Norbornene-functionalized PEO- b -PCL: A versatile platform for mikto-arm star, umbrella-like, and comb-like graft copolymers

Abstract : Well-defined in-chain norbornene-functionalized poly(ethylene oxide)-b-poly(ɛ-caprolactone) copolymers (NB-PEO-b-PCL) were synthesized from a dual clickable containing both hydroxyl- and alkyne-reactive groups, namely heterofunctional norbornene 3-exo-(2-exo-(hydroxymethyl)norborn-5-enyl)methyl hexynoate. A range of NB-PEO-b-PCL copolymers were obtained using a combination of orthogonal organocatalyzed ring-opening polymerization (ROP) and click copper-catalyzed azide–alkyne cycloaddition (CuAAC). Ring-opening metathesis polymerization (ROMP) of NB-PEO-b-PCL macromonomers using ruthenium-based Grubbs’ catalysts provides comb-like and umbrella-like graft copolymers bearing both PEO and PCL grafts on each monomer unit. Mikto-arm star A2B2 copolymers were obtained through a new strategy based on thiol–norbornene photoinitiated click chemistry between 1,3-propanedithiol and NB-PEO-b-PCL. The results demonstrate that in-chain NB-PEO-b-PCL copolymers can be used as a platform to prepare mikto-arm star, umbrella-, and comb-like graft copolymers.