• 폴리머
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• 제35권1호
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• pp.23-29
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• 2011

소수성 설리카를 안정제로 하는 현탁중합법으로 $75^{\circ}C$에서 합성한 고분자입자들을 모세관 레오미터를 이용하여 전단점도를 측정하였다. 전단점도는 중량평균분자량이 증가하면서 비뉴톤거동을 나타내였다. 스타렌(St)/부틸메타크릴레이트(BMA)의 구성비를 변화하며 합성한 공중합체 입자를 이용하여 $170^{\circ}C$ 및 $190^{\circ}C$에서 측정한 전단점도는 분자량, 온도 뿐만 아니라 구성비에 따라서도 변화하였다. St/BMA의 구성비가 7/3, 5/5 및 3/7의 공중합체 (co-PSB) 입자의 경우 유사한 분자량을 나타내었지만 BMA의 구성비가 증가하면서 전단점도는 소폭 감소하였다. BMA의 비가 3/7을 초과하며 높은 전단속도에서의 전단점도는 급격히 감소하였다. 이는 BMA 구성비의 증가에 따른 PBMA 사슬의 길이의 증가로 인한 유동성 향상에 기인하는 것으로 판단된다. 카본블랙을 함유하는 co-PSB 복합체 업자의 전단점도는 카본블랙의 증가에 따라 점진적으로 증가하였으나, 카본블랙의 농도 증가에 따른 전단점도의 증가는 분자량의 증가 효과에 비교하여 미약하였다.

• 한국식품영양과학회지
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• 제30권2호
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• pp.277-282
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• 2001

The effects of chitosans with two different molecular weights (150 and 37 kDa) on the clarification of persimmon vinegar were investigated. The coagulated solids increased with increasing chitosan concentrations. Chitosan treatment had no effect on pH and acidity. Turbidity, browning, contents of tannin and soluble solids decreased with increasing chitosan concentrations. An increase in chitosan concentration resulted in an increase in color L* value and a decrease in a* and b* values. Reduction in turbidity and tannin contents somewhat differed depending on the molecular weights of chitosan. In sensory evaluation, chitosan treatment did not affect color and flavor over all concentrations tested. However, astringent taste was noticeably strong by treatment with 500mg/L chitosan, resulting in low overall acceptability. Therefore, the most effective clarification of persimmon vinegar was achieved by treatment with 400mg/L chitosan, irrespective of molecular weight.

• Bulletin of the Korean Chemical Society
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• 제20권3호
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• pp.333-336
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• 1999

The polyaniline films with various insoluble parts are fabricated. The oxidation state (1-y) of these polyaniline is 0.53 and 0.54, respectively. To control the interchain and intrachain interaction of the polymer, the polyaniline films are stretched with appropriate ratio. The insoluble part of polyaniline synthesized at room temperature (low molecular weight) is 12%-76% and that of polyaniline synthesized at 0 'IC (intermediate molecular weight) is 65%-89%. The low molecular weight polyaniline films with various drawing ratios have amorphous structure. In the intermediate weight polyaniline films, the crystallinity of films increases with drawing ratio as well as insoluble part. The difference of the insoluble part affects electrical conductivity which is increased dramatically with draw ratio. In particular, the higher insoluble part caused greater increase in electrical conductivity.

• BMB Reports
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• 제35권2호
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• pp.220-227
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• 2002

Two aspartate aminoransferase (EC 2.6.1.1) isoenzymes (AAT-1 and AAT-2) from Lupinus albus L. cv Estoril were separated, purified, and characterized. The molecular weight, pI value, optimum pH, optimum temperature, and thermodynamic parameters for thermal inactivation of both isoenzymes were obtained. Studies of the kinetic mechanism, and the kinetics of product inhibition and high substrate concentration inhibition, were performed. The effect of some divalent ions and irreversible inhibitors on both AAT isoenzymes was also studied. Native PAGE showed a higher molecular weight for AAT-2 compared with AAT-1. AAT-1 appears to be more anionic than AAT-2, which was suggested by the anion exchange chromatography. SDS-PAGE showed a similar sub-unit molecular weight for both isoenzymes. The optimum pH (between 8,0 and 9.0) and temperature ($60-65^{\circ}C$) were similar for both isoenzymes. In the temperature range of $45-65^{\circ}C$, AAT-2 has higher thermostability than AAT-1. Both isoenzymes showed a high affinity for keto-acid substrates, as well as a higher affinity to aspartate than glutamate. Manganese ions induced an increase in both AAT isoenzymes activities, but no cooperative effect was detected. Among the inhibitors tested, hydroxylamine affected both isoenzymes activity by an irreversible inhibition mechanism.

• 한국미생물·생명공학회지
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• 제20권2호
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• pp.190-195
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• 1992

Polythylene glycol/dextran 수성 2단계에서 polyethylene glycol의분자량과 농도가 증가할수록 체적비는 증가하고 분배계수는 감소하였다. 또한 dextran의 분자량이 증가할 수록 체적비는 감소하고 분배계수는 증가하였다. 한편 dextran의 농도가 증가할수록 체적비와 분배계수는 감소하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.553-556
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• 2005

Pyrolysis of polyethylene was carried out in the stainless steel reactor of internal volume of $40cm^3$. Pyrolysis reactions were performed at temperature $390-450^{\circ}C$ and the pyrolysis product were collected separately as reaction products and gas products. The molecular weight distributions(MWDs) of each liquid product were determined by GC-SIMDIS. Molecular weight of each product were decreased wi th increase of react ion temperature and time.

