Photoinduced multi-directional deformation of azobenzene molecular crystals

Hao, Yifei; Huang, Shuai; Guo, Yanmei; Zhou, Lina; Hao, Hongxun; Barrett, Christopher J.; Yu, Haifeng

doi:10.1039/c8tc04631j

Cited by 51 publications

(42 citation statements)

References 42 publications

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“…They attribute these photoinduced multi-directional motions to the volume change of the irradiated crystal surface at different temperatures. [42] This work demonstrated that the competition between photoisomerization and photothermal effects could affect the direction of motion under illumination.…”

Section: Reviewsmentioning

confidence: 80%

“…Very recently,Hao et al investigated photoinduced multidirectional deformations of plate-like crystals of 4-cyano-4'pentyloxy azobenzene (31;F igure 17 a). [42] The T m of trans-31 was 108 8 8Cw hile that of the cis-31 was 74-83 8 8C ( Figure 17 b,c). Since the T m gap between the two isomers is large,the temperature for photomechanical study was divided into two regions:1)below the T m of cis-31,both trans-and cismolecules are solid, and 2) above the T m of cis-31 but below the T m of trans-31, cis-31 is liquid and trans-31 remains solid.…”

Section: Reviewsmentioning

confidence: 95%

“…Reproducedf rom Ref. [42] with permission from The Royal Society of Chemistry 2018. side was liquefied by UV irradiation. At ape was pressed on all three spots.Only the liquefied spot was transferred to the tape.C ommercial transfer printing techniques are based on thermal processes.W ea chieved the transfer via ap hoto process.Because light has ahigher spatiotemporal resolution, high-resolution transfer printing techniques might be developed based on azopolymers.…”

Section: Angewandte Chemiementioning

confidence: 99%

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Photoinduced Reversible Solid‐to‐Liquid Transitions for Photoswitchable Materials

2019

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Heating and cooling can induce reversible solid‐to‐liquid transitions of matter. In contrast, athermal photochemical processes can induce reversible solid‐to‐liquid transitions of some newly developed azobenzene compounds. Azobenzene is photoswitchable. UV light induces trans‐to‐cis isomerization; visible light or heat induces cis‐to‐trans isomerization. Trans and cis isomers usually have different melting points (Tm) or glass transition temperatures (Tg). If Tm or Tg of an azobenzene compound in trans and cis forms are above and below room temperature, respectively, light may induce reversible solid‐to‐liquid transitions. In this Review, we introduce azobenzene compounds that exhibit photoinduced reversible solid‐to‐liquid transitions, discuss the mechanisms and design principles, and show their potential applications in healable coatings, adhesives, transfer printing, lithography, actuators, fuels, and gas separation. Finally, we discuss remaining challenges in this field.

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Section: Reviewsmentioning

confidence: 80%

Section: Reviewsmentioning

confidence: 95%

Section: Angewandte Chemiementioning

confidence: 99%

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Photoinduced Reversible Solid‐to‐Liquid Transitions for Photoswitchable Materials

2019

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“…Upon thermally induced crystallization to the E isomer energy in form of heat (97.1 kJ mol −1 ) is released, which is almost twice the conformational energy difference between the E and Z isomers (50 kJ mol −1 ) and provides a possible path to thermal energy storage. By setting the ambient temperature below, above, or near the melting temperature of the Z isomer of an AB crystal, multidirectional deformations could be achieved as the light‐induced change in volume within the crystal significantly depends on the aggregation state of both isomers . Besides, photochromic molecules theoretically have more than one crystallization pattern based on the isomer of the photoswitchable moieties.…”

