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 (PEO45-Br) was successfully anchored on a 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-containing polynorbornene backbone of number-average degree of polymerization (DPn) of 100 through the grafting-onto strategy, resulting in PNB-g-PEO with a grafting yield ranging up to 90%. ROMP of.-exo-norbornenyl PEO45 monomethyl ether macromonomer issued from NRC between a nitroxide-functionalized norbornene and PEO45-Br has allowed to reach a well-defined bottlebrush copolymer with a backbone DPn of 100 while retaining a low dispersity of 1.09. The effect of the grafting-onto versus graftingthrough strategy and, consequently, of the grafting density, was investigated by thermal analyses and self-assembly properties of the PNB100-g-PEO45. 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. (c) 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 645-653