Stimuli-responsive flexible organic crystals

Wu, Wenbo; Chen, Kui; Wang, Ting; Wang, Na; Huang, Xin; Zhou, Lina; Wang, Zhao; Hao, Hongxun

doi:10.1039/d2tc04642c

Cited by 37 publications

(25 citation statements)

References 161 publications

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“…Smart materials capable of mechanical response to environmental stimuli offer promise for the fabrication of mechanical components used in actuation or energy-harvesting applications, including flexible electronics, displays, artificial muscles, soft robots, and others. 78 The integration of flexible fluorescent crystal materials with stimulus-responsive behavior represents an emerging field that has garnered strong attention in recent years alongside the development of flexible materials (Figure 11). 54,55,68,79−88 Furthermore, temperature plays a crucial role in the application of flexible materials, particularly at low temperatures, where maintaining good flexibility is essential.…”

Section: Stimuli-responsive Optical Waveguidesmentioning

confidence: 99%

Flexible Organic Crystals for Dynamic Optical Transmission

Lan,

Li,

Naumov

et al. 2023

Chem. Mater.

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In recent years, studies of organic optical waveguide materials have emerged as a cutting-edge research area driven by their inherent advantages, such as low optical losses, structural versatility, and attractive optical properties. Notably, organic crystals exhibiting a high refractive index and optical transparency have gained attention as prospective materials for next-generation optoelectronic devices. However, unlike viscoelastic polymers with flexible chains, organic single crystals composed of densely arranged anisotropic organic small molecules have not been considered viable as functional materials due to their mechanical rigidity and fragility. Recently, the solid-state research community has witnessed a breakthrough in developing flexible organic crystalline materials, bringing a unique class of soft yet ordered engineering materials with plasticity or elasticity poised to revolutionize the concept of organic crystalline electronics. Recent works have demonstrated the feasibility of flexible organic crystals in optical transmission and have developed a variety of elastic organic crystals with different structures and functions, opening up opportunities for the design of flexible single-crystalline electronic devices. The first elastic organic crystalline optical waveguide has been prepared by building on the elasticity and luminescent properties of such organic crystals. Subsequently, various flexible organic crystals have been discovered and reported, enabling the realization of self-doped crystal waveguides, three-dimensional optical waveguides, phosphorescent waveguides, polarization rotators, and other optical elements. Through molecular design strategies, such as the construction of π-conjugated systems and introduction of heteroatoms, as well as by employing the principles of crystal engineering, researchers have developed flexible crystalline waveguiding materials with extraordinary mechanical properties, including elastic or thermoplastic bending and stimulus-specific deformation. The applications of these optically functional flexible organic crystals have been extended to low/high-temperature environments. Furthermore, combining flexible organic crystals with inorganic/polymeric materials by self-assembly techniques has led to the development of new hybrid functional materials such as solvent-resistant-coated crystals, humidity- and temperature-responsive actuators, and magnetically controllable hybrid materials. These advancements have paved the way for novel applications of organic crystals in flexible devices, such as sensors, soft robots, and optoelectronic devices.

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Section: Stimuli-responsive Optical Waveguidesmentioning

confidence: 99%

Flexible Organic Crystals for Dynamic Optical Transmission

Lan,

Li,

Naumov

et al. 2023

Chem. Mater.

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“…Stimuli-responsive molecular crystals have recently attracted − considerable interest as a promising class of smart materials capable of generating macroscopic motions in response to external stimuli such as light, − heat, , mechanical stress, , and pH value. , Ordered molecular crystals exhibit − a rapid response to external stimuli, transducing the external energy into mechanical motions. For instance, crystals of stilbene and anthracene derivatives have been reported − to exhibit photosalient effects, where their photocycloaddition induces dynamic crystal motions of bending, curling, rolling, popping, and leaping.…”

Section: Introductionmentioning

confidence: 99%

Photosalience and Thermal Phase Transitions of Azobenzene- and Crown Ether-Based Complexes in Polymorphic Crystals