Section: Crystalline Photoswitchable Materialsmentioning

confidence: 99%

Enlightening Materials with Photoswitches

2020

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reversible conversion between their stable and (meta)stable isomers triggered by light. The return to their native, thermo dynamically most stable isomer is gener ally induced by using another wavelength of light or simply by heat, depending on the thermal stability of the (meta)stable isomer. Retinal-the prototypical photo switch in biology-showcases impressively how structural changes occurring during a lightinduced doublebond isomerization can lead to vision or allow microorganisms to convert photons into metabolic energy. In analogy, over the years, scientists have learned that the lightdriven isomeriza tion of small molecules can be collected, possibly amplified, and transformed into macroscopic property changes, such as mechanical motion, [1] charge carrying ability, [2] assembly and disassembly of macroscopic aggregates, [3] as well as switching of surfaces and their properties. [4] Materials, which for the purpose of this review are consid ered to be solid objects or organized assemblies in solution, provide unique advantages to enhance the function of photo switches and even create new functions when compared to their standalone molecular selves (for the primarily discussed photochromic molecules herein, see Figure 1). One must, how ever, consider the inherent challenges that may present them selves when working with photoswitches in close proximity to one another. Intermolecular interactions, such as aggregation, excitation quenching, low freevolume, as well as the poten tially much higher optical density of materials can drastically lower the overall photoresponse. Yet with proper macromo lecular and supramolecular design, functions can be achieved through the incorporation of photoswitches in a material that simply cannot be obtained by an isolated molecule on its own. Here, we highlight recent examples from the literature that have appeared during the past decade since our previous review in this journal, [5] with particular focus on the order of the photos witches in relation to their environment and its impact on mate rial properties and device performance.Conceptually, one can think about maximizing a photo switching unit's effect by giving it "order" with relation to its surrounding, in particular to other switching units (Figure 2). The lowest possible order is undoubtedly demonstrated by dis persing photochromic molecules in a bulk amorphous material. If aggregation of the photoswitches can be overcome, switching units are placed in random orientation to each other giving rise to a more or less isotropic material. Starting from this scenario of randomly distributed photochromic entities, one can think about providing order in two dimensions by placing Incorporating molecular photoswitches into various materials provides unique opportunities for controlling their properties and functions with high spatiotemporal resolution using remote optical stimuli. The great and largely still untapped potential of these photoresponsive systems has not yet been fully exploited due to the fundamental challenge...

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“…In the early 2000s, photomechanical effects in dry polymer systems were significantly enhanced by the application of crosslinked liquid‐crystalline polymers (CLCPs). The success in realizing various 3D motions with CLCPs stimulated the development of other photomechanical systems such as nanocomposites, organic crystals, and supramolecules …”

Section: Introductionmentioning

confidence: 99%

Photomobile Polymer Materials with Complex 3D Deformation, Continuous Motions, Self‐Regulation, and Enhanced Processability

Ube

Ikeda

2019

Advanced Optical Materials

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Liquid‐crystalline polymers with photodeformable properties have been extensively studied due to their ability of wireless conversion of light energy into mechanical work. With the development of crosslinked liquid‐crystalline polymers, various 3D motions, such as bending, twisting, oscillation, rotation, and translational motion have been successfully induced. Recent trends for developing soft robots and microrobots accelerate the progress of photomobile polymer materials. This review is focused on recent advances in the field of photomobile materials based on liquid‐crystalline polymers. The structure–function relationship in photomobile polymer materials is overviewed, and the progress in recent years is detailed in terms of complex 3D deformation, continuous motions, self‐regulation, and processability.

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Photoinduced multi-directional deformation of azobenzene molecular crystals

Abstract: Photoinduced multi-directional deformation of azobenzene molecular crystals enabled by photoisomerization and photothermal effects.

Cited by 51 publications

References 42 publications

Photoinduced Reversible Solid‐to‐Liquid Transitions for Photoswitchable Materials

Photoinduced Reversible Solid‐to‐Liquid Transitions for Photoswitchable Materials

Enlightening Materials with Photoswitches

Photomobile Polymer Materials with Complex 3D Deformation, Continuous Motions, Self‐Regulation, and Enhanced Processability

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