• Polymer(Korea)
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• v.31 no.6
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• pp.532-537
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• 2007

The rheological properties of the solutions of atactic poly(vinyl alcohol)(PVA) in dimethyl sulfoxide (DMSO) were investigated in terms of molecular weight distribution (MWD) of the polymer. The dynamic viscosity (${\eta}#$) and loss modulus (G") for the PVA/DMSO solutions with broader MWD were lower than those with narrower MWD at the similar $M_w$. It could be explained by the fact that the free volume for the solution with broader MWD at the similar $M_w$ was increased. The storage modulus(G#) of 14 wt% PVA/DMSO solutions with broader MWD was higher than that with narrower MWD at a lower frequency than 1.3 rad/sec, but lower than that with narrower MWD at a higher frequency (>1.3 rad/sec). The slopes of modified Cole-Cole plots of the 14 wt% solutions showed that as the MWD was broadened, the phase transition with frequency was more noticeable.

• Polymer(Korea)
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• v.38 no.6
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• pp.735-743
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• 2014

The rheological measurement of polypropylene (PP) has been performed using a rheometer, an intrinsic viscometer, and an MI machine to predict the molecular weight and the molecular weight distribution. Also, GPC has been used for the determination of the molecular structure. The distribution broadness parameter using modified Carreau model has been used to make the correlation between the rheological parameter and the molecular structure instead of the rheological PI (polydispersity index) which is determined from the cross of modulus from the dynamic oscillatory measurement. Even though the rheological PI is useful to determine the molecular weight distribution of the PP using controlled rheology, which has narrow and uniform molecular weight distribution, but not suitable to determine the molecular weight distribution of the PP made from direct polymerization which has broad and various molecular weight distribution. However the distribution broadness parameter which determined from the index of the shear thinning of the PP melt well predicts the molecular weight distribution of PP.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.25 no.3
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• pp.1-21
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• 1999

화장품, 의료용, 가정용품 및 공업용제품에까지 광범위한 용도로 사용량이 많은 중요한 비이온 계면활성제의 종류 중에서 polyoxyethylene(POE) 부가형 계면활성제의 경우 그 부가몰수에 따라 특성이 달라지고 용도가 다르게 사용된다. 이때 부가된 분자들의 분자량이 크고 분포를 이루는 혼합물이기 때문에 분석이 매우 어렵다. 따라서 MALDI-TOF/MS 방법을 이용하여 이들의 분자량과 그 분포를 측정함으로써 쉽고 빠르게 측정할 수 있는 새로운 방법을 개발하고자 하였다. 이 논문에서는 화장품에 주로 사용되는 비이온 계면활성제를 선택하여 MALDI-TOF/AfS를 측정하여 스펙트럼으로부터 분자량 분포와 POE부가정도를 측정할 수 있었다. 그리고 이 조건을 적용하여 시중에 판매되는 제품에서 추출된 비이온 계면활성제의 MALDI-TOF/MS 스펙트럼으로부터 분자량 분포와 POE 부가 정도를 확인 할 수 있었다.

• The Korean Journal of Rheology
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• v.10 no.3
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• pp.137-142
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• 1998

유변물성 자료로부터 고분자의 다분산성을 예측하는 방법은 신속한 중합반응 공정 제어를 위해서 중요한 연구분야중 하나이다. 본 연구에서는 다양한 분자량과 분자량 분포를 가진 폴리에틸렌에 대한 Shroff와 macridis 가 제시한 다분산성 매개변수 ER과 ET를 구하 고 겔투과 크로마토그래피에서 얻은 Mw/Mn과의 상관관계를 조상하였다. Mw/Mn과 비례적 인 상관관계를 보여주었으나 ET는 상관성이 없는 것으로 나타났다. ER값에는 분자량 분포 도 외에 LCB의영향도 큰 것으로 나타났다. 또한 분자량 분포중에서 고분자량 부분의 미미 한 변화에도 ER이 크게 변해 GPC보다 다분산성의 변화를 더 민감하게 예측할수 있음을 알 수있었다.

• Korean journal of food and cookery science
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• v.18 no.2
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• pp.200-205
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• 2002

Corn starch was modified by the oxidation with sodium hypochlorite(NaOCl) and the changes in the distribution of molecular weight were examined. Corn starch was oxidized with 0.25, 0.5, 0.75, 1.0, and 1.5% active Cl/g of starch at pH 7.0 and 25$^{\circ}C$ for 10 min. Oxidation of corn starch caused a change in the molecular weight distribution of amylopectin. The fraction of highest molecular weight in native starch decreased gradually and the fraction of lower molecular weight increased with increasing oxidation. Also, λ$\sub$max/ and iodine binding capacities of oxidized starches decreased and the soluble carbohydrate content increased by oxidation. The differential scanning calorimetric results of oxidized starches showed that the temperature and enthalpies of gelatinization were not changed by oxidation; however, the more the starch was oxidized, the greater the extent of retrogradation.

