• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1405-1407
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• 2009

We prepared polystyrene-b-poly(2-vinyl pyridine) (PSb-P2VP) lamellar films which is hydrophobic block-hydrophilic polyelectrolyte block polymer have 57 kg/mol-b-57 kg/mol. The result of UV-visible absorption spectra supported that effect of poly(ethylene oxide) on the band gap tuning of PS-P2VP photonic gel like salt effect.

• Bulletin of the Korean Chemical Society
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• v.29 no.12
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• pp.2329-2330
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• 2008

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2847-2848
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• 2012

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.279-279
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• 2010

Smart gels have recently associated with photonic crystals to form photonic gels. Since these photonic gels are capable of reversibly converting the volume change of gels induced in response to external chemical or electric stimuli into characteristic optical signals, they have been considered not only as a good platform for label-free chemical or biological detection, actuators or optical switches but also as a good model system to investigate gel swelling behaviour. Recently, we reported block copolymer photonic gels self-assembled from polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) block copolymers, and demonstrated that selective swelling of lamellar structure allows extremely large tunability of the photonic stop band from UV region to IR region ($\lambda$ peak=350~1,600 nm). Herein we report block copolymer photonic gels which exhibit strong tunable optical hysteresis and their applications. As nonlinear responses in swelling of hydrogels were often observed, photonic gels exhibit optical hysteresis with change of external pH. We demonstrate such optical hysteresis can be precisely programmed by controlling ion-pairing affinity. We anticipate that photonic gels with carefully tunned optical hysteresis are applicable to optical memory devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.261-261
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• 2010

Photonic band gap (PBG) materials have been of great interest due to their potential applications in science and technology. Their applications can be further extended when PBG becomes tunable against various chemical and electrical stimuli. In recent, it was found that tunable photonic band gap materials can be achieved by incorporating stimuli-responsive smart gels into PBG materials. For example, the characteristic volume phase transition of gels in response to the various external stimuli including temperature, pH, ionic strength, solvent compositions and electric field were recently combined with the unique optical properties of photonic crystals to form unprecedented highly responsive optical components. Since these responsive photonic crystals are capable of reversibly converting chemical or electrical energy into characteristic optical signals, they have been considered as a good platform for label-free chemical or biological detection, actuators or optical switches as well as a model system for investigating gel swelling behavior. Herein, we report block copolymer photonic gels self-assembled from polystyrene-b-poly (2-vinyl pyridine) (PS-b-P2VP) block copolymers. In this talk, we are going to demonstrate that selective swelling of lamellar structure can be effectively utilized for fabricating PBG materials with extremely large tunability. Optical properties and their applications will be discussed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.131-131
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• 2003

The advent of photonic technologies in the field of communications and data transmission has been heavily increasing the demand in integrated optical (IO) circuits capable of accomplishing not only simple tasks like signal, but also more sophisticated functions like all-optical signal routing or active multiplexing/demultiplexing. In the last decade, sol-gel technology has been widely used to prepare optical materials. Sol-gel processes show many promises for the development of low-loss, high-performance glass integrated optical circuits. However, crack formation is likely to occur during heat treatment in thick gel films. In order to overcome the critical thickness limitation, the organic-modified silicate has been widely used. In this case coating matrices have been prepared from the organo-silanes of T structures, acidic catalyst and the as-prepared gel films have been heat-treated below 200$^{\circ}C$ to avoid the crack formation and the degradation of organic components. However, the films prepared in the acidic condition and the low heat temperature make the films contain high OH groups which is the major optical loss function. In this work, C$\sub$6/H$\sub$5/SiO$\sub$1.5/ films were prepared on silicon substrate by sol-gel method using base catalyst in a PTMS/NH$_4$OH/H$_2$O/C$_2$H$\sub$5/OH system. The sol showed spinable viscosity at 50 wt% of solid content, and neglectable viscosity change with time. The films were crack-free and transparent after curing at 450 $^{\circ}C$, and highly condensed to minimize OH content in C$\sub$6/H$\sub$5/SiO$\sub$1.5/ networks. The effects of heat treatment of the films are characterized on the critical thickness, the chemical composition and the refractive indices by means of SEM, FT-IR, TGA, prism coupler, respectively.

• Polymer Science and Technology
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• v.22 no.6
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• pp.545-552
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• 2011

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.132-132
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• 2003

Second-order nonlinear optical(NLO) materials have been extensively studied for applications in photonic devices, such as frequency doubling and electro-optical(EO) modulation, because of their large optical nonlinearity, excellent processibility, low dielectric constant, and high laser damage thresholds. The poling behaviour of NLO chromophore in organic/inorganic matrixes showed the randomization of poled NLO chromophore in the absence of poling Held. The liquid crystal molecules in a droplet showed a long-range orientational order along a director. Therefore, liquid crystal effects on poling behaviour of NLO chromophore dispersed in organically modified inorganic sol-gel materials were investigated. Using sol-gel process for the development of NLO material has received increasing attention, Organically modifked inorganic NLO sol-Eel materials are obtained via incorporation of the organic NLO active chromophore into an alkoxysilane based inorganic network. One of the most important thing in this works was that tetraethoxysilane(TEOS) and methyltrimathoxysilane(HTMS) were used as precursor followed by hydrolysis and condensation without using any acidic catalyst during the process. The NLO chromophores in the liquid crystal nanodomains were well mixed with I/O hybrid matrix, deposited on transparent ITO-coated glasses. The poling behaviour of liquid crystal effects of NLO chromophore dispersed in I/O hybrid matrix were investigated by UV-vis spectroscopy. Size distribution and morphology of the NLO chromophores doped in the liquid crystal nanodomains dispersed in I/O hybrid matrix were investigated by SEM.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.402-406
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• 2009

$TiO_2$ thin films were surface-modified with atmospheric plasma and their photocatalytic activities were evaluated. The films were deposited on glass plates by dip-coating in a $TiO_2$ sol-gel solution and sintered at various temperatures for various times. Nitrogen plasma was used for the modification and the experiments were carried out varying operational parameters such as discharge power and treatment time. Photocatalytic activity was evaluated based on the degradation efficiency of methylene blue (MB) under irradiation of UV-A and fluorescent light. According to XPS analysis, a little amount of nitrogen was found to be doped in the film surface after the modification. As a result, photocatalytic activity increased under irradiation of UV-A and fluorescent light, especially fluorescent light.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1128-1134
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• 2010

Nanocarbon supported Fe/$TiO_2$ composite catalysts were prepared using CNTs (carbon nanotubes) and $C_{60}$ (fullerene) as nanocarbon sources by a modified sol-gel method. The Fe/$TiO_2$-nanocarbon composites were characterized by the BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and UV-vis spectra. In comparison with non-nanocarbon doped Fe/$TiO_2$ composites, the nanocarbon supported Fe/$TiO_2$ composites had higher absorption ability with a larger specific surface area, and showed higher photocatalytic activity during the degradation of methylene blue (MB) under visible light. The reasons for the obvious increase of photocatalytic activity indicated that the photoactivity not only benefits from nanocarbon introduced, but also relates to the cooperative effect of the Fe as a dopant.