scholarly journals Intrinsic Viscosity-molecular Weight Relationship of Poly (Hexanediol Adipate)

2019 ◽  
pp. 1-8
Author(s):  
Jiankun Li ◽  
Zegang Zong ◽  
Dehua Hou ◽  
Bojun Tu ◽  
Weilan Xue ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Group Analysis ◽  
Gel Permeation Chromatography ◽  
Molecular Weights ◽  
The One ◽  
Relationship Of ◽  
The Relationship ◽  
End Group

In this work, a series of poly(Hexanediol adipate)(PHA) samples (103＜Mn＜104) with narrow molecular weight distribution were prepared by the polymerization between adilic acid and 1,6-hexandiol. End-group analysis was applied to determine the number average molecular weight (Mn) of PHA. Gel permeation chromatography (GPC) was employed to obtain the average molecular weights (Mn, Mv, Mw).The intrinsic viscosity of the samples in the tetrahydrofuran (THF) solution was determined at 298 K by the dilution extrapolation method and the one-point method. The relationship between the intrinsic viscosity and the molecular weight for PHA was studied by the Mark-Houwink-Sakurada (MHS) equation, and the parameters of equation were determined.

scholarly journals Molecular Simulation of Hyperbranched Polyester

2009 ◽  
Vol 5 (1) ◽  
pp. 563-569
Author(s):  
Liu Yanmei ◽  
Li Haihua ◽  
Tai Yulei ◽  
Chao Guoku ◽  
Zhao Yajuan
Keyword(s):  
Molecular Weight ◽  
Simulation Model ◽  
Empirical Equation ◽  
Gel Permeation Chromatography ◽  
Acid Value ◽  
Hyperbranched Polyester ◽  
Molecular Weights ◽  
The Core ◽  
Relationship Of ◽  
The Relationship

A new types of hyperbranched polyester was synthesized by the 2,2-bis(hydroxymethyl) propionic acid as an AB2-type monomer and glycerol as the core moiety. Molecular weights were confirmed by Gel Permeation Chromatography. Acid values were titrated by KOH. The hydroxy value was obtained by titration. Furthermore, we calculate logarithmic value of acid value, hydroxy value, and molecular weight, respectively, and the simulation model curves were obtained. Based on the simulation model curves, we establish the empirical equation of the relationship of molecular weight, acid value and hydroxy value.

Physical Properties of Fractions of GR-S and Their Vulcanizates

1949 ◽  
Vol 22 (2) ◽  
pp. 494-517 ◽  
Author(s):  
John A. Yanko
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Large Scale ◽  
Average Molecular Weight ◽  
Three Dimensional ◽  
Reduced Pressure ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
Straight Line ◽  
The Relationship

Abstract A large-scale precise fractionation of GR-S (X-55) was carried out at 25° C, using a fractional precipitation technique. Nine fractions, each weighing approximately 150 grams and comprising about 11 per cent by weight of the original unfractionated sample, were obtained, with number-average molecular weights varying from 4000 to 1,650,000. High molecular fractions undergo gelation rapidly, even when dried in the absence of light at reduced pressure, and the higher the molecular weight of the fraction, the greater the amount of gel formed. Compared to unfractionated butadiene-styrene copolymers of similar gel contents, the gel portions of the higher molecular fractions had unusually high swelling indices, indicating qualitatively that the average molecular weights between points of effective cross-linking in the three-dimensional gel structure were higher than those found in the past in unfractionated samples of similar gel contents. Through the concentration range studied, the intrinsic viscosity values varied as a straight-line function of the concentration terms for all the fractions. However, the negative slopes of these lines increased as the molecular weight of the fraction increased, demonstrating the greater dependence of the intrinsic viscosity values of the higher molecular fractions on the concentration variable. The relationship between number-average molecular weight, as determined by osmometric measurements, and limiting intrinsic viscosity of the GR-S fractions is given by the equation: [η]0=5.4×10−4 M0.66, which is similar to that obtained by French and Ewart. The μi values calculated from the equation of Huggins were essentially the same (0.35) through the molecular range 12,400 to 723,000.

scholarly journals Study on Preparation of Water-Soluble Chitosan with Varying Molecular Weights and Its Antioxidant Activity

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Dang Xuan Du ◽  
Bui Xuan Vuong
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Dose Range ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Chitosan Solution ◽  
Water Soluble ◽  
Molecular Weights ◽  
Ph Level ◽  
The One

