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Kang, Hyo,Kwon, Ki-Sun,Kang, Daeseung,Lee, Jong-Chan Wiley - VCH Verlag GmbH & Co. KGaA 2007 Macromolecular Chemistry and Physics Vol.208 No.17
<P>We synthesized a series of polystyrene derivatives containing coumarin side groups using polymer analogous reactions. The liquid-crystal (LC) alignment director for these polymer films was found to be perpendicular to the rubbing direction. The contrast ratio and anchoring-energy values of these polystyrene derivatives were found to be much greater than those of polystyrene and poly(chloromethylstyrene), indicating that the coumarin side groups increase the aligning ability. For example, the anchoring energy of a polymer with 82 mol-% of coumarin-containing monomeric units, compared to polystyrene, is about 7 × 10<SUP>−5</SUP> J · m<SUP>−2</SUP> and 1 × 10<SUP>−7</SUP> J · m<SUP>−2</SUP>, respectively.</P><P> <img src='wiley_img/10221352-2007-208-17-MACP200700270-gra001.gif' alt='wiley_img/10221352-2007-208-17-MACP200700270-gra001'> </P>
Liquid crystal alignment properties of 2-naphthoxymethyl-substituted polystyrenes
Kang, Hyo,Park, Jin Seol,Kang, Daeseung,Lee, Jong-Chan Taylor Francis 2009 Liquid crystals Vol.36 No.5
<P> The liquid crystal (LC) alignment properties of LC cells fabricated with films of 2-naphthoxymethyl-substituted polystyrenes with different contents of naphthoxymethyl side groups were investigated. The polymer films exhibited good optical transparency in the visible light region (400-700 nm). The LC cells made from the unrubbed films of polymers having more than 57 mol% of 2-naphthoxymethyl containing monomeric units showed homeotropic LC alignment with a high pretilt angle of about 90o. Good electro-optical characteristics, such as the threshold voltage, response time, voltage holding ratio and residual DC voltage were observed for the LC cells fabricated with the polymer having 100 mol% of 2-naphthoxymethyl containing monomeric units as an LC alignment layer.</P>
4-Alkylphenoxymethyl-Substituted Polystyrenes for Liquid Crystal Alignment Layers
Kang, Hyo,Kim, Tae-Ho,Kang, Daeseung,Lee, Jong-Chan WILEY-VCH Verlag 2009 Macromolecular Chemistry and Physics Vol.210 No.11
<P>We synthesized a phenoxymethyl-substituted polystyrene (PHP) and a series of 4-alkylphenoxymethyl-substituted polystyrenes, where the alkyl group is &n.bond;(CH<SUB>2</SUB>)<SUB>n</SUB>H (n = 1, 2, 4, 6, and 8), using polymer analogous reactions, in order to study the effect of the phenoxymethyl and 4-alkylphenoxymethyl side groups on the liquid crystal (LC) alignment properties. The LC cell fabricated with the rubbed PHP film exhibited homogeneous planar and perpendicular LC alignment with respect to the rubbing direction. On the contrary, the LC cells made from the 4-alkylphenoxymethyl-substituted polystyrenes showed homeotropic LC alignment behaviors even at a very high rubbing density of 250, regardless of the length of the alkyl groups. Previously, n-alkylsulfonylmethyl-substituted polystyrenes with alkyl groups having more than 8 carbons (n > 8) showed homeotropic LC alignment behavior. Therefore, the additional phenoxy group in the side chain was found to improve the homeotropic LC aligning ability of the polystyrene derivatives.</P><P> <img src='wiley_img/10221352-2009-210-11-MACP200900009-gra001.gif' alt='wiley_img/10221352-2009-210-11-MACP200900009-gra001'> </P> <B>Graphic Abstract</B> <P>Phenoxymethyl-substituted polystyrene and 4-alkylphenoxymethyl-substituted polystyrenes were synthesized using polymer analogous reactions of poly-(chloromethylstyrene) with phenol and 4-alkylphenols, respectively. The planar LC alignment on phenoxymethyl-substituted polystyrene film was observed. While all of the LC cells made from the 4-alkylphen oxymethyl-substituted polystyrene films showed homeotropic LC alignment behavior and their LC cells produced high pretilt angle of about 90°. The 4-alkylphen- oxymethyl-substituted polystyrenes having good solubility in many organic solvents and low process temperature can be candidate for LC alignment layer in the flexible display. <img src='wiley_img/10221352-2009-210-11-MACP200900009-content.gif' alt='wiley_img/10221352-2009-210-11-MACP200900009-content'> </P>
