• Applied Biological Chemistry
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• 제38권2호
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• pp.147-150
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• 1995

에탄올처리 찰가자미껍질 젤라틴의 젤라틴농도, pH, 정치온도 및 시간과 같은 겔화조건에 대한 물리적 특성 및 색조의 변화를 측정하였다. 젤라틴의 농도가 증가할수록 겔강도, 녹는점과 같은 물리적 특성은 증가하였고, 일정농도에서의 이러한 값들은 에탄올처리한 젤라틴이 무처리한 젤라틴에 비하여 컸다. 젤라틴 졸의 pH가 에탄올처리한 젤라틴의 경우 6.0일 때, 무처리한 젤라틴의 경우 5.0일 때, 겔강도, 졸화온도 및 겔화온도가 가장 높았고, 이를 벗어난 $pH\;5.0{\sim}7.0$의 범위에서는 서서히 감소하였으며, pH 5.0이하 및 pH 9.0이상에서는 급격히 감소하였다. 젤라틴 졸을 겔화시키기 위하여 정치시키는 온도의 경우 낮을수록, 정치시키는 시간의 경우 길어질수록 겔강도 및 졸화온도는 높았다. 겔화조건을 동일하게 하였을 때 에탄올처리한 젤라틴이 무처리한 젤라틴보다 물리적 특성값이 높게 나타났다.

• 멤브레인
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• 제28권5호
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• pp.326-331
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• 2018

축전식 탈염(capacitive deionization)에 이용할 수 있는 폴리페닐렌 옥사이드(PPO) 음이온 교환막의 가교결합에 대해 조사하였다. 브롬화와 아민화 반응단계를 거쳐 PPO 음이온 교환 고분자를 제조하고 비스페놀 A 디글리시딜에테르(BADGE), m-페닐렌디아민(m-PDA), 헥사메틸렌디아민(HMDA) 등으로 가교하였다. 가교에 따른 겔화되는 시간은 HMDA > m-PDA > BADGE 순으로 짧았으며, 일정한 함량 이상으로 실온에서 가교하면 1-메틸피롤리돈(NMP)과 같은 비양성자성 용매(aprotic solvent)에 녹지 않아 내화학성이 증대되었다. 가교제(BADGE) 함량에 따른 음이온 교환막의 이온 교환 용량과 함수율을 측정하고 비교하였다. HMDA 용액에 침적하여 표면 가교한 PPO 음이온 교환막을 축전식 탈염에 적용한 결과 그 탈염 성능은 가교하지 않은 막과 비교하여 흡착단계의 초기 부분을 제외하고 거의 차이가 없었다.

• Tissue Engineering and Regenerative Medicine
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• 제15권6호
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• pp.761-769
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• 2018

BACKGROUND: Bioprinting has recently appeared as a powerful tool for building complex tissue and organ structures. However, the application of bioprinting to regenerative medicine has limitations, due to the restricted choices of bio-ink for cytocompatible cell encapsulation and the integrity of the fabricated structures. METHODS: In this study, we developed hybrid bio-inks based on acrylated hyaluronic acid (HA) for immobilizing bio-active peptides and tyramine-conjugated hyaluronic acids for fast gelation. RESULTS: Conventional acrylated HA-based hydrogels have a gelation time of more than 30 min, whereas hybrid bio-ink has been rapidly gelated within 200 s. Fibroblast cells cultured in this hybrid bio-ink up to 7 days showed >90% viability. As a guidance cue for stem cell differentiation, we immobilized four different bio-active peptides: BMP-7-derived peptides (BMP-7D) and osteopontin for osteogenesis, and substance-P (SP) and Ac-SDKP (SDKP) for angiogenesis. Mesenchymal stem cells cultured in these hybrid bio-inks showed the highest angiogenic and osteogenic activity cultured in bio-ink immobilized with a SP or BMP-7D peptide. This bio-ink was loaded in a three-dimensional (3D) bioprinting device showing reproducible printing features. CONCLUSION: We have developed bio-inks that combine biochemical and mechanical cues. Biochemical cues were able to regulate differentiation of cells, and mechanical cues enabled printing structuring. This multi-functional bio-ink can be used for complex tissue engineering and regenerative medicine.

