• Journal of Photoscience
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• v.9 no.3
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• pp.57-63
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• 2002

A homopolymer containing anthracene groups, poly[6-(9-anthryloxy)hexyl methacrylate] (PAn) was prepared and the effect of oxygen on its photochemical reaction was studied by UV and IR absorption spectroscopy in order to understand its photochemical behavior. Photochemical reaction of the PAn in THF solution under an atmosphere of air resulted in the formation of endoperoxide at the beginning stage of reaction followed by photodimerization reaction after all the oxygen was consumed, whereas photodimerization and endoperoxide formation took place concomitantly in the film state. The photoreversible reaction of the anthracene photodimer groups in the polymer by photolysis with 254 nm UV light was not efficient. The IR absorption spectral changes of the PAn film upon irradiation indicate that various photooxidation products were produced in the atmosphere of air.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.469-476
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• 2002

Photocrosslinkable soluble polyimide and polymethacrylate compound were synthesized for studying the optically induced anisotropy of the thin films. Chalcone group was introduced into the side chain unit of two polymers. We observed a photodimerization behavior between the double bonds in the chalcone group and an optical anisotropy of these materials by irradiation of a linearly polarized UV light (LPL). Optical anisotropy of the thin film was also investigated by using polarized UV absorption spectroscopy. The dynamic property of optical anisotropy in photoreactive polyimide was compared to that in polymethacrylate containing chalcone group in the side chain.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.595-599
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• 2001

The mechanisms of pretilt angle generation for a nematic liquid cystal (NLC) using a photodimerization method with obliquely polarized UV exposure on the various new photo-crosslinkable polymer were studied. A good thermal stability of all the photo-crosslinkable polymers was obtained by thermogravimetric analysis (TGA) measurement until 450$\^{C}$. High pretilt angle of the NLC was observed by polarized UV exposure on the three kinds of the photo-crosslinkable polymers containing biphenyl(BP), decyl(de), and cholesteryl(chol) group, respectively. However, the low pretilt angle of the NLC was measured by obliquely polarized UV exposure on the two kinds of the photo-crosslinkable polymers containing fluorine and chalcone group. Consequently, the high NLC angle generated is attributable to the biphenyl and alkyl moieties, and photo-dimerized chalcone group of the photopolymer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.1014-1018
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• 2003

A photoalignment material of a PGMAcr, poly[3-(acryloyloxy)-2-hydroxypropyl methacrylate] using a photopolymerized the acrylate unit by photo-initiator and a PGMA4Ch, poly[3(4-chalconyloxy)-2-hydroxypropyl methacrylate] using a photodimerization by chalcone group were synthesized. Also, the liquid crystal (LC) aligning capabilities on the photopolymer layers were studied. A good LC alignment with UV exposure on the PGMAcr surface can be obtained. However, the LC alignment defects were observed on the PGMA4Ch surface. The LC aligning capabilities of the PGMAcr surface by photo-initiator were better than that of the PGMA4Ch surface by chalcone group as photosensitive moiety.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.324-326
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• 1989

• Elastomers and Composites
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• v.45 no.4
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• pp.286-290
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• 2010

Liquid-crystalline (LC) monomer, which was functionalized with a coumarin group on their extremity, was synthesized by UV light irradiation in their LC phases. LC monomer was converted into the dimers by the cycloaddition reaction of the coumarin group, and the LC phases were maintained after photodimerization reaction. The dimers showed LC phases in the wider temperature range than those of the corresponding monomer. Structures of the compound were identified by FT IR and $^1H$ NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry (DSC), gel permeating chromatography (GPC) and polarized optical microscopy (POM). From optical polarizing microscopy, the prepared polymer shows enantiotropic liquid crystallinity with smectic and nematic textures.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.441-445
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• 2003

We synthesized three copolymers bearing photochromic spiropyran dye and chalcone moiety in the side chain for studying the dynamic properties of their photochromism. They contain methacrylate-spiropyran (MAspiropyran) and methacrylate-chalcone (MA-chalcone) with the different concentration. The photosensitivity of the newly synthesized copolymers was investigated by using UV-Vis absorption spectroscopy. We observed photodimerization and photochromic behavior under UV irradiation at the same time. The effect of photocrosslink on the rate and stability of photochromism in three copolymers was considered in this study. This study might be helpful to design photochromic materials for irreversible optical memory by virtue of photocrosslinking reaction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.137-140
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• 2000

Synthesis of a new copoly (M4Ch-ChMA), copoly ((4-methacryloyloxy) chalcone-cholestery methacrylate), with chalconyl and cholesterol moiety characteristics for photoalignment materials was investigated. Good thermal stabilities of the synthesized copolymers are confirmed by thermogravimetric analysis (TGA) measurement. The pretilt angles of the nematic liquid crystal (NLC) are reduced as UV exposure time is increased on the copolymer surfaces. A pretilt angle of 81$^{\circ}$in NLC was observed with UV exposure of 3 min on the copolymer-3 surface. The NLCs pretilt angle is attributable to increased chalcone with increasing the UV exposure time.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.806-808
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• 2006

In order to understand the origin of liquid crystal orientation on a surface of photoaligning polymer polyvinyl-fluoro-cinnamate (PVCN-F), we used FTIR, AFM, UV/Vis and XPS techniques as well as we studied the rejuvenation of the photoalignment after repeated UV exposure with mutually perpendicular polarization. We found that both photodimerization of cinnamoil moieties and their trans-cis isomerisation contribute to the light-induced anchoring on PVCN-F surface, and trans-cis isomerisation is responsible for the rejuvenation of the photoalignment.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.489-492
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• 2003

Photoalignment materials of PGMAcr, poly[3-(acryloyloxy)-2-hydroxypropyl methacrylate] using an acrylate unit photopolymerized by a photo-initiator and PGMA4Ch, poly[3- (4-ehalconyloxy)-2-hydroxypropyl methacrylate] using photodimerization by the chalcone group were synthesized. Also, the liquid crystal (LC) alignment capabilities on the photopolymer layers were studied. A good LC alignment with UV exposure on the PGMAcr surface can be obtained. However, LC alignment defects were observed on the PGMA4Ch surface. The LC alignment capability of the PGMAcr surface by the photoinitiator was better than that of the PGMA4Ch surface by the chalcone group which is a photosensitive moiety.