Anion-Coordination Foldamer-Based Polymer Network: from Molecular Spring to Elastomer.

Foldamer is a scaled-down version of coil spring, which can absorb and release energy by conformational change. Here, polymer networks with high-density of molecular springs were developed by employing anion-coordination-based foldamers as the monomer. The coiling of the foldamer is controlled by oligourea ligands coordinating to chloride ions; subsequently, the folding and unfolding of foldamer conformations endow the polymer network with excellent energy dissipation and toughness. The mechanical performance of the corresponding polymer network shows a dramatic increase from P-L2UCl (non-folding), P-L4UCl (a full turn) to P-L6UCl (1.5 turns), in terms of strength (2.62 MPa; 14.26 Mpa; 22.93 Mpa), elongation at break (70%; 325%; 352%), Young's modulus (2.69 MPa; 63.61 Mpa; 141.50 Mpa), and toughness (1.12 MJ/m3; 21.39 MJ/m3; 49.62 MJ/m3), respectively, which are also better than those without anion centers and the non-foldamer based counterparts. Moreover, P-L6UCl shows enhanced strength and toughness than most of the molecular-spring based polymer networks.Moreover, P-L6UCl shows enhanced strength and toughness than most of the molecular-spring based polymer networks. Thus, an effective strategy for designing high-performance anion-coordination-based materials is presented in this study.