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

Abstract

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 σ(N) bonding and dx2–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 (D4h → Td) transition. The energy difference between dx2–y2 and dxz/yz orbitals during process change decreases significantly, enabling the σ(N) → dx2–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.