Mechanochromic polymers with a multimodal chromic transition: mechanophore design and transduction mechanism

Abstract

Mechanochromic polymers have been widely investigated in terms of their colour changes in response to external mechanical forces. This unique optical property can enable their use in a wide range...

Naphthopyran molecular switches and their emergent mechanochemical reactivity

“…116,234 This type of multimodal reactivity has since attracted signicant research interest motivated by the potential to enable quantitative characterization of stress and/or strain in polymeric materials through straightforward visual analysis. 235 Bis-naphthopyrans contain two naphthopyran subunits joined by a conjugated linker and are among the few classes of photochromic compounds capable of accessing distinctly colored states based on the duration or intensity of light exposure. 116,119,120,234,[236][237][238][239] Encouraged by the photochromic properties of the bisnaphthopyran photoswitches originally reported by Zhao and Carreira, 116,119,234 we designed a series of poly(methyl acrylate) polymers incorporating a bis-naphthopyran unit near the chain center for direct comparison of the photochemical and mechanochemical reactivity (Fig.…”

Multi-material 3D Printing of Mechanochromic Double Network Hydrogels for On-Demand Patterning

“…Recently, the mechanochromic materials, which can change their colors under the applied force, have drawn much attention. They could be produced by introducing the periodic structure, , the aggregation of dyes, , the incorporation of the mechanophores, − and so forth. Among them, the materials produced by incorporating the mechanophores are homogeneous, through the incorporation of the mechanophores in the polymer network, such as spiropyran, − rhodamine, − 1,2-dioxetane, − diarylbibenzofuranone, − Diels-Alder adducts, , and so forth.…”

Mechanochemical reactivity of a multimodal 2H-bis-naphthopyran mechanophore

“…Mechanochromic mechanophores possessing multiple reactive sites are theoretically capable of a more complex colorimetric response, accessing distinct states under mechanical force that are coupled to unique changes in optical properties. 20 For example, a bis-naphthopyran mechanophore previously developed in our group displays force-dependent multicolor mechanochromism due to a force-modified dynamic equilibrium that is established between two different merocyanine states. 6 In contrast to the photochemical reaction, which proceeds via sequential ring-opening reactions of each pyran unit, [21][22][23][24] mechanical activation was found to simultaneously open both pyran rings to generate the bis-merocyanine species.…”