Polymer Mechanochemistry Enhanced with Mechanically Interlocked Molecules

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Mechanical force is a formidable source of energy that, with its ability to distort, bend and stretch chemical bonds, is unique in the way it activates chemical reactions. In polymer mechanochemistry, polymers are used to transduce mechanical force towards a mechanoresponsive functional group (a "mechanophore") that then undergoes a mechanochemical transformation. Although mechanical force is exceptional in its ability to promote reaction pathways that are otherwise inaccessible, it has so far been limited to transformations involving bond cleavage or rearrangements. The origin of these limitations is due to the fact that the actuating polymers have to be linked to the mechanophore to activate it, which has so far made impossible to: repetitively activate scissile mechanophores or to build molecules. A solution to that problem would be to find a way for the polymer to 'grab' the mechanophore without being covalently attached to it. Interlocked molecules, which have been instrumental in the development of molecular machines, are ideally suited for that task because their subcomponents are entangled in space but not covalently linked. As a result, they can undergo large amplitude internal displacements, such as a macrocycle shuttling along the axle of a rotaxane, which makes them attractive force actuators. In this programme, we want to demonstrate how a rotaxane architecture can be used to repetitively activate scissile mechanophores and to build molecules.