Mechanochemically assisted morphing of shape shifting polymers

Tang, Rui; Gao, Wenli; Jia, Yulin; Wang, Kai; Datta, Barun Kumar; Zheng, Wei; Zhang, Huan; Xu, Yuanze; Lin, Yangju; Weng, Wengui

doi:10.1039/d3sc02404k

Cited by 3 publications

(2 citation statements)

References 53 publications

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“…The activation stress thresholds of spirolactam in DN elastomers 2 and 3 are similar (3.49 vs 3.82 MPa) and located in strain-hardening regions despite their different activation strain thresholds (275 vs 350%). We conclude that spirolactam is activated during the enthalpic stretching of polymer chains, while the aggregates of PhMz-4OH are destroyed once the entropic stretching of polymer chains happens …”

Section: Resultsmentioning

confidence: 86%

Spirolactam and ESIPT in a Double-Network Elastomer: Multicolor Mechanochromism and Dual-Ratiometric Strain Sensing in Low and High Tensile Stress

Hu,

Cheng,

et al. 2024

Macromolecules

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Monitoring strain/stress in the bulk polymer material by mechanochromic mechanophores (MMs) with multimodal analyses can provide valuable information under loading. Herein, multicolor polymer mechanochromism from cyan to blue and further to purplish red and dual ratiometric strain sensing in low and high tensile stress were realized by incorporating noncovalent bond-type excited-state intramolecular proton transfer MM PhMz-4OH and covalent bond-type rhodamine MM Rh6G-2OH into the first network of a PU–PMA (polyurethane–polymethacrylate) double-network elastomer. In in situ fluorescence spectra during tensile tests, the normalized intensity of the enol emission increased linearly in low tensile stress (<275% or <3.49 MPa) and that of the rhodol emission increased linearly in high tensile stress (>275% or >3.49 MPa), which attributed to the higher activation force of spirolactam than that of PhMz-4OH disaggregation. The growth of R/G due to the ring opening of Rh6G-2OH in RGB analyses could also provide linear strain sensing under high stress. The solvent effect on polymer mechanochromism was further investigated. This strategy might provide a detailed tracking of the whole loading experience in elastomers.

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Section: Resultsmentioning

confidence: 86%

Spirolactam and ESIPT in a Double-Network Elastomer: Multicolor Mechanochromism and Dual-Ratiometric Strain Sensing in Low and High Tensile Stress

Hu,

Cheng,

et al. 2024

Macromolecules

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“…On the other hand, guidelines for molecular design to accelerate the thermal reverse reaction of HABI are still unknown and remain a challenge. Accelerating the thermal reverse reaction of HABI could improve the performance of photoinitiators and provide HABI-based self-healing polymers , and photoplastic elastomers , with fast-response capabilities. We found that the radical recombination reaction rate of compound 1 (Scheme b), in which the ortho -carbons of the phenyl groups B and C are linked by an ether bond to form a dibenzo[ b , f ]oxepine imidazole scaffold, is more than 100 times faster than that of o -Cl-HABI.…”

mentioning

confidence: 99%

Drastically Accelerated Radical Recombination Kinetics of a Hexaarylbiimidazole Derivative

Yagi,

Kawano,

Abe

2024

J. Phys. Chem. Lett.

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More than 60 years have passed since the discovery of hexaarylbiimidazole (HABI), which exhibits a characteristic photochromism that produces colored lophyl radicals through a radical dissociation reaction induced by light irradiation and reverts to its original state through a radical recombination reaction in the dark. Lophyl radicals are relatively stable among organic radicals, have low reactivity with oxygen, and have a very slow radical recombination reaction rate. HABI has been used industrially as a photoinitiator to date. However, the guidelines for molecular design to accelerate the thermal reverse reaction of HABI are still unknown and remain a challenge. We found that suppressing the rotation of the phenyl groups attached to the 4-and 5-positions of the imidazole ring of HABI is effective in accelerating the radical recombination reaction. The simple molecular design strategy to accelerate the thermal reverse reaction of HABI is expected to improve the performance of photoinitiators and photoresponsive materials that utilize HABI as a photoresponsive unit.

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Visible‐Light‐Driven Rapid 3D Printing of Photoresponsive Resins for Optically Clear Multifunctional 3D Objects

Shin,

Kwon,

Hwang

et al. 2024

Advanced Materials

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Light‐driven three‐dimensional (3D) printing is gaining significant attention for its unparalleled build speed and high‐resolution in additive manufacturing. However, extending vat photopolymerization to multifunctional, photoresponsive materials poses challenges, such as light attenuation and interference between the photocatalysts and photoactive moieties. This study introduces novel visible‐light‐driven acrylic resins that enable rapid, high‐resolution photoactive 3D printing. The synergistic combination of a cyanine‐based photocatalyst, borate, and iodonium coinitiators achieves an excellent printing rate and feature resolution under low‐intensity, red light exposure. The incorporation of novel hexaarylbiimidazole (HABI) crosslinkers allows for spatially‐resolved photoactivation upon exposure to violet/blue light. Furthermore, a photobleaching mechanism inhibited by HNu 254 during the photopolymerization process results in the production of optically‐clear 3D printed objects. Real‐time Fourier transform infrared spectroscopy validates the rapid photopolymerization of the HABI‐containing acrylic resin, whereas mechanistic evaluations reveal the underlying dynamics that are responsible for the rapid photopolymerization rate, wavelength‐orthogonal photoactivation, and observed photobleaching phenomenon. Ultimately, this visible‐light‐based printing method demonstrates: (i) rapid printing rate of 22.5 mm/h, (ii) excellent feature resolution (approximately 20 µm), and (iii) production of optically clear object with self‐healing capability and spatially controlled cleavage. This study serves as a roadmap for developing next‐generation “smart” 3D printing technologies.This article is protected by copyright. All rights reserved

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Mechanochemically assisted morphing of shape shifting polymers

Abstract: Morphing in creatures have inspired various synthetic polymer materials that are capable of shape shifting. The morphing of polymers generally relies on stimuli-active (typically heat and light active) units that...

Cited by 3 publications

References 53 publications

Spirolactam and ESIPT in a Double-Network Elastomer: Multicolor Mechanochromism and Dual-Ratiometric Strain Sensing in Low and High Tensile Stress

Spirolactam and ESIPT in a Double-Network Elastomer: Multicolor Mechanochromism and Dual-Ratiometric Strain Sensing in Low and High Tensile Stress

Drastically Accelerated Radical Recombination Kinetics of a Hexaarylbiimidazole Derivative

Visible‐Light‐Driven Rapid 3D Printing of Photoresponsive Resins for Optically Clear Multifunctional 3D Objects

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