• 한국세라믹학회지
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• 제39권2호
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• pp.113-119
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• 2002

The effect of ultrasonic radiation is reported for silica-poly(ethylene glycol) system prepared without the solvent using sol-gel processing by varying various parameters such as ultrasonic irradiation time, PEG content and HCl/TEOS molar ratio. The property of sonogel is compared with classic gel which has been prepared with ethanol as a solvent by traditional sol-gel processing. SEM, BET, DTA-TGA, density and Vickers hardness measurements are carried out for analyzing the samples. The gelation time is found strongly dependent on radiation time, PEG content and pH value, and has been discussed on the basis of existing theories. The $SiO_2-10$ & 20 wt% PEG sonogel exhibited superior optical, physical and gel properties as compared to the classic gel, hence, found suitable for device applications. The ultrasonic radiation increased the density and surface area, and also reduced the pore size which is well supported by the shift in the peak of DTA curve. The DTA thermogram was found similar to that of pure silica gel.

• 한국응용과학기술학회지
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• 제24권4호
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• pp.339-346
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• 2007

The influence of adding urea to phenol-formaldehyde (PF) resins as a co-polymer component were investigated aiming at synthesizing useful phenol-urea-formaldehyde resins. Urea was added at 10% by total resin weight. Several methods for the addition of urea to the PF resins during synthesizing resins to see the co-polymerization occurs between urea and PF resins. The urea was added at the beginning, at three different middle stages, and at the end of PF resin synthesis. The copolymerized methylene bridges between phenol and urea molecules were not observed by $^{13}C-NMR;$ no signal around 50ppm. The curing of urea-modified PF resins, evaluated by dynamic mechanical analysis(DMA), showed some differences among the resins. DMA gel times ranged from 2.75 min to 3.25 min and the resins made with earlier urea additions showed slightly shorter gel times. The longest cure time and gelation time was observed for the resin PFU. Catalyst effects on the DMA cure time values of resins were not significant with different amounts of catalyst or different types of catalyst for all resins tested. Gel times of urea-modified PF resins shortened the most by triacetin catalyst.

• 한국산림과학회지
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• 제77권3호
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• pp.294-302
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• 1988

본(本) 실험(實驗)은 낙엽송(落葉松)(Larix leptolepsis) 수피(樹皮)로부터 추출(抽出)한 수피추출물(樹皮抽出物)의 특성(特性)을 조사(調査)하고 그들 추출물(抽出物)의 접착제화(接着劑化)의 가능성(可能性)을 평가(評價)하기 위해 실행되었다. 수율(收率)과 반응도(反應度)의 측정(測定)을 통해 온도(溫度) 및 시간(時間)의 영향(影響)과 탄산화(炭酸化) 및 설폰화(化)의 효과(效果)를 조사하였다. 목재접착제(木材接着劑)로의 적용(適用) 가능성(可能性)을 구명하기 위해서는 33% 농도(濃度)에서 점도(粘度)와 겔화시간(化時間)을 측정(測定)하였다. 그 결과(結果)는 다음과 같다. 1. 수율(收率)과 반응도(反應度)가 모두 높은 $80^{\circ}C$에서 120분(分)의 추출(抽出)이 적정온도(適正溫度) 및 시간(時問)이었다. 2. 탄산화(炭酸化)는 1% $Na_2CO_3$에서 설폰화(化)는 1% $Na_2SO_3$ : $NaHSO_3$와 0.25% $Na_2SO_3$에서 가장 큰 효과(效果)를 얻었으며 이들중 0.25% $Na_2SO_3$에 의한 설폰화(化)가 수율(收率)과 반응도(反應度)를 가장 크게 증가시켰다. 3. 온수추출액(溫水抽出液)의 수율(收率)은 17.2%이며 1% NaOH와 5% NaOH 추출액(抽出液)의 수율(收率)은 각각(各各) 38.6%와 44.6%이었다. 4. 온수추출액(溫水抽出液)의 반응도(反應度)는 68.8%로 가장 높았으며 1% NaOH와 5% NaOH 추출액(抽出液)의반응도(反應度)는 각각(各各) 49.3%와 25.8%이었다. 5. 각(各) 추출액(抽出液)은 33% 농도(濃度)에서 점도변화(粘度變化)가 매우 심했다. 특히 1% NaOH 추출액(抽出液)은 점도(粘度)가 매우 높았으며 5% NaOH 추출액(抽出液)은 오히려 점도(粘度)가 낮았다. 6. 추출액(抽出液)의 겔화시간(化時間)은 pH 7-10에서 가장 낮은 값을 나타냈으며 pH 4에서 가장 높은 값을 나타냈다. 파라포름알데히드의 이용(利用)은 37% 포름알데히드보다 겔화시간(化時間)을 더 연장시켜 주었다. 7. 온수추출(溫水抽出)의 설폰화(化)와 1% NaOH 추출(抽出)의 설폰화(化)를 제외(除外)한 다른 추출방법(抽出方法)은 높은 점도(粘度)(1% NaOH 추출(抽出))와 비경화성(比硬化性)(5% NaOH 추출(抽出), 5% NaOH 추출(抽出)의 설폰화(化)) 때문에 부적합한 것으로 밝혀졌다. 8. 접착제로(接着劑)로의 이용(利用)이 적합한 것으로 나타난 추출액(抽出液) 중 온수추출(溫水抽出)과 온수추출(溫水抽出)의 설폰화(化)는 반응도(反應度)가 뛰어난 반면 1% NaOH 추출(抽出)의 설폰화(化)는 비율면(比率面)에서 유리(有利)한 것으로 나타났다.