The preparation of water-soluble chitosan (WSC) with various molecular weights by gamma Co-60 irradiation of chitosan solution (5%) in the presence of hydrogen peroxide (1%) combined with acetylated reaction was carried out. The average molecular weight (Mw) of chitosan was measured by gel permeation chromatography (GPC). The chemical structure and the crystallinity of chitosan and WSC were characterized by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD), respectively. The antioxidant activity of WSC and chitosan was investigated using the free radical 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS•+). Obtained results showed that chitosan with Mw of 18–90 kDa could be efficiently prepared by this technique in the dose range from 10 to 24.5 kGy. After the acetylated process, the resulting WSC possesses good solubility in a wide pH level of 2–12, and WSC with low molecular weight exhibited significantly higher antioxidant activity than the one with high molecular weight. In detail, the antioxidant activity was 14.7%, 70.5%, 84.2%, 89.4%, and 97.5% for WSC samples prepared from chitosan with Mw of 140.2 kDa, 91.4 kDa, 51.2 kDa, 35.3 kDa, and 18.1 kDa, respectively, at the same reaction time of 90 min. Moreover, the antioxidant activity of WSC was higher than that of chitosan. Thus, WSC prepared by gamma Co-60 irradiation and acetylated process can be potentially applied as a natural antioxidant agent.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

TAPPI Journal ◽  
2021 ◽  
Vol 20 (6) ◽  
pp. 381-391
Author(s):  
JULIANA M. JARDIM ◽  
PETER W. HART ◽  
LUCIAN LUCIA ◽  
HASAN JAMEEL
Keyword(s):  
Molecular Weight ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Systematic Investigation ◽  
Kraft Pulping ◽  
Molecular Weights ◽  
Lignin Recovery ◽  
Lignin Reactivity ◽  
Kinetics Of

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

Molecular Weights and Intrinsic Viscosities of Polyisobutylenes

1943 ◽  
Vol 16 (3) ◽  
pp. 493-508
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Chain Structure ◽  
Molecular Weight Range ◽  
Molecular Weights ◽  
Satisfactory Precision ◽  
Heterogeneous Polymers ◽  
Definition Of

Abstract Experimental methods for fractionating polyisobutylene and for determining osmotic pressures have been described. The ratio π/c of osmotic pressure to concentration has been found in the case of cyclohexane solutions of polyisobutylene to vary nonlinearly with concentration, contrary to recent theories advanced by Huggins and the writer. The slope of this relationship appears to be independent of molecular weight. Reliable methods for extrapolating π/c to c=0 have been established, enabling the determination of absolute molecular weights with satisfactory precision up to values of about 1,000,000. Molecular weights of polyisobutylenes calculated from Staudinger's equation are too low; the discrepancy is more than ten-fold at high molecular weights. On the basis of data for carefully fractionated samples covering a two-hundred-fold molecular weight range, the intrinsic viscosity is found to be proportional to the 0.64 power of the molecular weight. This decided deviation from Staudinger's “law”cannot in this instance be attributed to nonlinear chain structure, as Staudinger has sought to do in other cases. This dependence of molecular weight on intrinsic viscosity leads to the definition of a “viscosity average”molecular weight which is obtained when the relationship is applied to heterogeneous polymers. The viscosity average is less than the weight average molecular weight, which would be obtained if Staudinger's equation were applicable, and greater than the number average obtained by osmotic or cryoscopic methods.

Influence of Thermal Treatment on the Molecular Weights of Polyhydroxyalkanoate Containing 3-Hydroxyhexanoate

2013 ◽  
Vol 812 ◽  
pp. 250-253 ◽  
Author(s):  
Yoga Sugama Salim ◽  
Chin Han Chan ◽  
Kumar Sudesh ◽  
Seng Neon Gan
Keyword(s):  
Molecular Weight ◽  
Thermal Treatment ◽  
Gel Permeation Chromatography ◽  
Polymer Processing ◽  
Polymer Chains ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Ftir Spectrometer ◽  
Major Reduction ◽  
End Group

With blooming interests in the research of biodegradable polyesters produced from microorganisms as well as polymer processing and technology, this study is intended to reveal the influence of thermal treatment on the molecular weight of poly (3-hydroxybutyrate-co-3 mol% 3-hydroxyhexanoate)/P(3HB-co-3 mol% 3HHx), a copolymer of polyhydroxyalkanoates (PHA). P(3HB-co-3 mol% 3HHx) was thermally treated using Differential Scanning Calorimeter and analyzed using Gel Permeation Chromatography and Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectrometer. Results from gel permeation chromatography suggest a major reduction of molecular weight up to 50 % when P(3HB-co-3 mol% 3HHx) is exposed to 180 °C for 30 mins. The half-time degradation of P(3HB-co-3 mol% 3HHx) treated at 170 °C and 180 °C is 14.1 and 9.9 mins, respectively. FTIR spectroscopy shows an increase absorbance intensity of P(3HB-co-3 mol% 3HHx) after thermal treatment, indicating a formation of more alkenyl and carboxylic end-group in polymer chains due to random chain scissions.

