Synthesis of ultrahigh molecular weight bottlebrush block copolymers of ω-end-norbornyl polystyrene and polymethacrylate macromonomers

Well-controlled polystyrene-polymethacrylate bottlebrush block copolymers (BBCPs) of ultrahigh molecular weight using ω-end-norbornyl polystyrene as the macromonomer for the first block were synthesized by combining living anionic polymerization (LAP) and ring-opening metathesis polymerization (ROMP). The ω-end-norbornyl polystyrene (NB-PSt), poly(tert-butyl methacrylate) (NB-PtBMA), poly(methyl methacrylate) (NB-PMMA), and poly(benzyl methacrylate) (NB-PBzMA) macromonomers (MMs) were synthesized by the LAP. The ROMP of the MMs led to poly(NB-g-St) (molecular weight, Mn = 1515 kDa, and dispersity, Ð = 1.12), poly(NB-g-tBMA) (Mn = 1470 kDa, Ð = 1.49), poly(NB-g-MMA) (Mn = 1128 kDa, Ð = 1.42), and poly(NB-g-BzMA) (Mn = 941 kDa, Ð = 1.16) bottlebrush homopolymers at degree of polymerization (DP) of 500. Synthesis of the BBCP, P(NB-g-St)-b-P(NB-g-tBMA) was well-controlled with high molecular weight and a low dispersity (Mn = 3002 kDa, Ð = 1.17) with a total DP of 976. The self-assembly of the resulting BBCP films revealed periodic lamellar morphologies with characteristic photonic crystal properties.