Reversible Photorheological Lyotropic Liquid Crystals

Peng, Shuhua; Guo, Qipeng; Hughes, Timothy C.; Hartley, Patrick G.

doi:10.1021/la4030469

Cited by 55 publications

(73 citation statements)

References 46 publications

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“…In contrast, cis HC 4 Azo, HC 8 Azo and HC 12 Azo decreased foam life from 6.67 min to 5.12, 5.49 and 6.02 min, respectively. From the UV-Vis absorption spectra, HC n Azo showed highly sensitive photoresponse in UV light (1 s for trans / cis isomerization) regardless of the hydrophobic chain length, and in visible light, the cis / trans photo-isomerization time was increased upon increasing the hydrophobic chain length (i.e.…”

Section: Discussionmentioning

confidence: 73%

“…7, each of HC 4 Azo, HC 8 Azo and HC 12 Azo can modulate foam stability over a wide range of concentrations. 7, each of HC 4 Azo, HC 8 Azo and HC 12 Azo can modulate foam stability over a wide range of concentrations.…”

Section: Foam Control Propertiesmentioning

confidence: 95%

“…In contrast, the destabilization of the cis isomers was mainly attributed to the interfacial desorption properties. Moreover, the insoluble HC 12 Azo particles covered in the air/liquid interface or dispersed in the foam lm, aggravating foam instability. 23 The trans isomers converted into cis isomers and rapidly desorbed from the interface when the trans-rich interface was exposed to UV light.…”

Section: Foam Control Propertiesmentioning

confidence: 99%

“…7,8 Due to the large space occupation of residual foam, it is expected to be destroyed in a rapid and controlled way. 12,13 In addition, a light trigger can be accurately localized, enabling both temporal and spatial control and is easily achieved using optical lenses, lters, and masks. Switchable foam is a new strategy to rapidly destroy residual foam and re-foam in a controllable way.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability

et al. 2016

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To obtain an aqueous foam photo-switch, azobenzene molecules [4-hydroxy-4 0 -oxoalkyl azobenzene (HC n Azo) n ¼ 4, 8, and 12] were synthesized. The hydrophobic chain length affected both photoresponsive properties and foam stability controllability. trans / cis isomerization of HC n Azo occurred by exposing to UV light for 1 s and the cis / trans process for HC 4 Azo, HC 8 Azo and HC 12 Azo was carried out by visible light irradiation for 12 min, 13 min and 14 min, respectively. The reversible isomerization was repeatable, maintaining high sensitivity. Due to the small steric effect and isomerization barrier, photo-isomerization of HC 4 Azo was more rapid than HC 8 Azo and HC 12 Azo. With the increase of the hydrophobic chain length, the decrease of thermal isomerization barrier resulted in less cis isomer and more trans isomer in photo-stationary state via UV and visible light irradiation, respectively. The combination of visible light and heat can accelerate the cis / trans isomerization speed. trans HC 4 Azo, HC 8 Azo and HC 12 Azo increased foam life from 6.67 min to 10.38, 9.91 and 7.74 min, respectively, resulting from the absorption on the air-water interface and a high affinity. cis HC 4 Azo, HC 8 Azo and HC 12 Azo decreased foam life from 6.67 min to 5.12, 5.49 and 6.02 min, respectively, attributed to the interfacial desorption and increase of surface tension. HC 4 Azo with sensitive photo-isomerization and effective foam stability controllability was the best choice for an aqueous foam photo-switch.

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Section: Discussionmentioning

confidence: 73%

Section: Foam Control Propertiesmentioning

confidence: 95%

Section: Foam Control Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability

et al. 2016

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“…The intermediate compound (4‐ n ‐butyl‐4′‐hydroxyazobenzene) was synthesized according to a previously reported procedure . 4‐ n ‐Butyl‐4′‐hydroxyazobenzene (2.7 g, Scheme ), IEM (1.4 mL), and 15 mL THF were added into a round‐bottom flask fitted with a Teflon‐coated magnetic stir bar.…”

