Metallosupramolecular polymers (MSPs) offer a range of useful stimuli-responsive properties, if motifs with dynamic binding characteristics are used. We recently demonstrated that damaged MSPs based on a telechelic poly(ethylene-co-butylene) (PEB) with 2,6-bis(1'-methylbenzimidazolyl)pyridine (Bip) ligands at the termini and Zn2+ or La3+salts can be healed upon exposure to UV light. Light-heat conversion causes disengagement of the metal-ligand motifs, which leads to a decrease of the molecular weight and viscosity. This allows defects to be filled with the constituting components, which re-polymerize when the light is switched off. The same MSPs can also be applied as reversible adhesives, which permit bonding and debonding on demand. Lap joints bonded with the MSPs display an appreciable shear strength, but can be rapidly debonded upon exposure to heat or UV light. Reversible and irreversible disassembly is also possible through mechanochemical transduction in MSPs assembled from Bip-PEB-Bip and Eu(ClO4)3. The Bip- Eu3+ complexes serve as mechanically responsive motifs and their characteristic fluorescence allows monitoring the extent of (dis)assembly. Dose-dependent, reversible metal-ligand dissociation occurs upon exposure to ultrasound. This effect is also possible in the solid state and permits mending of damaged objects. Mechanochemical transduction also allowed triggering a solid-state metal-exchange reaction: When the MSP was imbibed with a solution of Fe(ClO4)2, no appreciable color change was visible, whereas ultrasonication or compression caused an irreversible color change, as a result of the formation of Fe2+ complexes with Bip-PEB-Bip.

Stimuli-responsive metallosupramolecular polymers

248th National Meeting (2014)

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