• 한국세라믹학회지
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• 제31권5호
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• pp.499-504
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• 1994

PbTiO3 thin films were prepared by sol-gel spin coating method using metal alkoxide and diethanolamine (DEA). The precipitation of the PbTiO3 sol occurred at pH 7.3 with HNO3 addition, regardless of the amount of DEA. The gelation time of the PbTiO3 sol was reduced with increasing amount of HNO3 and/or water. When the PbTiO3 films prepared by 0.2 molar coating solution were annealed at $650^{\circ}C$ for 30 min, dense and single phase perovskite films were obtained. Dielectric constant and loss tangent of the film were 239 and 0.01 at 1 kHz, respectively.

• Korea-Australia Rheology Journal
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• 제20권4호
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• pp.213-220
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• 2008

The effects of temperature on the rheological properties of the solutions of poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) in dimethyl acetamide (DMAc) were investigated in terms of frequency and concentration. The effects of temperature on the intrinsic viscosity of the solutions were discussed. In dynamic rheological measurement, the concentrated solutions showed a little unexpected rheological response; as temperature was increased dynamic viscosity was increased and the solutions exhibited more noticeable Bingham body character over the temperature range, 30 to $70^{\circ}C$. In addition, the solution gave longer relaxation time, lower value of loss tangent and higher value of yield stress at higher temperature and at higher concentration. On the other hand, the dilute solutions revealed that intrinsic viscosity was decreased and its Huggins constant was increased with increasing temperature. These physical parameters suggested that the increase of viscosity with increasing temperature resulted from the localized gelation of PVDF-HFP due to reduced solubility to the solvent.

• 한국세라믹학회지
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• 제28권12호
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• pp.943-952
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• 1991

Lead zirconate titanate(PZT) powders and thin films were prepared from an alkoxide-based solution by sol-gel method. Gelation of synthesized complex solutions, pyrolysis and crystallization behaviors of the dried powder were studied in accordance with a water content and a catalyst. PZT thin films were formed by spin-casting method on silicon and platinum substrates, and characterized. Ester produced from the reactions was completely removed when drying of the gel was finished. Pyrolysis property of the dried PZT gels were changed in order water content, class of catalyst, and quantity of catalyst. Crystalline Pb phase was transiently formed near 250$^{\circ}C$. Basic catalyst is good additive for a formation of perovskite phase in the films, and acidic catalyst for a densified film structure. By the analysis of RBS, Pb element in the PZT films were diffused into silicon substrate, and the pores, may be produced due to local densification around some grains in the films, make an origin of fault in microstructure when holding time goes to be longer at 700$^{\circ}C$.

• International Journal of Industrial Entomology and Biomaterials
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• 제27권2호
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• pp.312-316
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• 2013

Caffeine is a thermogenic agent that can be used in weight loss products. In order to achieve a sustained release of caffeine, silk fibroin (SF) film was uses as carrier. It has been shown that the loading method of caffeine into SF film affected the uniform distribution of caffeine in the SF film. When caffeine was added directly into SF solution, gelation has been occurred immediately and prevented the uniform distribution of caffeine. On the other hand, caffeine was dissolved in methanol in order to load the caffeine in SF film and crystallize the SF film at the same time. However, due to the fast evaporation of methanol, caffeine was recrystallized on the surface of SF film rather than penetrating into the film. Finally, caffeine was loaded into pre-crystallized SF film and uniform distribution of caffeine could be achieved. There was an initial burst of caffeine during the first 15 min, but after that a sustained release was achieved.