• Title/Summary/Keyword: Molecular weight

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Determination of Viscosity Average Molecular Weight from Number and Weight Average Molecular Weights

  • Park, Eun-Soo;Yoon, Jin-San
    • Macromolecular Research
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    • v.8 no.5
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    • pp.243-245
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    • 2000
  • can be determined from the number and weight average molecular weight. When the value of the exponent, a, appearing in the relation between the intrinsic viscosity and the viscosity average molecular weight, is in the range from 0.6 to 0.8, as is the case for the most polymers, the viscosity average molecular weight is much more close to the weight average molecular weight than to the number average molecular weight.

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High Level Production of Supra Molecular Weight Poly(3-Hydroxybutyrate) by Metabolically Engineered Escherichia coli

  • Park, Jong-il;Lee, Sang-Yup
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.9 no.3
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    • pp.196-200
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    • 2004
  • The supra molecular weight poly(〔R〕-3-hydroxybutyrate) (PH B), having a molecular weight greater than 2 million Da, has recently been found to possess improved mechanical properties compared with the normal molecular weight PHB, which has a molecular weight of less than 1 million Da. However, applications for this PHB have been hampered due to the difficulty of its production. Reported here, is the development of a new metabolically engineered Escherichia coli strain and its fermentation for high level production of supra molecular weight PHB. Recombinant E. coli strains, harboring plasm ids of different copy numbers containing the Alcaligenes latus PHB biosynthesis genes, were cultured and the molecular weights of the accumulated PHB were compared. When the recombinant E. coli XL1-Blue, harboring a medium-copy-number pJC2 containing the A. latus PHB biosynthesis genes, was cultivated by fed-batch culture at pH 6.0, supra molecular weight PHB could be produced at up to 89.8 g/L with a productivity of 2.07 g PHB/L-h. The molecular weight of PHB obtained under these conditions was as high as 22 MDa, exceeding by an order of magnitude the molecular weight of PHB typically produced in Ralstonia eutropha or recombinant E. coli.

A Comparative Coagulopathic Study for Treatment of Vasospasm by Using Low- and High-molecular Weight Hydroxyethyl Starches

  • Hwang, Sung-Ho;Won, Yu-Sam;Yu, Jang-Sun;Yang, Jae-Young;Choi, Chun-Sik
    • Journal of Korean Neurosurgical Society
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    • v.42 no.5
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    • pp.377-381
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    • 2007
  • Objective : High-molecular-weight hydroxyethyl starch (HES) compromises blood coagulation more than does low-molecular-weight HES. We compared the effects of low- and high-molecular-weight HES for the treatment of vasospasm and investigated the dose relationship with each other. Methods : Retrospectively, in a series of consecutive 102 patients with subarachnoid hemorrhage (SAH), 35 patients developed clinical symptoms of vasospasm of these fourteen patients were treated with low-molecular weight HES for volume expansion while the other 21 received high-molecular-weight HES as continuous intravenous infusion. Prothrombin time (PT), partial thromboplastin time (PIT), fibrinogen level, and platelet count were all measured prior to initiation, during treatment and after termination of therapy for symptomatic vasospasm. The total dose of HES ranged from 5 L to 14 L and median infusion duration was 10 days. Results : A more pronounced PTT prolongation was observed in high-molecular-weight HES group compared with low-molecular-weight HES group. No other coagulation parameters were altered. Dosage (=duration) shows a positive correlation with PTT. Clinically, significant bleeding episodes were noted in four patients who received high-molecular-weight HES. Conclusion : Coagulopathy was developed in direct proportion to molecular weight of starch and dosages. We propose the extreme caution in the administration of HES solution for the vasospasm treatment.

Changes of Silk Fibroin Molecular Weight by Plastein Reaction (Plastein反應에 의한 絹피브로인의 分子量變化)

  • 김동건;판부막;소사효
    • Journal of Sericultural and Entomological Science
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    • v.40 no.2
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    • pp.131-135
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    • 1998
  • Changes of silk fibroin molecular weight was studied by enzymatic proteolysis and reverse reaction of enzymatic proteolysis (plastein reaction) using chromatography, X-ray diffraction and thermal analysis methods. When the treatment of enzymatic proteolysis with $\alpha$-chymotripsin to silk fibroin solution, a precipitate of Fcp fractions was formed. And, this was dissolved in LiBr aqueous solution, the precipitate of PIFcp fractions was obtained again. Fcp and PIFcp fractions showed silk IIand silk Itype structure, respectively. Fcp fractions was about 6,900 in molecular weight, PIFcp fractions obtained by plastein reaction on the precipitate of Fcp fractions increased molecular weight to abort 15,000. The molecular weight of Fcp fractions was increased by plastein reaction, but Fcp fractions almost transited to silk I type crystal. The structure of silk I type of PIFcp fractions was steady identified by X-ray diffraction and thermal analysis. As molecular weight of Fcp fractions was gradually low, PIFcp fractions was become to macromolecule little by little.

