유변학적 물성을 이용한 폴리프로필렌의 분자량과 분자량 분포를 결정하는 방법

이영실(Young Sil Lee),윤관한(Kwan Han Yoon) 한국고분자학회 2014 폴리머 Vol.38 No.6

폴리프로필렌의 분자량 및 분자량 분포를 예측하기 위해 레오메터, 고유점도측정기 및 MI(melt index) 기기등을 이용하여 유변 물성을 측정하였고, 분자구조해석에는 GPC가 사용되었다. 기존에 사용되어온 동적진동측정을이용한 교차 모듈러스에서 결정된 유변학적 PI(다분산 지표)와 변형된 Carreau 모델을 이용하여 계산된 분포 폭 매개변수(distribution broadness parameter)를 분자량 분포와의 관계를 비교해보았다. 유변학적 PI의 경우 이론적 근거가 부족하고, 압출에 의해 재 생성된 폴리프로필렌 시료에 대해서는 분자량 분포와 잘 일치하지만 반응기에서 중합된 시료 즉, 분자량 분포가 넓거나 다른 경우 잘 일치하지 않는다는 보고가 지배적인데 비해 분포 폭 매개변수는폴리프로필렌의 전단담화의 정도를 직접적으로 측정하는 것으로 분자량 분포를 잘 예측할 수 있음을 알았다. 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 beenused for the determination of the molecular structure. The distribution broadness parameter using modified Carreau modelhas been used to make the correlation between the rheological parameter and the molecular structure instead of the rheologicalPI (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 usingcontrolled rheology, which has narrow and uniform molecular weight distribution, but not suitable to determine themolecular weight distribution of the PP made from direct polymerization which has broad and various molecular weightdistribution. However the distribution broadness parameter which determined from the index of the shear thinning of thePP melt well predicts the molecular weight distribution of PP.

Calculation of molecular weight distribution using extended Cole-Cole model and quadratic mixing rule

이정행,김상모,조광수 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.1

We suggest a numerical method to calculate molecular weight distribution from linear viscoelastic data. The calculation method consists of three components: (1) a viscoelastic model of a monodisperse polymer as a function of molecular weight; (2) the mixing rule connecting viscoelastic data of monodisperse and polydisperse polymers through molecular weight distribution; (3) an algorithm which calculates the molecular weight distribution from the chosen mixing rule. Since we cannot measure the relaxation modulus of all monodisperse samples, we need an accurate monodisperse model for any molecular weight. It is known that a dynamic test is more reliable than a relaxation test, while the mixing rule needs relaxation modulus. Hence, we should have a smart numerical method that can convert dynamic data to relaxation modulus with the minimum conversion error. If we use the numerical method, then we have to generate numerical data from the model. Then it takes quite a long time. On the other hand, if we have a monodisperse model with the analytical relaxation spectrum, then calculation time can be reduced dramatically. Since the conversion from relaxation modulus to dynamic modulus suffers from smaller errors than the reverse conversion because of ill-posedness of the interconversion, the analytical conversion can be implemented more quickly at an acceptable level of errors. This paper proposes a new method satisfying the requirements.

The Distribution of 14C-chitosan by Different Molecular Weight in Mice

Kim, Kwang-Yoon,Kim, Young-Ho,Kim, Hee-Kyung,Bom, Hee-Seung,Kim, Ji-Yeul,Roh, Young-Bok,Yoshikazu Nishimura 대한방사선 방어학회 1998 방사선방어학회지 Vol.23 No.2