Article

1998 ◽  
Vol 76 (11) ◽  
pp. 1699-1706 ◽  
Author(s):  
Jonathan Z Knaul ◽  
Mohammad R Kasaai ◽  
V Tam Bui ◽  
Katherine AM Creber
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Solvent System ◽  
Similar Degree ◽  
Degree Of Deacetylation ◽  
Molecular Weights ◽  
Good Accord ◽  
Gel Permeation ◽  
Weight Analysis

Starting from a chitosan sample with a degree of deacetylation of 71%, three separate sample sets were generated by successive deacetylation and reacetylation processes. The degree of deacetylation of samples was determined by UV spectrometry supported by thermogravimetric analysis. The molecular weight of chitosan samples was determined in a solvent system of 0.25 M CH3COOH/0.25 M CH3COONa, using viscometry and gel permeation chromatography (GPC) with a TSK-gel column. The first set of samples had a similar degree of deacetylation (DDA) but differing molecular weights. The second set of samples had a similar molecular weight but differing degrees of deacetylation. The Mark-Houwink-Sakurada constants used for the determination of viscosity average molecular weight and the universal calibration of the GPC system were K = 1.40 × 10-4 dL/g and a = 0.83. Results showed that molecular weights determined from both techniques are in good accord only at lower degrees of deacetylation. This may be attributed to the fact that the chemical structure of chitosan samples could have been largely altered with increasing or decreasing degree of deacetylation. Nevertheless, the trend with which the molecular weights vary with the deacetylation time is consistent over a limited DDA range. A literature review of molecular weight analysis of chitosan is included.Key words: chitosan, degree of deacetylation, gel permeation chromatography, molecular weight, viscometry.

scholarly journals The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1543
Author(s):  
Juan Li ◽  
Zhaohua Liang ◽  
Chengtao Gao ◽  
Shanshan Luo ◽  
Shaowen Huang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Nucleating Agent ◽  
Organic Phosphate ◽  
Nucleating Agents ◽  
Tem Analysis ◽  
Molecular Weights ◽  
Dispersed Particles ◽  
Extrusion Method

Two kinds of organic phosphate nucleating agent (NA-11 and NA-21) were used in PP with different molecular weights through the melt extrusion method. The dispersibility of the nucleating agents in PP, and the effect of the nucleating agents on the molecular weight, rheological behavior and crystallization behavior of PP were investigated. SEM and TEM analysis showed that the average radius of the dispersed particles (nucleating agents) was larger in LPP than that in HPP. The good dispersion of NA-21 also created more nucleation embryos for the adsorption of polypropylene molecules than the agglomerated NA-11. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of HPP and LPP both decreased with the addition of a nucleating agent. The rotational rheometer and capillary rheometer analysis showed that the effect of NA-21 on reducing intermolecular entanglement was more significant, whether in HPP or LPP. The addition of NA-21 had less elastic energy storage and better flow stability, and could be processed at a higher speed. Simultaneously, the relaxation time in the blends with LPP was shorter than that with HPP. It was found that the crystallinity and nucleation efficiency of HPP/nucleating agent blends increased remarkably, while there was a barely perceptible increase in LPP/nucleating agent blends.

Influence Of High Molecular Weight Factor VIII On The Expression Of Factor VIII Procoagulant Activity

1981 ◽  
Author(s):  
W Muntean ◽  
W E Hathaway ◽  
R R Montgomery
Keyword(s):  
Molecular Weight ◽  
Factor Viii ◽  
High Molecular Weight ◽  
Procoagulant Activity ◽  
Two Stage ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
The One ◽  
Relationship Of ◽  
The Relationship

The relationship of the high molecular weight (HMW) moiety and low molecular weight (LMW) moiety of factor VIII in expressing procoagulant activity (VIII C) was studied. LMW VIII C was prepared by immunoadsorbent chromatography; HMW VIII was prepared by chromatographing hemophilic cryo- precipitate in 4% agarose. The LMW VIII C obtained by immunoadsorbent chromatography gave higher VIII C values when tested in the one stage partial thromboplastin time (PTT) system using von Willebrand’s disease plasma as substrate than using hemophilic plasma as substrate. This finding was shown to be due to the VIII related antigen (VIIIR:Ag) in the substrate plasmas. When the VIIIR:Ag was removed from the hemophilic substrate plasma by immuno-adsorption, the VIII C values obtained for the LMW VIII C were higher. Also, adding purified HMW VIII to the von Willebrand’s disease substrate plasma resulted in lower VIII C values for the LMW VIII C in the PTT system.When the LMW VIII C was tested in the two stage assay, all VIII C was adsorbed to A1(0H)3. The adsorption of the LMW VIII C was prevented by mixing it with hemophilic plasma. From normal undiluted plasma only 5-21% of VIII C and no VIII related antigen were adsorbed to A1(OH)3, but after activation of the factor VIII of normal plasma by small amounts of thrombin, most of the VIII C was adsorbed. No VIII related antigen was adsorbed after activation.Nevertheless, when unadsorbed LMW VIII C was assayed by the two stage method both with and without HMW VIII or VIIIR:Ag, the results were the same.Our studies suggest that VIIIR:Ag prevents to some extent the activation of LMW VIII C. LMW VIII C that is not bound or protected by VIIIRiAg is adsorbed from plasma by A1(0H)3. These findings may help explain the differences for VIII C found in some patients and certain clinical circumstances with the one and two stage assays.

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