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Mechanochromic elastomers that exhibit force‐induced cross‐linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross‐linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension. [ABSTRACT FROM AUTHOR]

Keywords: electron paramagnetic resonance; mechanochromism; polymer mechanochemistry; polyurethanes; self-strengthening EN electron paramagnetic resonance mechanochromism polymer mechanochemistry polyurethanes self-strengthening 8555 8555 1 04/01/21 20210406 NES 210406 B Mechanofunctional polymers b that exhibit color change, fluorescence, and self-strengthening ability were developed by Hideyuki Otsuka et al. in their Communication on page 8406. Electron paramagnetic resonance, mechanochromism, polymer mechanochemistry, polyurethanes, self-strengthening Inside Back Cover: Segmented Polyurethane Elastomers with Mechanochromic and Self-Strengthening Functions (Angew. [Extracted from the article]

Electron paramagnetic resonance, mechanochromism, polymer mechanochemistry, polyurethanes, self-strengthening Innenrücktitelbild: Segmented Polyurethane Elastomers with Mechanochromic and Self-Strengthening Functions (Angew. Keywords: electron paramagnetic resonance; mechanochromism; polymer mechanochemistry; polyurethanes; self-strengthening EN electron paramagnetic resonance mechanochromism polymer mechanochemistry polyurethanes self-strengthening 8639 8639 1 04/01/21 20210406 NES 210406 B Mechanofunktionelle Polymere b , die einen Farbwechsel, Fluoreszenz und die Fähigkeit zur Selbstverfestigung aufweisen, werden von Hideyuki Otsuka et al. in ihrer Zuschrift auf S. 8487 vorgestellt. [Extracted from the article]

Mechanochromism, a color change induced by mechanical force, has attracted much attention in materials science, as it can be used to create stress- and damage-detecting sensors. In particular, radical-type mechanochromic molecules (mechanochromophores), which produce colored radicals upon exposure to mechanical force, enable the qualitative visualization of mechanical stress and the quantitative evaluation of the generated radical species by electron paramagnetic resonance spectroscopy. However, the sensitivity of radical-type mechanochromophores to thermal stimuli limits their range of applications. Herein, we report the radical-type mechanochromophore difluorenylsuccinonitrile (DFSN), which can be used to synthesize mechanochromic polymers via living radical polymerization techniques, as its central carbon-carbon bond exhibits high thermal stability. The obtained DFSN-centered polymers show mechanochromism and desirably high thermal resistance.