐based bottlebrush block copolymers (BBCPs) with an extremely low χ parameter. The final BBCPs displayed ordered lamellar structures at 75, 50, and 25% mole ratios of incorporated poly(methyl methacrylate), poly(tert‐butyl methacrylate), and poly (methacrylic acid) in random copolymer block, respectively, depending on the effective χ parameter of the PS and each polymethacrylate macromonomer.