Photoinduced ordering and alignment properties of polyvinylcinnamates

Bryan‐Brown, G. P.; Sage, Ian

doi:10.1080/02678299608033178

Cited by 104 publications

(63 citation statements)

References 9 publications

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“…The contrast of the TN pixels was determined by the analysis of images taken by a 10 bit digital camera. The surface anchoring energy was measured by the cell rotation method 14 under a polarizing microscope.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of liquid crystal alignment on submicron patterned surfaces

Rastegar

Škarabot

Blij

et al. 2001

Journal of Applied Physics

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The alignment mechanism of liquid crystals on polymeric surfaces that were patterned using an atomic force microscope ͑AFM͒ tip was studied by polarizing optical microscopy. Depending on the thickness of the polymer, polymer chain alignment or grooves appear to be responsible for the liquid crystal alignment. In thick polymer films ͑above 100 nm͒ the polymer chains will align in the direction of the scan due to the large lateral force exerted by the tip. In thin polymer films ͑5-20 nm͒ the polymer chains are strongly fixed to the surface and will not realign by the tip; instead grooves will be formed. The azimuthal surface anchoring the energy of thick polymer films does not depend on the scan line separation and scan force, is of the same order of magnitude as for conventionally rubbed polyimide surfaces, but increases by the number of scans. AFM patterned pixels do not show a pretilt angle.

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Section: Methodsmentioning

confidence: 99%

Mechanism of liquid crystal alignment on submicron patterned surfaces

Rastegar

Škarabot

Blij

et al. 2001

Journal of Applied Physics

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“…The polymer films containing dimerized moiety of cinnamoyl group have been investigated as a photoalignment material by many researches. 2,[6][7][8][9][10] Schadt et al have obtained the alignment film by photodimerization of cinnamoyl group in the poly(vinyl 4-methoxycinnamate). LC molecules in the LC cell were aligned perpendicular to the electric vector of the incident LPUV light.…”

mentioning

confidence: 99%

Photoreaction of New Chalcone-Based Side Chain Type Liquid Crystalline Polymers and Alignment Behavior of Liquid Crystal on the Irradiated Films

Mutoh

Tsutsumi

Koide

2002

Polym J

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ABSTRACT:We investigated the photoreaction of the side chain type liquid crystalline polymers with a chalcone derivative in the side chain. The polymer films were irradiated with linearly polarized UV (LPUV) light (350 nm) under different conditions. The photodimerization of the chalconyl moieties would mainly occur due to a decrease in the peak assigned to the chalconyl moiety by UV-vis spectroscopy measurements. The extent of the photoreaction in the liquid crystalline (LC) state is larger than that in the solid state after spin-coating and in the locked-in LC state after annealing. The LC cell was fabricated from the polymer film irradiated with LPUV light to examine the alignment properties of low molar mass LC molecules on them. A mixture of low molecular liquid crystal with the dichroic dye was filled in the LC cell. The low molecular liquid crystal was easily aligned parallel to the electric vector of the incident exposed LPUV light in the LC cell with the polymer film irradiated in the LC state.KEY WORDS Chalcone / Liquid Crystalline Polymer / Photodimerization / Photoalignment / The alignment of liquid crystalline (LC) molecules plays an important role for liquid crystalline displays (LCDs). The rubbing process has been mainly employed for the uniaxial orientation of the LC molecules. However, the rubbing process has many disadvantages for LCDs such as generation of electrostatic charge and dust. Therefore, many methods of alignment technique for LC molecules are focused on rubbing free methods. Photoalignment procedure is recognized as one of rubbing free methods and is investigated as one of candidates that overcome the generation of electrostatic charge and dust for the rubbing process. 1,2 Photoalignment procedure is based on photochemical reactions such as photoisomerization, photodimerization (photocrosslinking) and photodecomposition. With respect to photoisomerization, polymers containing an azobenzene derivative were intensively investigated. [3][4][5] The reversible photoreaction of the azobenzene moieties in the polymer induced a reversible change in the alignment direction of low molecular weight LC molecules. Generally photodimerization of photosensitive groups in the polymer was employed to obtain a stable alignment of low molecular weight LC molecules.Photodimerization of the cinnamoyl chromophore in the polymer film have been studied in detail. The polymer films containing dimerized moiety of cinnamoyl group have been investigated as a photoalignment material by many researches. 2, 6-10 Schadt et al. have obtained the alignment film by photodimerization of cinnamoyl group in the poly(vinyl 4-methoxycinnamate). LC molecules in the LC cell were aligned perpendicular to the electric vector of the incident LPUV light. 6 Alignment behavior of LC molecules would be easily improved by the liquid crystalline polymer surface where mesogenic groups are aligned. Kawatsuki et al. had reported alignment properties of side chain type liquid crystalline polymers with the cinnamoyl groups as an alignmen...

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“…Taking into account these features as well as the alignment direction of PVCN layers perpendicular to the light polarization [10][11][12][13][14][15][16] one can deduce that the transversal configuration presented in Fig. 1b is realized.…”

Section: Transverse Alignmentmentioning

confidence: 99%

“…To model these cavities we used cylindrical capillaries of 8-25 µm in diameter. The capillary walls were covered by thin layers of polyvinylcinnamate (PVCN), photoaligning polymer providing planar anchoring with the alignment direction perpendicular to polarization axis of actinic light [10][11][12][13][14][15][16]. For this purpose, PVCN was dissolved in chlorobenzene.…”

Section: Samples and Alignment Testing Methodsmentioning

confidence: 99%

Photo-Induced Orientation of Nematic Liquid Crystals in Microcapillaries

et al. 2010

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Axial and transversal orientational configurations of a nematic liquid crystal 6CHBT are realized inside glassy cylindrical capillaries by using photoalignment technique. It is demonstrated that this principle can be effectively used to enforce liquid crystal alignment in the desirable direction. It can be applied to control liquid crystal alignment in the photonic crystal fibers showing great potential for the modern telecommunication technologies.

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Photoinduced ordering and alignment properties of polyvinylcinnamates

Cited by 104 publications

References 9 publications

Mechanism of liquid crystal alignment on submicron patterned surfaces

Mechanism of liquid crystal alignment on submicron patterned surfaces

Photoreaction of New Chalcone-Based Side Chain Type Liquid Crystalline Polymers and Alignment Behavior of Liquid Crystal on the Irradiated Films

Photo-Induced Orientation of Nematic Liquid Crystals in Microcapillaries

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