ROMP of supramolecular norbornene monomers containing β-cyclodextrin–ferrocene (/adamantane) inclusion complexes

Abstract

Through the use of N-[2′-ferrocenylformamido-ethyl]-cis-5-norbornene-exo-2,3-dicarboximide (NFc) and N-[2′-adamantylformamido-ethyl]-cis-5-norbornene-exo-2,3-dicarboximide (NAd), we report the fabrication of two novel supramolecular norbornene monomers, NFc@β-CD and NAd@β-CD, through β-cyclodextrin (β-CD)/ferrrocene(Fc)- and β-CD/adamantane (Ad)-based host–guest complexation. The formation and structure of the two monomers were verified by various techniques, such as 1H and 13C NMR, 2D NOESY, IR and UV–vis spectroscopic methods. The ROMP (ring-opening metathesis polymerization) feasibility of the two supramolecular monomers was further confirmed by the successful preparation of two homopolymers (P(NFc@β-CD) and P(NAd@β-CD)) and two diblock copolymers (PNFc-b-P(NAd@β-CD) and P(NFc@β-CD)-b-P(NAd@β-CD)). The prepared polymers were adequately analyzed using 1H and 13C NMR, IR, UV–vis, end-group analysis and GPC methods. Based on the obtained results, we believe that (1) both supramolecular monomers exhibited “living” and “controlled” ROMP reactions; (2) the β-CD/Fc and β-CD/Ad inclusion complexes were not disassembled during the ROMP reactions of the two supramolecular monomers; and (3) the functional groups of β-CD had a negligible effect on the catalytic activity of the third-generation Grubbs’ catalyst. In short, this work indicated that the direct ROMP of β-CD-containing supramolecular monomers was a feasible route for preparing supramolecular polynorbornene-based homopolymers and copolymers, and this route is expected to have great potential for the preparation of various supramolecular polynorbornenes and functional materials. Two novel supramolecular norbornene monomers were prepared according to β-cyclodextrin–ferrocene (/adamantane) host–guest interactions and exhibited both the “living” and “controlled” ROMP characteristics with the aid of the third-generation Grubbs’ catalyst for the construction of corresponding supramolecular homopolymers and diblock copolymers.