Section: Methodsmentioning

confidence: 99%

Photo‐responsive block copolymer containing azobenzene group: Synthesis by reversible addition‐fragmentation chain transfer polymerization and characterization

Yang

Liu

Chen

et al. 2019

J of Applied Polymer Sci

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The design and synthesis of a new azobenzene‐based methacrylate monomer (Azo‐IEM) was demonstrated, and its polymerization behavior during reversible addition‐fragmentation chain transfer (RAFT) polymerization was investigated. Well‐defined homopolymer and amphiphilic block copolymer containing Azo‐IEM monomeric units were successfully prepared as evidenced by NMR and GPC analysis. Moreover, the photo‐triggered reversible isomerization of polymer products in selected solvents was investigated. Finally, TEM analysis showed that there were significant differences in the nanoparticle morphologies when the block copolymer samples were irradiated with different wavelengths of light (i.e., UV and visible). The size and shapes of the p(HEMA‐b‐Azo‐IEM) polymer capable of transitions upon changes in Vis/UV light exposure which prepared from MeOH/CHCl3 mixture solvent. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47870.

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Fast‐and‐Giant Photorheological Effect in a Liquid Crystal Dimer

Aya

Szűcs

Paterson

et al. 2019

Adv Materials Inter

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stimuli, and these have been the focus of very considerable fundamental and technological interest. The potential applications of this class of materials are wide ranging including as photoresponsive adhesives, brakes, in vibration control, and in fluid-assisted polishing. In electromagneto-rheological fluids, [2][3][4][5] for example, the viscosity can be switched by -two to three orders of magnitude using either electric or magnetic fields. To date, artificial switchable materials with versatile functionality have been designed by utilizing soft matter, such as photoresponsive hydrogels, [6][7][8] polymers, [9][10][11][12][13][14][15][16] liquid crystals (LCs), [14][15][16][17][18][19][20][21][22] photo-or pH-responsive micelles, [23][24][25][26][27] and surfactants. [28] However, these materials often show a tradeoff between the contrast ratio in their viscoelastic properties and the switching speed, i.e., high switching contrast ratio in their viscoelastic properties and fast switching speeds are barely achieved simultaneously. Therefore, designing materials that exhibit good overall performance is highly challenging. To achieve such a system requires a material that exists both as a fluid and a solid and that can be switched between by external stimuli.LCs are ideal candidates for mechanically switchable systems given the large number of liquid crystalline and solid phases known to exist, and that may be tuned by molecular design to achieve self-assembled structures having a range of different length scales. For example, while the highly symmetric fluid nematic (N) phase exhibits low viscosity due to the presence of only short-range spatial order, columnar or smectic phases having lower symmetries show higher viscosities due to 1D and 2D long-range periodicities. Therefore, switching between smectic or columnar, and nematic, or isotropic phases, can result in switchable mechanical materials showing elements of high performance (see, for example, refs. [14-20]). For example, Akiyama and Yoshida [14] designed sugar alcohol derivatives with multiple azobenzene-based arms that exhibited smectic LC phases and underwent room-temperature photoinduced solidliquid transitions via the trans-cis isomerization of the azobenzene fragments. Saito et al. [19] developed anthracene-based photoresponsive columnar LC materials in which a change in molecular planarity in response to light stimuli resulted in light-induced melting. Indeed, this serves as a photoresponsive adhesive. Despite these significant advances in material design, Mechanically responsive organic materials can change their viscoelastic properties in response to external stimuli. However, materials that exhibit highly contrasting viscoelastic properties coupled with fast and reversible switching between the states involved have remained elusive. Here, it is shown that a nonsymmetric photoresponsive liquid crystal dimer exhibits photoswitching of its viscoelastic properties (shear viscosity, storage, and loss moduli) with remarkable contrast of up to 10 6 whil...

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Reversible Photorheological Lyotropic Liquid Crystals

Cited by 55 publications

References 46 publications

Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability

Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability

Photo‐responsive block copolymer containing azobenzene group: Synthesis by reversible addition‐fragmentation chain transfer polymerization and characterization

Fast‐and‐Giant Photorheological Effect in a Liquid Crystal Dimer

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