A Mechanochromic Hydrogen‐Bonded Rotaxane

Abstract

Tensile forces influence a variety of important biological processes and force sensors are required to study these processes in vivo. Current force sensors are often tailor‐made for a specific application, or activate at much higher forces than those observed at the cellular or tissue level. A versatile force sensor, with tunable mechanical and optical properties, activated at low pN forces will be ideal. In this communication, a new mechanoresponsive fluorescent hydrogen‐bonded rotaxane, built around a maleimide dye, is reported. Its force‐sensing properties are demonstrated in a polyacrylamide gel, a synthetic model of living tissue.

Heterocyclic Mechanophores in Polymer Mechanochemistry

“…Likewise, heterocycles with ring strains or particular electronic features can be efficient mechanophores. These include epoxides, aziridines, -lactam, 1,2-diazetidinone, bis(adamantyl)-1,2-dioxetane, naphthopyran, spiropyran (SP), spirothiopyran, [1,3]-oxazine, oxanorbornadiene, DA adduct of anthracene and phenyltriazolinedione, furan-maleimide DA adduct, and anthracene-endoperoxide (Figure 2d).…”

“…c) Mechanochemical rearrangement of naphthopyran into colored MC (tension experiment conditions: The dog-bone-shaped PDMS specimens were uniaxially stretched at a strain rate of 0.01 s -1 by two opposing actuators). d) Mechanical-force-induced rearrangement of [1,3]-oxazine into colored zwitterionic isomer (tension experiment conditions: The dog-bone-shaped PDMS specimens were uniaxially stretched by two opposing actuators at strain rates of 0.012 s -1 and 0.525 s -1 , respectively).…”

“…Figure 7 a) Mechanical force-induced rearrangement of spiropyran (SP) into merocyanine (MC) (tension experiment conditions: PDMS samples were uniaxially stretched at a strain rate of 1.5 mm s -1 by two opposing actuators).b) Mechanical force-induced rearrangement of spirothiopyran (STP) into green thiomerocyanine (TMC) (ultrasonication conditions: pulse sequence: 1 s on / 1 s off, power intensity: 8.7 W/cm 2 ; tension experiment conditions: Dumbbellshaped polyurethane specimens were uniaxially stretched at a strain rate of 0.03 s -1 by two opposing actuators) c) Mechanochemical rearrangement of naphthopyran into colored MC (tension experiment conditions: The dog-bone shaped PDMS specimens were uniaxially stretched at a strain rate of 0.01 s -1 by two opposing actuators). d) Mechanical force-induced rearrangement of[1,3] oxazine into colored zwitterionic isomer (tension experiment conditions: The dog-bone-shaped PDMS specimens were uniaxially stretched by two opposing actuators at strain rates of 0.012 s -1 and 0.525 s -1 , respectively).…”

Mechano‐Optical Response of Novel Polymer Composites Based on Elastic Polyurethane Matrix Filled with Low‐Molar‐Mass Cholesteric Droplets

“…The so‐called «optomechanical sensitivity» can be achieved by introducing force‐sensitive fluorescent dyes. These are additives such as rotaxanes, in which, upon stretching, the macrocycle is removed from the fluorophore, affecting its optical properties, [ 15–17 ] or mechanophores activated by compression to trigger a fluorogenic reaction. [ 18 ] Changes in the emission properties can be achieved by deformation of the luminescent‐dye‐doped polymer.…”

Mechanochromic Polymers

“…[10] Guillaume De Bo and co-workers report a new mechanoresponsive fluorescent hydrogen-bonded rotaxane based on a maleimide dye and demonstrate its force-sensing properties in a synthetic model of living tissue. [11] Ester Verde-Sesto, José A. Pomposo and co-workers review on techniques that can be used to manipulate and mechanically activate single-chain molecules and thus allow one to elucidate information on the stress-induced response of individual mechanophores and polymer molecules. [12] Several communications address investigations of structureproperty relations of polymer systems based on mechanochromic mechanophores.…”