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Download fileMechanochemistry with Metallosupramolecular Polymers
journal contribution
posted on 2014-07-23, 00:00 authored by Diederik
W. R. Balkenende, Souleymane Coulibaly, Sandor Balog, Yoan C. Simon, Gina L. Fiore, Christoph WederThe
transduction of mechanical force into useful chemical reactions
is an emerging design approach to impart soft materials with new functions.
Here, we report that mechanochemical transductions can be achieved
in metallosupramolecular polymers. We show that both reversible and
irreversible reactions are possible and useful to create mechanically
responsive materials that display new functions. The metallopolymer
studied was a cross-linked network assembled from a europium salt
and a telechelic poly(ethylene-co-butylene) with
2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) ligands
at the termini. The Eu3+ complexes serve both as mechanically
responsive binding motifs and as built-in optical probes that can
monitor the extent of (dis)assembly due to their characteristic photoluminescent
properties. Indeed, dose-dependent and reversible metal–ligand
dissociation occurs upon exposure to ultrasound in solution. The absence
of ultrasound-induced dissociation of a low-molecular weight model
complex and in-depth studies of temperature effects confirm that the
dissociation is indeed the result of mechanical activation. The influence
of the strength of the metal–ligand interactions on the mechanically
induced dissociation was also explored. Metallopolymers in which the
Mebip ligands were substituted with more strongly coordinating dipicolinate
(dpa) ligands do not dissociate upon exposure to ultrasound. Finally,
we show that mechanochemical transduction in metallosupramolecular
polymers is also possible in the solid state. We demonstrate mending
of damaged objects through ultrasound as well as mechanochromic behavior
based on metal-exchange reactions in metallopolymers imbibed with
an auxiliary metal salt.