Photo deformation in azobenzene liquid-crystal network: Multiscale model prediction and its validation

Yun, Jung-Hoon; Li, Chenzhe; Chung, Hayoung; Choi, Joonmyung; Cho, Maenghyo

doi:10.1016/j.polymer.2015.08.013

Cited by 15 publications

(24 citation statements)

References 40 publications

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“…The specific details are described in the Supporting Information and in our previous work. 26,29 ■ RESULTS AND DISCUSSION Sample Characterization. The incorporation of azobenzene affected the phase behavior of the LC mixtures.…”

Section: T H Imentioning

confidence: 99%

“…25 As the trans−cis photoisomerization of the azobenzene changes the overall absorbance of an azo-LCP, the speed of light propagation would also be influenced, which would in turn reversely affect the speed of photoisomerization. 26 Such simultaneous interactions between the photoisomerization of azobenzene and light propagation produce a complex nonlinear light-penetration profile.…”

Section: ■ Introductionmentioning

confidence: 99%

“…There are two factors that influence the light propagation of an azo-LCP: change in absorbance during the trans–cis photochromic of azobenzene; original absorbance of the host LCP . As the trans–cis photoisomerization of the azobenzene changes the overall absorbance of an azo-LCP, the speed of light propagation would also be influenced, which would in turn reversely affect the speed of photoisomerization . Such simultaneous interactions between the photoisomerization of azobenzene and light propagation produce a complex nonlinear light-penetration profile.…”

Section: Introductionmentioning

confidence: 99%

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Light Propagation and Photoactuation in Densely Cross-Linked Azobenzene-Functionalized Liquid-Crystalline Polymers: Contribution of Host and Concerted Isomerism

Yun

Kim

et al. 2016

Macromolecules

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The photomechanical behavior of azobenzene-functionalized liquid-crystalline polymers (azo-LCPs) is closely related to UV light propagation. Here, we report the effect of light absorption by the LC host and the concerted isomerism of azobenzene on this property. In situ measurements of light absorptivity and computer simulations revealed that the light propagation of a liquid-crystalline polymer is affected by the UV absorption of the LC host under the same concerted isomerism of azobenzene. The lower UV light absorption of the LC host results in deeper UV light propagation and a sharper isomerization profile, which eventually induces faster bending when compared to the higher UV light absorption of the LC host. On the other hand, increasing the azobenzene concentration in the polymer greatly decreases the speed of light propagation, which is regarded as one of the factors inhibiting further increases in the bending speed of azo-LCP films.

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Section: T H Imentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Light Propagation and Photoactuation in Densely Cross-Linked Azobenzene-Functionalized Liquid-Crystalline Polymers: Contribution of Host and Concerted Isomerism

Yun

Kim

et al. 2016

Macromolecules

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“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In these numerous efforts, azobenzene has been used as a molecular switch to convert input light energy into conformational change which subsequently generates strain in the polymeric materials. Light is potentially a "smart" stimulus that can uniquely allow for wireless (remote) spatio-temporal control of the force or shape change.…”

mentioning

confidence: 99%

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In these numerous efforts, azobenzene has been used as a molecular switch to convert input light energy into conformational change which subsequently generates strain in the polymeric materials. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In these numerous efforts, azobenzene has been used as a molecular switch to convert input light energy into conformational change which subsequently generates strain in the polymeric materials.…”

mentioning

confidence: 99%

Photoinduced Topographical Feature Development in Blueprinted Azobenzene‐Functionalized Liquid Crystalline Elastomers

Ahn

Ware

Lee

et al. 2016

Adv Funct Materials

151

137

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5819wileyonlinelibrary.com or shape (topography). Light is potentially a "smart" stimulus that can uniquely allow for wireless (remote) spatio-temporal control of the force or shape change.A considerable volume of recent research has focused on photomechanical effects in azobenzene-functionalized liquid crystalline polymer networks (azo-LCNs) and elastomers (azo-LCEs) both experimetnally and theoretically. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In these numerous efforts, azobenzene has been used as a molecular switch to convert input light energy into conformational change which subsequently generates strain in the polymeric materials. Two related but distinguished photochemical processes have been employed including (i) transcis photoisomerization of azobenzene typically initiated with UV irradiation [ 28 ] and (ii) trans-cis-trans reorientation of azobenzene initiated with blue-green irradiation. [ 12,14,29,30 ] These photoinduced conformational changes convert input photonic energy into a mechanical output by distorting the local polymer network. Trans-cis-trans reorientation has recently been subject to intense fundamental studies focused on the athermal softening of the material at the molecular and macromolecular level. [ 30,31 ] The photogenerated strain has correspondingly been demonstrated to induce motion including bending, oscillation, and torsion. [ 19,32,33 ] For aligned azo-LCNs and azo-LCEs, the strain is anisotropic and oriented parallel to the nematic director. For example, the photogenerated strain in a monodomain (nematic) LCN results in in-plane deformation [ 29,34 ] while offsetting the orientation of the director profi le to the sample geometry results in out-of-plane deformation yielding twisting. [ 15,16,32,35,36 ] Spatial variation in the orientation (programming) of liquid crystalline monomers using surface alignment techniques such as photoalignment has many potential benefi ts. [ 32,37,38 ] In the work presented here, we employ a commercial photoalignment material also based on azobenzene. This material is formulated in solution and applied to glass substrates by spin coating, subsequently evaporating solvent, and then subjecting the surface layer to patterned linearly polarized light. The azobenzene molecules on the surface layer orient orthogonal to the electric fi eld vector of the incident linearly polarized light. Upon fi lling the cell after photoalignment, the LC monomer orients to the local surface and retains this alignment during polymerization. ). The azo-LCEs are synthesized via an orthogonal, two-step reaction between commercially available LC monomers and n -butylamine. By employing surface alignment, the local orientation of the nematic director is spatially complex ("blueprinted"). Exposing the blueprinted LCE fi lms to light as an actinic stimulus generates a photomechanical response which yields reversible shape changes between 2D and 3D shapes. The deformation of azo-LCEs strongly depends on the azobenzene concentration as well as the networ...

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Multiscale Phase Behaviors of Nematic Solids: A Short Review

Kim

Lee

et al. 2022

Multiscale Sci. Eng.

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Nematic liquid crystalline solids are novel smart materials of which mesogenic molecules are incorporated within their polymeric chains via crosslinking. The material exhibits many interesting phase behaviors and is envisaged to be harnessed as a key material of soft responsive structures that are adaptive to their surroundings. These behaviors are originated by intricate interactions between diverse phenomena ranging from molecular interactions, mesoscopic phase transition, and elasticity of macroscale. The modeling and analysis of the behavior, therefore, requires the multiscale point of view in that the vast design space of such material cannot be fully exploited otherwise. In this regard, the multiscale behaviors of the nematic solids are first visited, elucidating qualitative behaviors and research of individual physics. Further, the multiscale analysis approach applied to understand and harness the behaviors of the nematic liquid crystalline solids is then reviewed.

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Photo deformation in azobenzene liquid-crystal network: Multiscale model prediction and its validation

Cited by 15 publications

References 40 publications

Light Propagation and Photoactuation in Densely Cross-Linked Azobenzene-Functionalized Liquid-Crystalline Polymers: Contribution of Host and Concerted Isomerism

Light Propagation and Photoactuation in Densely Cross-Linked Azobenzene-Functionalized Liquid-Crystalline Polymers: Contribution of Host and Concerted Isomerism

Photoinduced Topographical Feature Development in Blueprinted Azobenzene‐Functionalized Liquid Crystalline Elastomers

Multiscale Phase Behaviors of Nematic Solids: A Short Review

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