Facile UV-healable polyethylenimine-copper (C2H5N-Cu) supramolecular polymer networks

This study focuses on the development of facile polyethylenimine-copper (C2H5N-Cu) supramolecular polymer networks which upon mechanical damage are capable of reversible UV-induced self-repairs by the reformation of Cu-N coordination bonds. The chemical changes responsible for self-healing that leads to network remodeling include the formation of C2H5N-Cu complexes which, upon UV absorption, induce charge transfer between sigma(N) bonding and d(x2-y2)(Cu) antibonding orbitals. The primary structural component responsible for network remodeling is the C2H5N-Cu coordination complex center that, upon UV exposure, undergoes square-planar-to-tetrahedral (D-4h -> T-d) transition. The energy difference between d(x2-y2) and d(xz/yz) orbitals during process change decreases significantly, enabling the sigma(N) -> d(x2-y2)(Cu) charge transfer and leading to energetically favorable Cu-N geometries. Manifested by virtually no temperature changes during UV-initiated self-healing, a unique feature of this network is the high efficiency of the damage-repair cycle resulting from the reversible conversion of electromagnetic radiation to chemical energy.