• 반도체디스플레이기술학회지
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• 제16권1호
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• pp.97-101
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• 2017

In this paper, IGZO thin film transistor (TFT) was fabricated with cross-linked Poly (4-vinylphenol) (PVP) gate dielectric for flexible, transparent display applications. The PVP is one of the candidates for low-temperature gate insulators. MIM structure was fabricated to measure the leakage current and evaluate the insulator properties according to the annealing temperature. Low leakage current ( <0.1nA/cm2 @ 1MV/cm ) was observed at $200^{\circ}C$ annealing condition and decreases much more as the annealing temperature increases. The electrical characteristics of IGZO TFT such as subthreshold swing, mobility and ON/OFF current ratio were also improved, which shows that the performance of IGZO TFTs with PVP can be enhanced by reducing the amount of incomplete crosslinking in PVP.

• Macromolecular Research
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• 제12권1호
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• pp.53-62
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• 2004

We have prepared polymer composites of low-density polyethylene (LDPE) and ionomers (Surlyn 8940) containing polar segments and metal ions by melt blending with carbon black (CB) as a conductive filler. The resistivity and positive temperature coefficient (PTC) of the ionomer/LDPE/CB composites were investigated with respect to the CB content. The ionomer content has an effect on the resistivity and percolation threshold of the polymer composites; the percolation curve exhibits a plateau at low CB content. The PTC intensity of the crosslinked ionomer/LDPE/CB composite decreased slightly at low ionomer content, and increased significantly above a critical concentration of the ionomer. Irradiation-induced crosslinking could increase the PTC intensity and decrease the NTC effect of the polymer composites. The minimum switching current (Ι$\sub$trip/) of the polymer composites decreased with temperature; the ratio of Ι$\sub$trip/ for the ionomer/LDPE/CB composite decreased to a greater extent than that of the LDPE/CB composite. The average temperature coefficient of resistance (${\alpha}$$\sub$T/) for the polymer composites increased in the low-temperature region.

• Macromolecular Research
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• 제12권1호
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• pp.112-118
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• 2004

With the goal of enhancing the creep resistance of ultra-high molecular weight polyethylene (UHMWPE), we performed gamma irradiation and post-irradiation annealing at a low temperature, and investigated the crystalline structures and mechanical properties of the samples. Electron spin resonance spectra reveal that most of the residual radicals are stabilized by annealing at 100$^{\circ}C$ for 72 h under vacuum. Both the melting temperature and crystallinity increase after increasing the dose and by post-irradiation annealing. When irradiated with the same dose, the quenched sample having a higher amorphous fraction exhibits a lower swell ratio than does the slow-cooled sample. The measured tensile properties correlate well to the crystalline structure of the irradiated and annealed samples. For enhancing creep resistance, high crystallinity appears to be more critical than a high degree of crosslinking.

• 폴리머
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• 제32권3호
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• pp.219-229
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• 2008

A pH sensitive ternary copolymer gel was synthesized in the presence of ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent through radical polymerization of vinyl acetate (VA), acrylic acid (AA) and methyl acrylate(MA) with a weight ratio of 1 : 1.3 : 1. A number of experiments were carried out to determine the swelling behavior of the gel under a variety of pH conditions of the swelling medium. As the pH of the swelling medium was changed from 1.0 to 8.0 at $37^{\circ}C$, the gel showed a shift in the pH-dependent swelling behavior from Fickian (n=0.3447) to non-Fickian (n=0.9125). The resulting swelling parameters were analyzed using graphical and statistical methods. The results showed that the swelling of the gel was controlled by the pH of the medium, i.e. $n=n_o{\exp}(S_{C}pH)$, where n is the diffusion exponent, $n_o(=28.9645{\times}10^{-2})$ is the pre-exponential factor and $S_C$(=0.1417) is pH sensitivity coefficient. The swelling behavior of the gel was also examined in aliphatic alcohols. The results showed that the rate of swelling increased with increasing number of carbon atoms in the alcoholic molecular chain.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.479-490
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• 1996

To utilize collagen as an implantable biomateriall the mcct widely used bovine skin origin Type I collagen was investigated Pepsin treated, Type I atelocollagen was extracted and crosslinked by the ultraviolet(W) ray with wavelength of 254nm or by various concentrations of glutaraldehyde to produce collagen membranes. The crosslink rates of the specimens were observed by a polarized light microscope, a scanning electron microscope, and a Fourier transform infrared (FT-lR) spectrometer. The followings are concluded 1. The collagen membranes produced by both 2.5% glutaraldehyde solution and 254nm UV ray irra- diation demonstrated similar morphologies on polarized light microscopic and scanning electron microscopic views. 2. The chemical structures of the crosslinked membranes by glutaraldehyde over 2.5% in concentrations revealed similar intensities to that of the UV ray irradiated one in FT-lR investigation. 3. To obtain optimal croulink in bovine stalin origin Type I atelocollagen, 2.5% glutaraldehyde solution or UV ray irradiation with 254nm wavelength is acceptable.

• Macromolecular Research
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• 제16권3호
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• pp.218-223
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• 2008

In order to obtain crosslinked poly(butylene succinate) (PBS) foams with a closed-cell structure, a commercial-grade PBS was first modified in the melt using two different branching agents to increase the melt viscosity. The rheological properties of the branched and crosslinked PBS were examined by varying the amount of the branching agents. The complex viscosity of the crosslinked PBS increased with increasing amount of the branching agent. However, it decreased with increasing frequency. When 2 phr of the branching agent was added to PBS, the storage modulus (G') was higher than the loss modulus (G") throughout the entire frequency range, showing that the addition of a branching agent increases the melt viscosity and elasticity of PBS effectively. Closed-cell PBS foams were prepared by mixing the chemical blowing agent with the crosslinked PBS. The effect of the foaming conditions such as temperature and time, and the amount of the crosslinking agent on the structure of the expanded PBS foams were also investigated.