Liquid crystal alignment properties of n-alkylsulphonylmethyl-substituted polyoxyethylenes
Kang, Hyo,Sohn, Eun-Ho,Kang, Daeseung,Lee, Jong-Chan Taylor Francis 2009 Liquid crystals Vol.36 No.8
<P> The liquid crystal (LC) alignment properties of LC cells fabricated with films of n-alkylsulphonylmethyl-substituted polyoxyethylenes (#S-PEO, # = 4, 6, 7, 8 and 10), where # is the number of carbon atoms in the n-alkyl side groups having different n-alkyl chain length, were investigated as a function of the rubbing density. The LC cells made from unrubbed #S-PEO (# ≥8) films having more than eight carbon atoms in the n-alkyl side groups showed homeotropic LC alignment. The homeotropic LC alignment behaviour correlated well with the surface energy values of the unrubbed #S-PEO films; homeotropic LC alignment was observed when the surface energy values of the unrubbed #S-PEO films were smaller than about 21.62 mJ m-2. The LC cells made from rubbed #S-PEO (# ≥7) films having more than seven carbon atoms with a rubbing density of 150 showed homeotropic LC alignment. It was also found that the tilt angle of the LCs on the rubbed #S-PEO films was affected not only by the n-alkyl chain length of the polymers, but also by the rubbing density, regardless of the surface energy value of the #S-PEO film.</P>
승용 연료전지 차량의 하중 특성 연구를 위한 주행시험 및 차량 동역학 해석
강종수(Jongsu Kang),김기훈(Gihoon Kim),강우종(Woojong Kang),김대성(Daeseung Kim),김용민(Yongmin Kim) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The test vehicle was reworked considering the position and weight of the main parts in the fuel cell vehicle. Driving tests were carried out in the PG of KATECH after many sensors were attached in the vehicle. As result, wheel force and strains at frame are measured. The acquired data was also analyzed to compare the characteristic of gasoline and fuel cell vehicle. Multi-body dynamics model of the full vehicle was constructed to extract and compare the loads of main position. As one of the applications of the virtual model, simple impact and driving simulations have been carried out between the vehicle model and a salient road. The impact load and reaction load at the mounting points of components was extracted for the verification of the safety of tile component.
모듈 내구시험시 Wheel Adapter의 중량 영향성 평가
강종수(Jongsu Kang),김기훈(Gihoon Kim),강우종(Woojong Kang),김대성(Daeseung Kim),이상헌(Sangheon Lee) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The suspension systems of module unit are being evaluated to raise durability performance reliability on these days. Driving tests were carried out in the PG of KATECH after many sensors were attached in the vehicle. As driving tests result, wheel load, strain of suspension parts and car acceleration data were measured. The acquired data was used to make a driving signal of half road simulator by iteration process. Instead of wheel force transducer(WFT), only dummy wheel adapter has been installed to execute durability test generally. This results the inertia difference from the weight difference. Durability test was executed after additional dummy wheel adapter was installed to compensate this phenomenon. A comparison of strain history, frequency and local strain rate was made between the only dummy wheel adapter installation condition and additional dummy wheel adapter installation condition. As result, the mass effect of dummy wheel adapter was analyzed. And spring displacement and velocity were also analyzed to comprehend vertical behavior characteristic of suspension system on the only dummy wheel adapter installation condition over against additional dummy wheel adapter installation condition.