• Journal of Animal Environmental Science
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• v.10 no.1
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• pp.29-36
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• 2004

These experiments were conducted to analyze the characteristics of organic compounds and molecular weight distribution according to the treatment steps of purifying system for pig wastewater. The results obtained are summarized as follow. 1. Raw pig wastewater contained 31 kinds of organic compounds such as acetic acid, 2-butanone, hexane, chloroform, propionic acid, butanoic acid etc. 2. After ozone treatment, 13 kinds of organic compounds such as ethene, pentane, 2-methylopropanal, hexane, furan and so on were detected in the wastewater. 3. After $TiO_2$ treatment, 12 kinds of organic compounds such as ethene, hexane, chloroform, 1-decene, silane and so on were detected from the effluent. 4. After both ozone and $TiO_2$ treatment, portion of molecular weight smaller than 500 Daltons and molecular weight between 500 to 1,000 Daltons in the wastewater increased.

• The Korean Journal of Rheology
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• v.1 no.1
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• pp.54-62
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• 1989

준희박과 농축용액에서 약간의 유연성을 갖는 강성막대형 고분자의 회전확산계수와 zero shear rate 점도를 예측하기 위해 한정된 강성 사슬모델이 제시되었다. 본 연구에서는 이제시된 모델을 분자량 분포를 갖는 다분산계로 확장시켰다. 분자들의 분자량 분포 (MW/Mn) 와 분포 함수를 알수 없기 때문에 해당분자에 가장 적당한 분자량 분포와 함수를 취하였다. 만약 이것들을 알고 있다면 제시된 모델로 회전확산계수와 zero shear rate 점도 등과 같은 인자들을예측할수 있었다. 단분산계의 경우와 같이 다분산계에서도 회전확산계수 의 평균분자 윤곽길이 의존도는 L-7 에 비례하는 것으로 나타났다. Doi와 Edwards 의 튜브 모델에 의한 L-9 과 다른 이유는 분자들의 거동을 관찰하기 위해 임의로 선정된 하나의 막 대형 고분자운동을 제약하는 정도가 심하지 않았으며 따라서 제약 완화시간도 훨씬 짧았기 때문이다. 더구나 점도와 회전 확산계수와 단분산계에서는 정성적으로 일치한데 제약 완화 시간도 훨씬 짧았기 때문이다. 더구나 점도와 회전적인 일치를 나타내었다. 이 모델로 기준 으로 하여 분자들의 길이와 종류에 관계없이 하나의 master curve를 그릴수 있었다.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.673-679
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• 2011

Bimodal high-density polyethylenes with different comonomer type and content were synthesized by polymerization of ethylene using Ziegler-Natta catalyst. Their structure and properties were studied using GPC, NMR, DSC and tensile test. It was found that ethylene/1-hexene copolymer exhibits higher tensile strength and elongation at break than that of ethylene/1-butylene copolymer with similar comonomer content. The molecular weight decreases as the comonomer content of the polymer increases. Short chain branching affects the crystallinity and thus the morphology and consequently the mechanical properties of the corresponding bimodal high-density polyethylenes. After SSA treated, the multiple endothermic peaks were observed. Multiple endothermic peaks are mainly attributed to the heterogeneity of ethylene sequence length and lamellar thickness. The difference of broadness index indicates that SCB distribution of polyethylene containing higher comonomer content has improved uniformity.

• Food Science and Preservation
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• v.11 no.4
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• pp.496-502
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• 2004

Purified acorn starch was obtained from alkali precipitation method. Acorn amylose and acorn amylopectin were fractionated from purified acorn starch by butanol improvement method. Gel permeation chromatography (GPC) was used to measure molecular weight distribution of acorn starch, acorn amylose, acorn amylopectin and corn starch, corn amylose, corn amylopectin. GPC measurement diagrams were obtained by each retention time. And then, we used DMSO and DMF as solvent, pullulan as standard material. We calculated the Number-average molar mass (Mn), Weight-average molar mass (Mw) and polydispersity from molecular weight distribution of each sample. As a result of estimating molecular weight using GPC, Mw of amylose has small value than Mw of amylopectin. From this fact, the molecular structural aspects of amylose and amylopectin were predicted and it was in good agrement with the tendency of polydispersity by GPC. The polydispersity of starch had big value than amylose and amylopectin, from this result, it might be known that the range of molecular weight appeared broad by heterogeneous properties of two components. The viscosity of purified acorn starch, amylose, amylopectin seperated from acorn starch, was decreased by increasing the shear rate and raising the temperature exponentially. Acorn starch solutions exhibited pseudoplastic power law fluid behavior.

• Journal of Plant Biology
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• v.35 no.3
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• pp.259-263
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• 1992

한국 마늘에 감염되어 있는 주된 바이러스 중의 하나로 알려진 마늘 잠복 바이러스 (GMV)의 분자 구조와 병 발생 메카니즘을 이해하기 위하여, 국부 감염 숙주 식물인 Vicia faba에 연속적으로 감염시킴으로써 마늘 잠복 바이러스를 정제하였고, GMV에 대한 전신 감염성 숙주 식물로 생각되는 leek에서 GLV를 대량으로 증식시켰다. 투과전자현미경을 이용하여 바이러스 입자를 관찰한 결과, 마늘 바이러스들의 입자의 길이는 200-2000 nm의 분포를 보였으나 입자의 대부분은 600-900 nm의 범위 안에 존재하였다. 반면 순수 분리된 GLV 입자는 평균 690 nm의 길이를 보여주었고, 유연한 실 모양이었다. SDS-PAGE 분석으로 혼합 감염된 마늘 잎으로부터 분리된 마늘 바이러스의 구조 단백질은 분자량 24,500-38,000 Da의 분포를 나타내었으나, GLV 껍질 단백질의 분자량은 34,000 Da으로 나타났다.