• 제목/요약/키워드: Photo-induced birefringence

검색결과 7건 처리시간 0.029초

Effect of Molecular Aggregation on the Photo-Induced Anisotropy in Amorphous Polymethacrylate Bearing an Aminonitroazobenzene Moiety

  • 김범준;박수영;최동훈
    • Bulletin of the Korean Chemical Society
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    • 제22권3호
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    • pp.271-275
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    • 2001
  • We investigated H-type molecular aggregation in a simply spin-coated amorphous homopolymer film of polymethacrylate containing push-pull azobenzene moieties. It was found that the aggregate formation was strongly influenced by thermal treatment an d that the aggregate created in the polymer film could be easily disrupted by irradiation of a linearly polarized light. In the first writing cycle of aggregated polymer film, photo-induced birefringence showed a steep increase to the highest value followed by a gradual decrease to the certain asymptotic value under longer irradiation of a linearly polarized light. This unique behavior could be attributed to the cooperative motion and the disruption of the aggregated molecules under continuous irradiation of light.

정밀 광학 부품의 복굴절 측정 방법에 관한 연구 (A Study on The Birefringence Measurement in Precision Optical Product)

  • 민인기;고영배;권창오;윤경환
    • Design & Manufacturing
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    • 제6권1호
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    • pp.90-94
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    • 2012
  • Recently, injection molding process became more popular than ever to produce large quantities of high precision products. Extensive studies have been conducted for reducing the residual stresses and birefringence in injection-molded optical products. Flow-induced and thermally-induced stresses and birefringence have been found as two main sources during injection molding process. Generally, quantitative value of birefringence can be measured with polarizing microscope using the compensator. However, it is difficult to measure low order retardation with microscope, so developing a measurement system for low order optical path difference is in need. In the present paper, a system using Photo Elastic Modulator (PEM) is demonstrated to measure low phase retardation in injection-molded products.

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Photoisomerization and Photo-induced Optical Anisotropy of Polymethacrylate Containing Aminonitroazobenzene

  • Park, Dong-Hoon;Cho, Kang-Jin
    • Fibers and Polymers
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    • 제2권1호
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    • pp.123-130
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    • 2001
  • Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy. Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiationg of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal(LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

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Liquid Crystal Alignment on the Films of Polymethacrylate and Polyurethane Bearing an Aminotroazobenzene Chromophore

  • Park, Dong-Hoon;Kim, Jae-Hyung;Cho, Kang-Jin
    • Macromolecular Research
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    • 제8권4호
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    • pp.172-178
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    • 2000
  • We synthesized polymethacrylate and polyurethane bearing a photosensitive azobenzene chromophore. Photo-induced birefringence of the thin film was observed under a linearly polarized light(λ = 532 nm). Dynamic behaviors of birefringence in two polymers were investigated in terms of the rate constants of growth and decay. An induced dichroism was observed from polarized UV-VIS absorption spectroscopy. Layers of two photosensitive polymers were used for aligning liquid crystal (LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

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광정보저장용 아조벤젠 타입 고분자에서의 광유도 복굴절 (Photo-induced birefringence on azobenzene type polymer film for optical memory)

  • 여세연;이현기;황의중;오차환;송석호;김필수;한양규
    • 한국광학회:학술대회논문집
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    • 한국광학회 2002년도 하계학술발표회
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    • pp.132-133
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    • 2002
  • 아조벤젠 고분자는 가역적 광이성화 과정에 의한 광유도 복굴절을 일으키는 물질로 광정보저장용 및 광소자용 매질로서 많은 연구가 이루어져 왔다. 일반적으로 아조벤젠 고분자는 rod-like 형태의 안정한 trans 상과 banana-like 형태의 준 안정한 cis 상의 이성체가 존재하고 이 두 이성체는 광에 의해 여기 되어 서로 다른 이성체로의 이성화가 일어나는데, 특히 막대 모양의 trans 상의 분자가 여기 시키는 광의 편광 방향에 수직으로 정렬하면서 복굴절이 유도되며 cis 상의 분자는 복굴절의 유도와 무관하다고 알려져 있다. (중략)

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The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • 제17권12호
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

러빙한 유리 기판을 이용한 반응성 액정 배향 (Alignments of Reactive Mesogen Using Rubbed Glass Substrates)

  • 이몽룡;배진우;김안나;윤형석;송기국
    • 폴리머
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    • 제39권1호
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    • pp.174-179
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    • 2015
  • 고분자 배향막이 없는 순수 유리 기판을 이용하여 광반응성 액정의 배향을 유도하였다. 유리 기판을 러빙하여 액정 배향을 유도한 경우, 고분자 배향막을 사용하여 유도한 경우와 같이 액정을 러빙 방향과 평행하게 배향할 수 있는 것을 편광 FTIR, 편광현미경, 복굴절 측정 등의 실험을 통해서 알 수 있었다. 순수 유리 기판을 러빙하여 액정 배향을 유도하는 메커니즘은 러빙 과정에서 유리 표면에 묻어나온 고분자들이 러빙 방향으로 늘어서 분자간 상호작용을 통하여 액정 분자들의 배향을 유도하는 것이다.