scholarly journals Elucidation of the Relationship between Intrinsic Viscosity and Molecular Weight of Cellulose Dissolved in Tetra-N-Butyl Ammonium Hydroxide/Dimethyl Sulfoxide

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1605 ◽  
Author(s):  
Bu ◽  
Hu ◽  
Yang ◽  
Yang ◽  
Wei ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Dimethyl Sulfoxide ◽  
Intrinsic Viscosity ◽  
Molecular Level ◽  
Ammonium Hydroxide ◽  
Degree Of Polymerization ◽  
Regenerated Cellulose ◽  
Natural Cellulose ◽  
The Relationship

The determination of molecular weight of natural cellulose remains a challenge nowadays, due to the difficulty in dissolving cellulose. In this work, tetra-n-butylammonium hydroxide (TBAH) and dimethyl sulfoxide (DMSO) aqueous solution (THDS) were used to dissolve cellulose in a few minutes under room temperature into true molecular solutions. That is to say, the cellulose was dissolved in the solution in molecular level, and the viscosity of the solution is linearly dependent on the concentration of cellulose. The relationship between the molecular weight of cellulose and the intrinsic viscosity tested in such dilute solutions has been established in the form of the Mark–Houwink equation, η=0.24×DP1.21. The value of 1.21 indicates that the cellulose molecules dissolve in THDS quite well. The cellulose dispersion in the THDS was proved to be in molecular level by atomic force microscope (AFM) and dynamic light scattering (DLS). The reliability of the established Mark–Houwink equation was cross-checked by the gel permeation chromatography (GPC) and traditional copper (II) ethylenediamine (CED) method. No considerate degradation was observed by comparing the intrinsic viscosity and the degree of polymerization (DP) values of the original with and the regenerated cellulose samples. The natural cellulose can be molecularly dispersed in the multiple-component solvent (THDS), and kept stable for a certain period. A time efficient and reliable method has been supplied for determination of the degree of polymerization and the molecular weight of cellulose.

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.

scholarly journals The molecular-weight-dependence of the anti-coagulant activity of heparin

1978 ◽  
Vol 175 (2) ◽  
pp. 691-701 ◽  
Author(s):  
T C Laurent ◽  
A Tengblad ◽  
L Thunberg ◽  
M Höök ◽  
U Lindahl
Keyword(s):  
Molecular Weight ◽  
Binding Sites ◽  
Random Distribution ◽  
Degree Of Polymerization ◽  
Molecular Weight Range ◽  
High Affinity ◽  
Predicted Probability ◽  
Coagulant Activity ◽  
The Relationship ◽  
Molecular Weight Fractions

It is proposed that the anti-coagulant activity of heparin is related to the probability of finding, in a random distribution of different disaccharides, a dodecasaccharide with the sequence required for binding to antithrombin. It is shown that this probability is a function of the degree of polymerization of heparin. The hypothesis has been been tested with a series of narrow-molecular-weight-range fractions ranging from 5,600 to 36,000. The fractions having mol.wts. below 18,000 (comprising 85% of the original preparation) followed the predicted probability relationship as expressed by the proportion of molecules capable of binding to antithrombin. The probability that any randomly chosen dodecasaccharide sequence in heparin should bind to antithrombin was calculated to 0.022. The fraction with mol.wt. 36,000 contained proteoglycan link-region fragments, which may explain the deviation of the high-molecular-weight fractions from the hypothetical relationship. The relationship between anti-coagulant activity and molecular weight cannot be explained solely on the basis of availability of binding sites for antithrombin. The activity of high-affinity heparin (i.e. molecules containing high-affinity binding sites for antithrombin), determined either by a whole-blood clotting procedure or by thrombin inactivation in the presence of antithrombin, thus remained dependent on molecular weight. Possible explanations of this finding are discussed. One explanation could be a requirement for binding of thrombin to the heparin chain adjacent to antithrombin.

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.

Reaction of dimethyl sulfoxide with chlorothiolformates, hydrogen chloride, hydrogen fluoride, and hexafluoroisopropanol

1978 ◽  
Vol 56 (22) ◽  
pp. 2884-2888 ◽  
Author(s):  
Alan Queen ◽  
Alberta E. Lemire ◽  
Alexander F. Janzen ◽  
Michael N. Paddon-Row
Keyword(s):  
Molecular Weight ◽  
Dimethyl Sulfoxide ◽  
Hydrogen Chloride ◽  
Hydrogen Fluoride ◽  
Elemental Analysis ◽  
Molecular Weight Determination ◽  
Tert Butyl ◽  
Low Concentrations ◽  
Chloride Adduct

Dimethyl sulfoxide reacts with phenyl chlorothiolformate according to the stoichiometry:[Formula: see text]p-Chlorophenyl and tert-butyl chlorothiolformate appeared to react in a similar manner. The 1:1 hydrogen chloride adduct Me2SO:HCl was characterized by elemental analysis and proton and carbon nmr. A cryoscopic molecular weight determination of the adduct Me2SO:HOCH(CF3)2 showed it to be monomeric at low concentrations but associated at higher concentrations, suggesting a monomer–dimer equilibrium. The 1:2 adduct Me2SO:2HF is formed by the addition of anhydrous HF to dimethyl sulfoxide.

Basicity, Water Solubility and Intrinsic Viscosity of Carboxymethyl Chitosan as a Biofunctional Material

2012 ◽  
Vol 531 ◽  
pp. 507-510 ◽  
Author(s):  
Xiang Ping Kong ◽  
Juan Wang ◽  
Chun Jie Wang ◽  
Xia Wu
Keyword(s):  
Molecular Weight ◽  
Acetic Acid ◽  
Intrinsic Viscosity ◽  
Water Solubility ◽  
Average Molecular Weight ◽  
Carboxymethyl Chitosan ◽  
Molecular Weight Determination ◽  
Solution Ph ◽  
Alkaline Conditions

The basicity, water solubility, intrinsic viscosity and molecular weight of carboxymethyl chitosan (CM-chitosan) were investigated. The solution pH remained at about 9.2 at the concentration of higher than 2.0 g/L. The isoelectric point of CM-chitosan was about 4.5 of pH, and the solubility of CM-chitosan at the solution pH of 2.0 to 6.0 was lower than 5 g/L. The acetic acid could be replaced by hydrochloric acid as solvent for the viscosity-average molecular weight determination of chitosan. The intrinsic viscosity values of CM-chitosan have significant differences in acidic and alkaline conditions. The viscosity-average molecular weight of CM-chitosan was (3.8 ± 0.2) × 105, consistent with that of product chitosan of blank test.

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