Amplified photo-responses in sequentially polymerized azobenzene-containing polymer networks: the role of isomer interconnection

Li, Chenzhe; Kim, Hyun-Su; An, Jongwon; Cho, Maenghyo

doi:10.1039/c9py01825e

Cited by 5 publications

(2 citation statements)

References 47 publications

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“…Light-induced long-lived deformation could be recovered on-demand through heating . Cho et al reported a one-pot synthesis method based on two-step sequential thiol–ene reactions for preparing azo-LCEs . In the first step, block-length-controlled azobenzene prepolymers (azo-prepolymers) were prepared in situ in a molten reaction mixture using the nucleophile-catalyzed chemoselective thiol-Michael reaction.…”

Section: Introductionmentioning

confidence: 99%

Mechano-Actuated Light-Responsive Main-Chain Liquid Crystal Elastomers

2021

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Herein, a highly mechano-actuated light-responsive main-chain liquid crystal elastomer (LCE) was prepared using the two-stage thiol−acrylate Michael addition−photopolymerization (TAMAP) method with a reactive mesogenic mixture. This reactive mixture included a newly synthesized azobenzenecontaining diacrylate reactive mesogen 4,4′-di(4-(acrylolylhexyloxy) benzoyloxy) azobenzene (D6OA), which exhibited a long mesogenic structure around the azobenzene bond. The monodomain main-chain azobenzene-containing LCE (M azo-LCE) film was prepared by mechanical drawing and visible-light curing the polydomain azo-LCE (P azo-LCE) film synthesized using the TAMAP method. M azo-LCE film showed approximately 30% contraction in length because of the trans-to-cis isomerization caused by ultraviolet (UV) irradiation, but it did not exhibit response to visible light because the long mesogenic structure of D6OA has a high energy barrier with respect to the cis-to-trans isomerization caused by visible light. However, the simple mechanical drawing of the M azo-LCE film induced the cis-to-trans isomerization. The alternating UV irradiation and mechanical drawing resulted in reversible trans-to-cis and cis-to-trans isomerizations for more than 10 cycles. The cis-to-trans/trans-to-cis isomerization and structural changes during UV irradiation and mechanical drawing were investigated via Raman spectroscopy and wide-and small-angle X-ray scatterings using a synchrotron radiation source. The azobenzene-containing chains in the layer were changed such that the staggered chains with extended trans isomers in the tilted layer (smectic C) were transformed into the chains with kinked cis isomers in the parallel-packed layer via UV irradiation, which were back to the original staggered extended chains with extended trans isomers in the tilted layer through mechanical drawing. The cisto-trans isomerization via mechanical drawing can be attributed to the location of the azobenzene linkage in the main-chain backbone, but this has been rarely reported. The high actuation and simple recovery of the main-chain M azo-LCEs provide many application possibilities in various fields such as robotics, prosthetics, microfluids, data storage, and surface relief gratings.

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Section: Introductionmentioning

confidence: 99%

Mechano-Actuated Light-Responsive Main-Chain Liquid Crystal Elastomers

2021

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“…Similar to thermosalient effects, the related jumping crystals are often referred to as the photosalient crystals. [37,91] The photoresponsive crystals in many cases occur with photochemical reactions, such as dimerization, [92][93][94][95] polymerization, [96,97] isomerization, [98] and ring closing and opening (Table 2). [99] Some of them are based on photoresponsive molecules or coordination complexes containing photoresponsive moieties, such as azobenzene, [100] diarylethene, [101,102] Schiff base, [103] and anthracene.…”

Section: Photomechanical Energy Conversionmentioning

confidence: 99%

Energy Conversion in Single‐Crystal‐to‐Single‐Crystal Phase Transition Materials

Zheng

Jia

et al. 2021

Advanced Energy Materials

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Single‐crystal‐to‐single‐crystal (SCSC) phase transitions are direct structural evolutions of crystalline materials in the solid state without the damage of ordering in the crystal lattice. These multidimensional SCSC phase transition materials are responsive to multiple external stimuli (heat, light, mechanical force, electricity, etc.), and have therefore demonstrated promising applications in many fields such as sensors, actuators, artificial muscles, soft robotics, and energy harvesting. The directionality and cooperativity of intermolecular interactions in crystal structures together with a sustained and long‐range dynamics, and the fact that they can operate at high frequency, enable fast and efficient energy conversion processes in SCSC phase transition materials. In this review, the SCSC phase transition materials are analyzed by dividing them into different types of energy transformation, from the point of view of different stimuli that initiate and drive the phase transition, including the thermo‐, photo‐, electric‐, and mechanic‐induced energy transformation, and the dimensionality dependent characteristics in these processes are presented. Moreover, the state‐of‐the‐art design and fabrication of the SCSC phase transition materials as well as the mechanisms of their energy conversion processes are discussed. Finally, the challenges and future potentials are also discussed.

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