Construction of muscle-like metallo-supramolecular polymers from a pillar[5]arene-based [c2]daisy chain

A muscle-like metallo-supramolecular polymer based on a solvent-driven [c2]daisy chain has been prepared from an amino-modified pillar[5]arene. The integration of terpyridine moieties on both ends of the [c2]daisy chain and the stiff architecture of pillar[5]arene units facilitated the efficient formation of the metallo-supramolecular polymer. UV/vis absorption spectroscopy, dynamic light scattering, transmission electron microscopy and scanning electron microscopy were used to characterize the self-assembly behavior of the resulting polymer chains. From proton NMR studies, we confirmed that the pillar[5]arene-based [c2]daisy chain could change its length continuously in response to changes in the polarity of the solvent. Consequently, the metallo-supramolecular polymer could change its length continuously according to the solvent polarity based on the individual contraction or extension of each daisy chain repeating unit. The current system can serve as a platform to mimic the muscle movement.