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 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 σ(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.