Multiresponsive supramolecular gels constructed by orthogonal metal–ligand coordination and hydrogen bonding

Macromonomers bearing tridentate 2,6-bis(1,2,3-trizol-4-yl)pyridine (BTP) ligand unit synthesized via CuAAC “click” chemistry in the middle of the chain and two ureidopyrimidinone (UPy) motifs on the ends linked to the central BTP unit via PEGs of various lengths were synthesized and used for the study of gelation both with and without the presence of Eu(III) ions. Various interesting gelation behaviors were found. Gels exhibited various multi-responsive properties, including photoluminescence, mechanoresponsive properties, self-healing abilities, thermorepsonsive properties and chemoresponsive properties. The different gelation abilities and multi-responsive properties for different systems were shown to be resulted from difference in PEG linker lengths and the introduction of orthogonal metal–ligand coordination and hydrogen bonding interactions. The selective responsiveness to different chemicals would allow the development of modular sensory systems that utilize a combination of orthogonal supramolecular interactions.