Stress evaluation in polymeric materials
is important in order
to not only spot danger in them before serious failure, but also precisely
interpret the destructive mechanism, which can improve the lifetime
and durability of polymeric materials. Here, we are able to visualize
stress by color changes, as well as quantitatively estimate the stress
in situ, in segmented polyurethane elastomers with diarylbibenzofuranone-based
dynamic covalent mechanophores. We prepared films of the segmented
polyurethanes, in which the mechanophores were incorporated in the
soft segments, and efficiently activated them by mechanical force.
Cleavage of the mechanophores during uniaxial elongation and their
recovery after the removal of the stress were quantitatively evaluated
by in situ electron paramagnetic resonance measurements, accompanied
by drastic color changes.
Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading.
Mit Diarylbibenzofuranon‐Einheiten quervernetzte Polymere wurden durch Polyaddition synthetisiert. Der Bindungsaustausch der Gele und ihre makroskopische Selbstheilung wurden an Luft bei Raumtemperatur im Dunkeln erreicht. Die makroskopische Verbindung komplett getrennter Teile war erfolgreich (siehe Bild).
We report the preparation of amphiphilic block copolymer micelles with dynamic covalent bonds as autonomously exchangeable crosslinkers with high tolerance against oxygen. Diarylbibenzofuranone (DABBF) was employed as a crosslinker owing to its durability to oxygen and autonomous exchangeability at ambient temperature. It was confirmed that the amphiphilic block copolymer containing the DABBF unit has the capability to form micelles and can form a crosslinking with an exchangeable structure in the presence of oxygen.
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