키토산은 키틴의 탈아세틸화반응을 통해서 얻어진 유전적 동석이 없는 천연착화제로써 방사성동위원소 혹은 중금속 이온의 제거제 및 체내 흡수 억제제로 알려져 왔다. 본 연구에서는 분자량이 다른 C-14 chitosan을 정맥투여 한 후 C-14 chitosan 분자량별 마우스 체내 대사과정을 알아보고자 하였다. ICR계 웅성 마우스(8-10주령, 체중 30-35g)를 사용하였다. C-14 chitosan은 증류수로 희석한 다음, 꼬리정맥을 통해 정맥 투여하였다. C-14 chitosan 투여후 6시간, 1일, 3일, 7일째 마우스를 희생시켜 혈액, 간, 신장, 비장, 폐, 근육, 고환, 오줌을 채취하였으며, 각각의 β-방사능을 측정하여 상대농도를 구하였다. 대부분의 C-14 chitosan이 6시간째에 오줌을 통해 체외 배출되었고, 체내대사과정은 분자량이 서로 다름에도 불구하고 비슷하였다. 간, 신장, 비장등에서 높은 방사능을 나타내었다. 조직간의 상대농도는 6시간째에 증가하다가 서서히 감소함을 알 수 있었다. 결론적으로 정맥 투여한 키토산은 분자량에 상관없이 대부분 오줌을 통해 체외배출 되고, 체내 장기중의 대사과정은 비슷하게 나타났다. Chitosan is a nontoxic natural chealtor which was made by chitin, and reduced a contamination of radiostrontium in animals. In this experiment, A different molecular weight of C-14 chitosan was intravenously administered to mice, and then the distribution of C-14 chitosan in the body was observed. Male mice (8 to 10 weeks, body weight of 30 to 35g) of ICR strain were used. C-14 chitosan was diluted with saline and then given intravenously in mice. After the administration of C-14 chitosan, mice was sacrificed at the 6th hour, 1st, 3rd, 5th, and 7th day. Beta radioactivities in the blood, liver, kidney, liver, muscle, testis, and urine was measured using a liquid scintillation analyzer. Most of the C-14 chitosan was excreted through urine within 6 hours. Biodistribution of C-14 chitosan was similar despite the difference of molecular weight. Higher distributions of radioactivities were found in the liver, kidney, spleen. The relative concentration in tissue increased for the 6 hours and then decreased. In conclusion, most of C-14 chitosan was excreted through urine despite the difference of molecular weight and, low molecular weight of C-14 chitosan showed higher distribution than high molecular weight of C-14 chitosan in tissues.

Modeling of molecular weight distribution of propylene slurry phase polymerization on supported metallocene catalysts

Kai Huang,Ruijin Xie 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.1

A mathematical model of the molecular weight distribution (MWD) based on a particle growth modeland the kinetic scheme is developed to simulate the MWD of the slurry phase propylene polymerizationon a silica-supported metallocene catalyst by means of the equations of moments. The model is used topredict molecular weight distribution, including the number-average molecular weight, the weight-average molecular weight, and the polydispersity index. The results show that the mass transfer hasgreat influence on the polymerization reaction, and it can broaden the MWD especially; moreover, theMWD can be evaluated by simulation; the average molecular weight increases as pressure ortemperature, and MWD shifts to long chain lengths as the effective diffusion coefficient increasingthought the influence is not remarkable; furthermore, the MWD’s simulation results are calculated,which fit greatly with the experimental data.

Effect of Analytical Parameters of Gel Permeation Chromatography on Molecular Weight Measurements of Urea-Formaldehyde Resins¹

Bora Jeong,Byung-dae Park 한국목재공학회 2017 목재공학 Vol.45 No.4

As the molecular weight (MW) of urea-formaldehyde (UF) resins had a great impact on their properties, this work was conducted to study effect of analytical parameters of gel permeation chromatography (GPC) on the MW measurement of UF resins. GPC parameters such as flow rate, column, detector temperature, and sample injection temperature were selected to compare number-average molecular weight (Mn), weight-average molecular weight (Mw), molecular weight distribution (MWD) and polydispersity index (PDI) of two UF resins with different viscosities. As expected, UF resin with higher viscosity resulted in greater Mn and Mw than those of low viscosity UF resin. When the flow rate increased, both Mn and Mw of UF resins decreased and MWD became narrower. By contrast, both Mn and Mw increased and MWD became wide when the column, detector, and sample injection temperature increased. The column, detector, and sample injection temperature of 50℃ at a flow rate of 0.5 mℓ/min resulted in the highest MW and broadest MWD for the GPC analysis. These results suggest that the apparent molecular size or a hydrodynamic radius of UF resin molecules dissolved in the mobile phase affect to Mn, Mw and MWD.

Analysis of Low Molecular Weight Collagen by Gel Permeation Chromatography

( Hee-jin Yoo ),( Duck-hyun Kim ),( Su-jin Park ),( Kun Cho ) 한국질량분석학회 2021 Mass spectrometry letters Vol.12 No.3

Collagen, which accounts for one-third of human protein, is reduced due to human aging, and much attention is focused on making collagen into food to prevent such aging. Gel permeation chromatography with Reflective Index (RI) detection (GPC/RI) was chosen as the most suitable instrument to confirm molecular weight distribution, and we explored the use of this technique for analysis of collagen peptide molecular sizes and distributions. Data reliability was verified by matrix-assisted laser desorption/ionization coupled to time-of-flight (MALDI-TOF) mass spectrometric analysis. The data were considered meaningful for comparative analysis of molecular weight distribution patterns.

