the BTH and NpI. Moreover, the activation process was reversible. As soon as the
stress was released, the fluorescence of films was switched off.
As a continuous work, they reported another mechanoluminophore system taking
advantage of the supramolecular approach, which the optical signal generated could
readily be tailored by a simple and rational method (Fig. 5) [21]. Three mechanoresponsive polyurethanes containing blue-, green-, and orange-light-emitting rotaxanes
were constructed through varying only the fluorophore (i.e., pyrene, anthracene, or 4(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran) incorporated in the
crown ether cycle unit. The photoluminescence of the fluorophores in the systems
was suppressed by the NpI group when the systems were in the unactivated state,
whereas the fluorescence of each of the fluorophores was switched on and
exhibited strong optical signal upon the application of mechanical force,
suggesting that each polymer could exhibit instantly reversible, strain-dependent
on/off switching of its photoluminescence. In addition, the photoluminescence
color containing white-light-emitting of such motifs could be successfully tailored by variation of the fluorophore and also by combining several
mechanophores in one system. The results demonstrated that adaptability is a
key advantage of supramolecular approaches to construct mechanoresponsive
materials.
Fig. 3 Schematic illustration of the bistable [2]rotaxane with tunable multicolor fluorescence
features [18]. (Adapted with permission [18]. Copyright 2018, Royal Society of Chemistry)
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stress was released, the fluorescence of films was switched off.
As a continuous work, they reported another mechanoluminophore system taking
advantage of the supramolecular approach, which the optical signal generated could
readily be tailored by a simple and rational method (Fig. 5) [21]. Three mechanoresponsive polyurethanes containing blue-, green-, and orange-light-emitting rotaxanes
were constructed through varying only the fluorophore (i.e., pyrene, anthracene, or 4(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran) incorporated in the
crown ether cycle unit. The photoluminescence of the fluorophores in the systems
was suppressed by the NpI group when the systems were in the unactivated state,
whereas the fluorescence of each of the fluorophores was switched on and
exhibited strong optical signal upon the application of mechanical force,
suggesting that each polymer could exhibit instantly reversible, strain-dependent
on/off switching of its photoluminescence. In addition, the photoluminescence
color containing white-light-emitting of such motifs could be successfully tailored by variation of the fluorophore and also by combining several
mechanophores in one system. The results demonstrated that adaptability is a
key advantage of supramolecular approaches to construct mechanoresponsive
materials.
Fig. 3 Schematic illustration of the bistable [2]rotaxane with tunable multicolor fluorescence
features [18]. (Adapted with permission [18]. Copyright 2018, Royal Society of Chemistry)
112
Y. Zhou et al.