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A Study on the Color Reproduction of Halftone Image by used Factor N and Process Ink Characteristics (Factor N와 잉크특성을 고려한 망점화상의 색재현예측에 관한 연구)

  • 김성근
    • Journal of the Korean Graphic Arts Communication Society
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    • v.12 no.1
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    • pp.13-27
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    • 1994
  • Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printablility of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular weight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

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The Effect of Changing Molecular Weight of Rosin Modified Phenol Resin on Physical Properties of Litho Printing Inks (Rosin변성 phenol수지의 분자량 변화에 따른 평판인쇄 잉크의 물성변화에 관한 연구)

  • SungBinKim
    • Journal of the Korean Graphic Arts Communication Society
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    • v.12 no.1
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    • pp.145-157
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    • 1994
  • Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printability of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular \veight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

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Determination of Molecular Weight and Molecular Weight Distribution of Polypropylene Using Rheological Properties (유변학적 물성을 이용한 폴리프로필렌의 분자량과 분자량 분포를 결정하는 방법)

  • Lee, Young Sil;Yoon, Kwan Han
    • 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.

The Effect of the Molecular Weight of Poly(ethylene glycol) on Diffusion through Cellulose (폴리에틸렌글리콜의 분자량에 따른 셀룰로스에서의 확산 거동)

  • 윤기종;우종형;서영삼
    • Textile Coloration and Finishing
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    • v.16 no.1
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    • pp.48-52
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    • 2004
  • Diffusion/penetration rates of finishing agents are not a major criterion in the design of low molecular weight finishing agents. However, in the case of polymeric finishing agents, high molecular weights result in large hydrodynamic volumes and diffusion/penetration of the finishing agent into the substrate may become a critical factor in the design of textile finishing agents. Thus the effect of the molecular weight of a model compound, polyethylene glycol, on its diffusion through a cellulose membrane or cotton fabric is studied. Diffusion experiments of polyethylene glycol of molecular weight 400, 1000, 2000, 4600, 8000, and 10000 through cellulose membrane or fabric was carried out in a glass U-tube diffusion apparatus and the half penetration times and the penetration coefficients were determined. Both the half penetration times and the penetration coefficients exhibited a significant change between molecular weight 2000 and 2500 as the molecular weight of polyethylene glycol increased, suggesting that there is a critical molecular weight above which diffusion/penetration becomes difficult. Based on this study on a model compound, it is suggested that polymeric textile finishing agents can be expected to exhibit similar behavior.

Effect of Low Molecular Weight Species on the Interfacial Tension of PC/SAN Blend (PC/SAN 블렌드의 계면장력에 미치는 저분자량 성분의 영향)

  • Yang, Dongjin;Son, Younggon
    • Polymer(Korea)
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    • v.39 no.3
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    • pp.388-393
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    • 2015
  • Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

Size Characterization of Sodium Hyaluronate by Field Programming Frit Inlet Asymmetrical Flow Field-Flow Fractionation/Multiangle Light Scattering

  • Kim, Hoon-joo;Lee, Hee-jeong;Moon, Myeong-Hee
    • Bulletin of the Korean Chemical Society
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    • v.27 no.3
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    • pp.413-418
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    • 2006
  • Sodium hyaluronate (NaHA), water soluble polymer having ultra-high molecular weight, is characterized by using on-line frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) and multiangle light scattering (MALS). This study demonstrates the capability of power programming FI-AFlFFF for the separation of NaHA and the applicability of FI-AFlFFF with MALS for the characterization of molecular weight distribution and their structural information. Since sample injection and relaxation in FI-AFlFFF are achieved by using hydrodynamic relaxation, separation of high molecular weight polymers can be achieved smoothly without halting the separation flow. Experiments are carried out with the two different NaHA products (a raw NaHA sample and a thermally degraded NaHA product) and molecular weight distribution and conformations in solution are determined. Influence of sample filtration on the change of molecular weight distribution is also discussed.