A novel generation of photoactive comb-shaped polyamides for the photoalignment of liquid crystals

Ryabchun, Alexander; Bobrovsky, Alexey; Chun, Sung-Ho; Shibaev, Valéry

doi:10.1002/pola.26831

Cited by 19 publications

(9 citation statements)

References 36 publications

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“…For photoalignment of low-molecular-weight liquid crystals (L-LCs), uniaxial orientation is either parallel or perpendicular to the polarization ( E ) of LP light depending on the interaction between the L-LC and the photoalignment layers. , Photoalignment of L-LC resolves a number of shortcomings of the traditional rubbing method utilized to fabricate LC displays, such as charging and dusting of the films. Many types of photosensitive materials have been investigated to explore their photoalignment ability (e.g., cinnamates, − coumarins, − cinnamic acids, and azobenzene-containing polymers − ).…”

Section: Introductionmentioning

confidence: 99%

Molecular Orientation at the Near-Surface of Photoaligned Films Determined by NEXAFS

et al. 2014

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Because of the potential for use in display applications, photoalignment using photosensitive materials has received considerable attention. Herein, the influence of film thickness on thermally stimulated photoinduced molecular reorientation structures of photoreactive liquid crystalline polymer films at the near-surface and in bulk is investigated using near-edge X-ray absorption fine structure (NEXAFS) and polarization UV absorption spectroscopies, respectively. In films less than 90-nm thick, the uniaxial in-plane orientation order in bulk gradually decreases. In contrast, films thicker than 40 nm show a sufficient molecular orientation at the near-surface. The three-dimensional orientation structures are investigated using obliquely reoriented films fabricated by slantwise p-polarized UV light exposure. Films thicker than 40 nm display an effective slantwise orientation in bulk, but the slantwise angle at the near-surface is much smaller than that in bulk. Both the substrate− film interface and film thickness play important roles in the reorientation behavior not only in bulk but also at the near-surface of the photoalignment film.

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Section: Introductionmentioning

confidence: 99%

Molecular Orientation at the Near-Surface of Photoaligned Films Determined by NEXAFS

et al. 2014

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“…S1). Upon annealing of the photooriented film of the block copolymer pAzo 10 ‐ b ‐pPhM 80 ‐ b ‐pAzo 10 above its glass transition temperature, azobenzene‐containing fragments that produce microphases serve as “commanding surfaces”, which control orientation of phenyl benzoate groups through intermaterial dividing surface of microphases formed by azobenzene and phenyl benzoate fragments. A somewhat higher dichroism of azobenzene groups is provided by a higher ordering of the formed smectic mesophase as compared with the nematic phase of phenyl benzoate units.…”

Section: Resultsmentioning

confidence: 99%

Functionally integrated liquid crystalline photochromic triple block copolymer with locally light‐ and thermal‐controllable sub‐blocks

Bugakov

Boiko

Shibaev

2016

J Polym Sci B Polym Phys

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Photoorientation and reorientation processes induced by illumination of the samples with oppositely directed polarized light and by the thermal treatment were studied for the films of triblock copolymer pAzo 10 -b-pPhM 80 -b-pAzo 10 consisting of a nematic phenyl benzoate central subblock (PhM, DP 5 80) with two terminal smectic azobenzene sub-blocks (Azo, DP 5 10). For amorphized films of triblock copolymer, illumination with polarized light (k 5 546 nm) is shown to be by orientation of only Azo-containing groups, but upon following annealing of the film, PhM groups are adjusted to the orientation of Azo fragments. It was found, that the subsequent illumination of the block copolymer sample with oppositely directed polarized light changes the orientation of azobenzene groups, while the orientation of phenyl benzoate groups is remained unchanged. Thus, the cyclic illumination of the triblock copolymer samples by the linear polarized light and subsequent thermal treatment make it possible to control and fix orientation of azobenzene and phenyl benzoate groups located in different sub-blocks in the desired and independent manner. The comparison of these results with the data on random p(Azo 7 -ran-PhM 30 ) copolymer of the similar composition revealed, that in the random copolymer, both Azo and PhM mesogenic groups are involved in the orientational cooperative process regardless of films process treatment.

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“…Actually, by taking advantage of the high specific surface area and ultra-thin fiber diameters from ES and the instantaneous photoreaction under UV irradiation, photo crosslinking reactions can be conducted with relatively high efficiency. [31][32][33][34] In this work, an UV-assisted ES (UVAES) procedure was designed to enhance the durability of PI UFMs against organic solvents. The photochemical cross-linking of fibers was realized by utilizing a photocurable PI solution as a raw spinning source.…”

Section: Introductionmentioning

confidence: 99%

Solvent‐resistant ultrafine nonwoven fibrous membranes by ultraviolet‐assisted electrospinning of organo‐soluble photosensitive polyimide resin

Lin

Liu

Yang

et al. 2020

J of Applied Polymer Sci

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An ultraviolet‐assisted electrospinning (UVAES) method was investigated to improve the solvent stability of soluble polyimide (PI) electrospun ultrafine fibrous membranes (UFMs) to assist in the development of fibrous polymeric materials with improved resistance to harsh environmental conditions and to expand the potential applications for such soft filaments. A preimidized soluble negative photosensitive polyimide (PSPI) was synthesized via an one‐step thermal polycondensation from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 1,1′‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3′‐trifluoromethylphenyl)methane (TFMDA). The PI resin was then fabricated into UFMs by both conventional electrospinning (ES) and UVAES with N,N‐dimethylacetamide (DMAc) as the solvent. During spinning, photo crosslinking reaction occurred, accompanied by simultaneous micro‐jets of PI‐UV ultrafine fibers in the UVAES procedure. This created fibers that were thermally stable at higher than 500°C, reflection over 77% of the 457‐nm‐ wavelength light, whiteness index (WI) higher than 83, and enhanced solvent resistance in DMAc. Generally speaking, compared with the PI UFMs fabricated by conventional ES procedure, the PI‐UV UFMs obtained by the newly‐developed UVAES procedure showed much superior solvent resistance, comparable thermal stability, slightly decreased optical reflectance and WI values, and reduced fiber diameters. These properties are of great value to future applications in microelectronics and wearable technology.

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A novel generation of photoactive comb-shaped polyamides for the photoalignment of liquid crystals

Cited by 19 publications

References 36 publications

Molecular Orientation at the Near-Surface of Photoaligned Films Determined by NEXAFS

Molecular Orientation at the Near-Surface of Photoaligned Films Determined by NEXAFS

Functionally integrated liquid crystalline photochromic triple block copolymer with locally light‐ and thermal‐controllable sub‐blocks

Solvent‐resistant ultrafine nonwoven fibrous membranes by ultraviolet‐assisted electrospinning of organo‐soluble photosensitive polyimide resin

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