• 한국염색가공학회지
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• 제29권4호
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• pp.223-230
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• 2017

Three super hydrophobic fluorescence dyes were selected to dye high molecular weight polyethylene fiber and their molar absorptivity, emission spectrum, and quantum yield were measured. From the results of color strength on the fiber, all the three dyes exhibited linear increase according to the dye concentration and Fluoro3 dye showed the highest color strength among them. Emission strength of the fluorescence dyes on the fiber was investigated according to the dye concentrations. The emission was increased with the increase of the dye concentration at relatively low dye concentration and then after showing the maximum emission strength the emission was decreased at higher dye concentrations. The highest emission was obtained in Fluoro2 dye. Color fastness to washing and rubbing was generally good enough, however, especially to light, only Fluoro3 dye exhibited rating 3 acceptable practically and Fluoro1 and 2 was ratings 1 which is unacceptable level.

• Macromolecular Research
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• 제13권5호
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• pp.391-396
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• 2005

The polymerization of methyl methacrylate (MMA) was carried out using CuBr/bidentate phosphorus ligand catalyst systems. MMA polymerization with CuBr/phosphine-phosphinidene (PP) exhibited high conversion ($\~80\%$) in 5 h at $90^{\circ}C$ along with a linear increase of ln($[M]_0/[M]$) versus time, indicating constant concentration of the propagating radicals during the polymerization. The molecular weight of the prepared PMMA tended to increase with conversion, suggesting the living polymerization characteristic of the system. On the other hand, a large difference between the measured and theoretical molecular weight and a broad molecular weight distribution were observed, implicating possible incomplete control over the polymerization. This may have been caused by the low deactivation rate constant ($\kappa_{deact}$) of the system. The low $\kappa_{deact}$, would result in irreversible generation of radicals instead of reversible activation/deactivation process of ATRP. Polymerizations performed at different ligand to CuBr ratios and different monomer to initiator ratios did not afford better control over the polymerization, suggesting that the controllability of CuBr/phosphorus ligand system for ATRP is inherently limited.

• 폴리머
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• 제37권3호
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• pp.362-372
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• 2013

새로운 방법에 의하여 제조된 셀룰로오스-NMMO pre-dope를 이용한 셀룰로오스 섬유 및 필름 제조를 위한 압출가공 시 열분해 및 기계적 분해에 따른 셀룰로오스의 분자량 및 알파 셀룰로오스 함량 변화에 대하여 고찰하였다. 고속분쇄에 의해 제조된 pre-dope를 압출기에 통과시켜 용액으로 제조할 때 가공온도, 셀룰로오스의 농도 및 체제시간에 따라 셀룰로오스의 분자량 및 알파 셀룰로오스 함량 변화가 다양하게 나타났다. 셀룰로오스의 분자량과 알파 셀룰로오스 함량은 셀룰로오스의 농도가 낮을수록 온도가 높을수록 감소하였다. 셀룰로오스 농도 15% 및 짧은 체제시간 영역에서 알파 셀룰로오스 함량은 높은 전단으로 인해 온도가 높을수록 가장 큰 변화를 보였다. 다양한 가공조건으로부터 알파 셀룰로오스 함량변화 거동은 분자량 변화와 다른 거동을 보였으며 셀룰로오스 용액 제조를 위한 압출가공조건이 중요 요인임을 알 수 있었다.

• KSBB Journal
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• 제13권1호
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• pp.96-100
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• 1998

두 개의 프로모터 (trc와 Pp)를 Alcaligenes eutrophus에서 유래된 PHA 오페론에 삽입하여 재조합 대장균에서 분자량이 큰 polyhydroxybutyrate (PHB)를 얻고자 하였다. 두 개의 프로모터는 hydroxybutyric CoA와 PHA 중합반응의 유전자 발현을 각각 독립적으로 제어하기 위해 설계된 것이다 새로운 합성오페론을 포함한 플라즈미드는 E. coli DH5 $\alpha$ 에 transformation 되어 PHB 생산에 이용되었다. 본 실험의 가설로서 PHA 합성오페론의 IPTG에 의한 유도가 없을 경우 낮은 pHA synthase의 활성이 고분자 중합반응의 개시제 농도를 줄여주어 결과적으로 높은 연결수의 고분자를 생성할 것이라는 모델을 세웠다. 실제로 IPTG의 공급이 없는 발효실험을 통해 평균분자량이 $2.5{\times}10^7$ 인 거대 고분자를 얻을 수 있었다. PHA 생합성에 관여는 효소의 활성 분석으로 3-hydroxybutyric CoA의 중합을 촉매하는 효소인 PHA synthase의 활성을 가지고 In vivo에서 분자량이 제어됨을 확인하였다.