Polynorbornene‐ g ‐poly(ethylene oxide) Through the Combination of ROMP and Nitroxide Radical Coupling Reactions

Grafting‐onto and grafting‐through strategies for preparing polynorbornene‐ g ‐poly(ethylene oxide)s (PNB‐ g ‐PEO) have been developed through a combination of ring‐opening metathesis polymerization (ROMP) and nitroxide radical coupling (NRC). 2‐Bromoisobutyrate‐functionalized poly(ethylene oxide) monomethyl ether 2000 (PEO 45 ‐Br) was successfully anchored on a 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO)‐containing polynorbornene backbone of number‐average degree of polymerization ( DP n ¯ ) of 100 through the grafting‐onto strategy, resulting in PNB‐ g ‐PEO with a grafting yield ranging up to 90%. ROMP of ω‐ exo ‐norbornenyl PEO 45 monomethyl ether macromonomer issued from NRC between a nitroxide‐functionalized norbornene and PEO 45 ‐Br has allowed to reach a well‐defined bottlebrush copolymer with a backboneDP n ¯ of 100 while retaining a low dispersity of 1.09. The effect of the grafting‐onto versus grafting‐through strategy and, consequently, of the grafting density, was investigated by thermal analyses and self‐assembly properties of the PNB 100 ‐ g ‐PEO 45 . A substantial reduction of crystallinity was observed for PNB‐ g ‐PEO prepared via the grafting‐through route. Preliminary study of the self‐assembling properties has shown that the graft copolymers form monodisperse spherical particles in aqueous solution. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58 , 645–653