Switching and Extension of a [c2]Daisy-Chain Dimer Polymer

We report the synthesis of a [c2]daisy-chain dimer via ruthenium-catalyzed ring-closing olefin metathesis. Confirmation of the interlocked nature of the structure was achieved through single-crystal X-ray diffraction analysis. The dimer could be readily switched from the bound to the unbound conformation by treatment with 3.0 equiv of KOH and subsequently reprotonated by treatment with 3.0 equiv of HPF_6. Azide functionalization of the dimer enabled incorporation in linear step-growth polymer chains using the alkyne-azide “click” reaction. Gel permeation chromatography coupled with multiangle laser light scattering analysis showed the polymers contained 22 dimers and had a radius of gyration of 14.8 nm. Acylation of the amines of the dimers sterically forced elongation of the interlocked units, and MALLS analysis of the polymer showed a 48% increase in the R_g (21.4 nm)