• Elastomers and Composites
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• 제36권4호
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• pp.268-277
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• 2001

PPG, PEG, trimethylolpropane(TMP) 등의 폴리올에 MDI(4,4'-diphenyl methane diisocyanate)를 각각 혼합하고 경화시켜 여러가지 물성을 측정하였다. 경화시간은 PEG와 TMP의 함량이 늘어날수록 짧게 나타났고 분자량의 효과보다는 관능기의 수에 더 큰 영향을 받았다. NCO-OH 반응은 NCO-NCO반응보다 활성적이고 빠르게 일어났다. 경도는 가교밀도와 분자구조의 영향을 받았으며 NCO-NCO 반응으로 생긴 도막은 취약하였고 NCO-OH간의 반응으로 생긴 도막은 유연하였다. 부착력은 결정화도와 수축율이 클수록 낮은 값을 나타내었으며 TMP 함량이 증량될수록 높은 값을 나타내었다. 난연성은 난연제의 종류와 함량에 영향을 받았으며 난연효과는 IXOL B-251이 가장 우수하였고 TCCP는 수지와의 상용성이 좋지 않아 부분적으로 분리되었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.11.2-11.2
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• 2011

Polymer based organic photovoltaics have attracted a great deal of attention due to the potential cost-effectiveness of light-weight and flexible solar cells. However, most BHJ polymer solar cells are not thermally stable as subsequent exposure to heat drives further development of the morphology towards a state of macrophase separation in the micrometer scale. Here we would like to show three different approaches for developing new electroactive polymers to improve the thermal stability of the BHJ solar cells, which is a critical problem for the commercialization of these solar cells. For one of the examples, we report a new series of functionalized polythiophene (PT-x) copolymers for use in solution processed organic photovoltaics (OPVs). PT-x copolymers were synthesized from two different monomers, where the ratio of the monomers was carefully controlled to achieve a UV photo-crosslinkable layer while leaving the ${\pi}-{\pi}$ stacking feature of conjugated polymers unchanged. The crosslinking stabilizes PT-x/PCBM blend morphology preventing the macro phase separation between two components, which lead to OPVs with remarkably enhanced thermal stability. The drastic improvement in thermal stabilities is further characterized by microscopy as well as grazing incidence X-ray scattering (GIXS). In the second part of talk, we will discuss the use of block copolymers as active materials for WOLEDs in which phosphorescent emitter isolation can be achieved. We have exploited the use of triarylamine (TPA) oxadiazole (OXA) diblock copolymers (TPA-b-OXA), which have been used as host materials due to their high triplet energy and charge-transport properties enabling a balance of holes and electrons. Organization of phosphorescent domains in TPA-b-OXA block copolymers is demonstrated to yield dual emission for white electroluminescence. Our approach minimizes energy transfer between two colored species by site isolation through morphology control, allowing higher loading concentration of red emitters with improved device performance. Furthermore, by varying the molecular weight of TPA-b-OXA and the ratio of blue to red emitters, we have investigated the effect of domain spacing on the electroluminescence spectrum and device performance.

• 폴리머
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• 제25권3호
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• pp.311-317
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• 2001

본 연구에서는 반응성이 큰 친수성 단량체인 glycidylmethacrylate (GMA)를 이용하여 현탁중합법으로 bead type의 GMA-DVB 공중합체를 제조하고, 이들 공중합체를 trimethyl-ammonium chloride로 아민화하여 trimethylammonium기를 갖는 거대망상형 음이온 교환수지를 합성하였다. 여기서 지하수에 공존하는 음이온 중 $NO_3^-$ 제거에 가장 방해가 되는 $SO_4^{2-}$ 이 입체적으로 크다는 것에 착안하여 가교제인 divinylbenzene (DVB)의 양을 변화시켜 가교도에 따른 음이온에 대한 선택능을 확인하였고, 각각의 수지에 대한 물성과 $NO_3^-$ 에 대한 흡착능을 고찰하였다. 또한 FT-IR을 통하여 공중합체의 합성여부를 확인하였고, 또한 아민화 수율, 이온교환 용량 및 팽윤율을 평가하여 가교도에 따른 영향을 조사하였다. 여기서 DVB의 함량이 4wt%일 때 아민화 수율은 384.3%, 이온교환용량은 3.25 meq/g, 팽윤율은 77.1%로 가장 최적으로 나타났다.

• 공업화학
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• 제28권1호
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• pp.57-63
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• 2017

본 연구에서는 다양한 NCO index에서 물 함량 변화가 자동차용 폴리우레탄 시트 폼 패드의 정적 안락감에 미치는 영향을 알아보았다. 정적 안락감에 영향을 미치는 요인을 파악하기 위해 UTM을 사용한 정하중 특성 시험을 통하여 히스테리시스 곡선을 나타냈으며, 이를 통해 25% 변형 시 경도와 65% 변형 시 경도, hysteresis loop area, hysteresis loss (%), 그리고 Sag factor를 구하였다. 동일한 NCO index에서 물 함량이 증가함에 따라 우레아 결합의 증가로 경도가 증가하고, 가교밀도가 증가하는 경향을 swelling ratio 측정으로 확인하였으며, 이에 따라 복원력은 감소하는 경향을 확인하였다. 또한 표면 경도의 증가로 인해 Sag factor가 감소하는 경향을 확인하였다. 동일한 물 함량에서 NCO index가 증가함에 따라 우레탄과 우레아 결합이 이소시아네이트와 추가 반응하여 가교도와 경도가 증가하고 이에 따라 복원력이 감소함을 확인하였다.