Wang,

Lin,

Bhunia

et al. 2023

J. Am. Chem. Soc.

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Stimuli-responsive molecular crystals have attracted considerable attention as promising smart materials with applications in various fields such as sensing, actuation, and optoelectronics. Understanding the structure−mechanical property relationships, however, remains largely unexplored when it comes to functionalizing these organic crystals. Here, we report three polymorphic crystals (Forms A, B, and C) formed by the non-threaded complexation of a dibenzo[18]crown-6 (DB18C6) ether ring and an azobenzene-based ammonium cation, each exhibiting distinct thermal phase transitions, photoinduced deformations, and mechanical behavior. Structural changes on going from Form A to Form B and from Form C to Form B during heating and cooling, respectively, are observed by single-crystal X-ray crystallography. Form A shows photoinduced reversible bending, whereas Form B exhibits isotropic expansion. Form C displays uniaxial negative expansion with a remarkable increase of 44% in thickness under photoirradiation. Force measurements and nanoindentation reveal that the soft crystals of Form A with a low elastic modulus demonstrate a significant photoresponse, attributed to the non-threaded molecular structure, which permits flexibility of the azobenzene unit. This work represents a significant advance in the understanding of the correlation between structure− thermomechanical and structure−photomechanical properties necessary for the development of multi-stimulus-responsive materials with tailored properties.

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“…Dynamic crystals have become a research forefront due to their potential applications in bionic robots, micromachines, smart actuators, and other smart devices. , Macroscopic effects of dynamic crystals can be expressed as mechanical motions under external stimuli including light, force, heat, electricity, and chemical agents. , As one of the important dynamic crystals, photo-driven dynamic crystals have presented many conspicuous advantages such as remotely controllable manipulation, noncontact stimulus, safety, and convenience of the light source. , In addition, densely ordered molecular packing in the crystal lattice endows them with fast response speed, efficient energy transfer, and accurate motion properties . However, unlike polymers, gels, and metals with innate flexibility, most organic crystals are brittle under external forces, which greatly restricts their applications in flexible smart materials . At present, flexible and wearable devices such as foldable displays, flexible batteries, and wearable body monitoring devices are considered as one of the important next-generation technologies in the future. , Therefore, endowing brittle crystals with flexibility is essential for the design of flexible smart devices.…”

Section: Introductionmentioning

confidence: 99%

Designing Dynamic Crystals with Multiple Flexibilities through a Cocrystal Strategy for Flexible Photo-controlled Switches

Chen,

Wu,

Zhao

et al. 2023

Crystal Growth & Design

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Endowing function crystals with flexibility can further extend their applications in the field of flexible smart devices. Herein, a brittle, photo-driven dynamic crystal was successfully modified into flexible dynamic crystals through a cocrystal strategy. The fluorescence and photo-response properties of the crystals were simultaneously improved. More importantly, the cocrystals can exhibit rare multiple flexibilities, including 2D elastic bending and twistable deformation properties, which have not been reported before for cocrystals. The mechanisms of 2D elastic bending and twistable properties were investigated through detailed crystallographic analysis, experimental tests, and theoretical calculations. It was found that the 2D elastic bending can be attributed to strong π-stacked columns connecting weak molecular interactions and herringbone molecular arrangements in the cocrystals. The twistable deformation properties are closely related to the different orientations of intermolecular interactions and molecular rotation without spatial hindrance. Finally, taking advantage of the multiple flexibilities of the cocrystals, a flexible photo-controlled switch was designed and tested.

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Stimuli-responsive flexible organic crystals

Abstract: Organic crystals possessing both flexibility and stimuli-responsive properties are attractive candidates as smart materials, namely sensors, actuators, optoelectronic devices, information storage, medical applications, and so forth. They are emerging as...

Cited by 37 publications

References 161 publications

Flexible Organic Crystals for Dynamic Optical Transmission

Flexible Organic Crystals for Dynamic Optical Transmission

Photosalience and Thermal Phase Transitions of Azobenzene- and Crown Ether-Based Complexes in Polymorphic Crystals

Designing Dynamic Crystals with Multiple Flexibilities through a Cocrystal Strategy for Flexible Photo-controlled Switches

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