Photoinduced hole dipoles’ mechanism of liquid crystal
				photoalignment

Muravsky, Alexander; Murauski, Anatoli; Kukhta, I. N.

doi:10.1364/ao.392068

Cited by 13 publications

(16 citation statements)

References 19 publications

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“…All existing concepts of photoalignment give proportional relationship between the anchoring energy and the order parameter (or dichroic ratio) of dye chromophores in the alignment layer (Figure 3). F I G U R E 2 Azimuthal anchoring energy and dichroic ratio versus exposure dose for dipole-dipole interaction between liquid crystal (LC) and photoalignment layer 11 On investigating the alignment properties of the new photoalignment material AtA-2 (Figure 4), we have obtained an unusual dependence of the azimuthal anchoring energy on the exposure dose (Figure 1), which could not be explained from the points of existing concepts of photoalignment.…”

Section: Photo-induced Hole Dipoles' Mechanism Of Lc Photolignmentmentioning

confidence: 98%

“…Thus, the order parameter of the hole dipoles formed by the mean field at the location of the absorbed molecule of the alignment layer is close to one, P 2AL(hole) $ 1. At the same F I G U R E 5 Schematic representation of small change of the dye molecules' orientation on formation of alignment direction during photoalignment 11 time, dye molecule is not restricted to change its orientation to any direction; thus, the order parameter of dye molecules that have undergone single photon absorption is close to zero P 2AL(dye) $ 0 (Figure 6).…”

Section: Photo-induced Hole Dipoles' Mechanism Of Lc Photolignmentmentioning

confidence: 99%

“…Thus, obtained dependence of the anchoring energy on the exposure dose is in good agreement with the experiment (Figure 7). 11…”

Section: Anchoring Energy Of Alignment Layermentioning

confidence: 99%

“…The latest research explains photoinduction of strong surface anisotropic interaction of AtA-2 azo-dye layer with nematic LC via contribution of the new photo-induced hole dipoles' mechanism of LC photolignment. 10,11…”

Section: Introductionmentioning

confidence: 99%

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High anchoring photoalignment material based on new photo‐induced hole dipoles' mechanism

et al. 2021

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Flat nonprofiled surface of photoalignment AtA-2 azo-dye layer possesses simultaneously low molecular orientation anisotropy and strong azimuthal anchoring energy. We explain how flat surface of alignment layer orients nematic liquid crystal and show the existence of the new photoalignment mechanism based on photo-induced hole dipole moments in the azo-dye layer. The dependence of anchoring energy coefficient on the square of dipole moments of the alignment layer and the liquid crystal layer is formulated, grounding the idea of chemical modification of AtA-2 azo-dye with molecular dipole moment $16D to obtain novel high anchoring photoalignment material. The new AtA-0042 azo-dye with molecular dipole moment $27.5D is synthesized and experimentally verified. Strong azimuthal anchoring energy over >1.4 Â 10 À4 J/m 2 is obtained for AtA-0042 photoalignment material layer with $40 mJ/cm 2 exposure dose.

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Section: Photo-induced Hole Dipoles' Mechanism Of Lc Photolignmentmentioning

confidence: 98%

Section: Photo-induced Hole Dipoles' Mechanism Of Lc Photolignmentmentioning

confidence: 99%

“…Thus, obtained dependence of the anchoring energy on the exposure dose is in good agreement with the experiment (Figure 7). 11…”

Section: Anchoring Energy Of Alignment Layermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High anchoring photoalignment material based on new photo‐induced hole dipoles' mechanism

et al. 2021

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“…However for the case of photoalginment materials, especially azo-dyes that undergo molecular orientation upon polarized light exposure [2,3], the photoinduced birefringence of the alignment layer is significant and contributes to the angle of polarization plane rotation at light propagation through LC cell. Thus the birefringence of the alignment layer should be taken into account.…”