Scaling analysis on the linear viscoelasticity of cellulose 1-ethyl-3-methyl imidazolium acetate solutions

권미경,이정행,조광수,이성준,김현철,정상원,이세근 한국유변학회 2019 Korea-Australia rheology journal Vol.31 No.3

Many researches have studied the viscoelasticity of cellulose/ionic liquid solutions through the conventional scaling rules which assume the monodisperse polymer. However, they are not suitable for cellulose since natural polymers such as cellulose have molecular weight distribution. In this paper, dynamic rheological behaviors of 1-ethyl-3-methyl imidazolium acetate solutions dissolving three kinds of celluloses were measured in a large range of concentrations from the dilute regime to the entangled semidilute regime at 25°C. We compared the viscosity-fitting scaling (Chen et al., 2011) and the phenomenological scaling to replace the conventional scaling. Two scaling methods were applied to the linear viscoelasticity of the cellulose solutions with different molecular weights and molecular weight distributions. The results of each scaling were compared by the superposition of master curves obtained from each scaling. The effects of molecular weight distribution were observed by the dependence of the scaling factors on concentration and molecular weight of cellulose.

Effect of polymer molecular weight on the tumor targeting characteristics of self-assembled glycol chitosan nanoparticles

Park, Kyeongsoon,Kim, Jong-Ho,Nam, Yun Sik,Lee, Seulki,Nam, Hae Yun,Kim, Kwangmeyung,Park, Jae Hyung,Kim, In-San,Choi, Kuiwon,Kim, Sang Yoon,Kwon, Ick Chan Elsevier 2007 Journal of controlled release Vol.122 No.3

<P><B>Abstract</B></P><P>To improve the <I>in vivo</I> tumor targeting characteristics of polymeric nanoparticles, three glycol chitosan (GC-20?kDa, GC-100?kDa, and GC-250?kDa) derivatives with different molecular weights were modified with cholanic acid at the same molar ratio. The resulting amphiphilic glycol chitosan–cholanic acid conjugates self-assembled to form glycol chitosan nanoparticles (GC-20?kDa-NP, GC-100?kDa-NP, and GC-250?kDa-NP) under aqueous conditions. The physicochemical properties of all three glycol chitosan nanoparticles, including degree of substitution with cholanic acid, surface charge, particle size and <I>in vitro</I> stability, were similar regardless of molecular weight. <I>In vivo</I> tissue distribution, time-dependent excretion, and tumor accumulation of glycol chitosan nanoparticles labeled with the near-infrared (NIR) fluorophore, Cy5.5, were monitored in SCC7 tumor-bearing mice, using NIR fluorescence imaging systems. Glycol chitosan nanoparticles displayed prolonged blood circulation time, decreased time-dependent excretion from the body, and elevated tumor accumulation with increasing polymer molecular weight. The results collectively suggest that high molecular weight glycol chitosan nanoparticles remain for longer periods in the blood circulation, leading to increased accumulation at the tumor site. Accordingly, we propose that enhanced tumor targeting by high molecular weight glycol chitosan nanoparticles is related to better <I>in vivo</I> stability, based on a pharmacokinetic improvement in blood circulation time.</P>

Preparation of polyethylene with controlled bimodal molecular weight distribution using zirconium complexes

Lee, J.,Kim, Y. Korean Society of Industrial and Engineering Chemi 2012 Journal of industrial and engineering chemistry Vol.18 No.1

Four zirconium complexes containing fully deprotonated 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tert-pentylphenol were used as catalysts for the polymerization of ethylene. In the presence of methylalumoxane (MAO) as a cocatalyst, the precursors were highly active for polyethylene with bimodal or multimodal molecular weight distribution.

Preparation of polyethylene with controlled bimodal molecular weight distribution using zirconium complexes

Junseong Lee,김영조 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1

Four zirconium complexes containing fully deprotonated 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tertpentylphenol were used as catalysts for the polymerization of ethylene. In the presence of methylalumoxane (MAO) as a cocatalyst, the precursors were highly active for polyethylene with bimodal or multimodal molecular weight distribution.