Highly Conductive Strong Healable Nanocomposites via Diels-Alder Reaction and Filler-Polymer Covalent Bifunctionalization

Healable stretchable conductive nanocomposites have received considerable attention. However, there has been a trade-off between the filler-induced electrical conductivity (sigma) and polymer-driven mechanical strength. Here significant enhancements in both sigma and mechanical strength by designing reversible covalent bonding of the polymer matrix and filler-matrix covalent bifunctionalization are reported. A polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene grafted with maleic anhydride forms the strong reversible covalent bonding with furfuryl alcohol through the Diels-Alder reaction. Small (7.5 nm) and medium (117 nm) nanosatellite particles are generated by in situ etching of silver flakes, enabling electron tunneling-assisted percolation. The filler-polymer covalent bifunctionalization is achieved by 3-mercaptopropanoic acid. Altogether, this results in high sigma (108 300 S m(-1)) and tensile strength (16.4 MPa), breaking the trade-off behavior. A nearly perfect (approximate to 100%) healing efficiency is achieved in both sigma and tensile strength. The conductive nanocomposite figure of merit (1.78 T Pa S m(-1)), defined by the product of sigma and tensile strength, is orders of magnitude greater than the data in literature. The nanocomposite may find applications in healable strain sensors and electronic materials.