Section: Birefringent Alignment Layer: Theorymentioning

confidence: 99%

40.3: Effect of Birefringent Alignment Layer on Azimuthal Anchoring Energy Measurement

Muravsky

Murauski

2021

Symp Digest of Tech Papers

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Birefringent alignment layer contributes to the optics of the liquid crystal cell, which is significant for optical method of azimuthal anchoring energy measurement. We obtained analytical equation to compute the corrected value of liquid crystal twist angle subject to alignment layer retardation. The data on azimuthal anchoring energy measurements of AtA‐2 and AtA‐0042 azo‐dye photoalignment materials are obtained: above >10−4J/m2 within the wide range of exposure doses 0.04 – 5.12 J/cm2.

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Varied Alignment Methods and Versatile Actuations for Liquid Crystal Elastomers: A Review

Zhao

Zhang

2021

Advanced Intelligent Systems

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Liquid crystal elastomers (LCEs) are a class of polymer materials that can produce reversible strain responses under heat, [1,2] light, [3][4][5][6] electric field [7] (or electric induction heat), [8,9] magnetic field (or magnetic induction heat), [10,11] moisture, [12] or solvent, [13] etc. They have attracted intense attention due to their enormous potential applications in soft robots, [1,9,[14][15][16][17][18] soft actuators, [4,8,14,[19][20][21][22][23] sensors, [22,[24][25][26] artificial muscles, [27][28][29] biomedicine, [30,31] flexible electronics, [32,33] light energy collection, [34] etc.LCEs are composed of rigid mesogens and flexible polymer networks, with the result that the anisotropy of liquid crystal and the rubber elasticity of polymer network can be both shown in LCEs. [35][36][37] Induced by mechanical stress, external field, or surface effect, the long axes of the mesogens can be aligned into specific directions (expressed by the director n), and this process is called alignment. Liquid crystal polymers after alignment are chemically [38] or physically [39] crosslinked to form anisotropic monodomain (including nematic, smectic, or cholesteric) LCEs. On the contrary, LCEs are in a polydomain state with isotropy when the directors of liquid crystal domains are arranged disorderly. Triggered by the external physical or chemical stimuli, the response and deformation originated from the phase transition from a liquid crystalline phase to an isotropic phase is significantly enhanced in the monodomain LCEs. This process is macroscopically manifested as the size shrinkage of LCEs in the orientation direction. [40,41] Therefore, the orientation degree of LCEs affects the maximum deformation actuated by the external stimuli to a large extent, whereas the orientation direction of LCEs determines their macroscopic deformation direction. The programmability of the mesogen orientation lays a foundation for achieving versatile deformation actuations of LCEs. [42] Aligning the mesogen orientation and achieving versatile actuations of LCEs are always the central research objects in the field of LCEs, and have developed rapidly in recent years. However, few reviews are addressing these two important issues simultaneously.Herein, in Section 1, we briefly elucidate the relationships between the microscopic orientation structure of LCEs, external stimuli, and macroscopic deformation characteristics of LCEs. In Section 2, we introduce three types of LCE alignment methods and their basic principles, and focus on comparing their programmability toward the mesogen orientation. In Section 3, we summarize two types of actuations for LCEs on the basis of the latest development, and focus on comparing their deformation controllability. In Section 4, we propose an outlook for the future key technologies to develop versatile, precise, and fastresponsive deformation actuations for LCEs. This review aims to help people to design and prepare LCEs with programmable orientation structure and excellent actuation characteristic...

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Photoinduced hole dipoles’ mechanism of liquid crystal photoalignment

Cited by 13 publications

References 19 publications

High anchoring photoalignment material based on new photo‐induced hole dipoles' mechanism

High anchoring photoalignment material based on new photo‐induced hole dipoles' mechanism

40.3: Effect of Birefringent Alignment Layer on Azimuthal Anchoring Energy Measurement

Varied Alignment Methods and Versatile Actuations for Liquid Crystal Elastomers: A Review

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