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.

A Rapid Determination of the Average Molecular Weight of Rubber in Hevea Latex

1951 ◽  
Vol 24 (2) ◽  
pp. 457-461 ◽  
Author(s):  
W. J. van Essen
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Rapid Determination ◽  
Average Molecular Weight ◽  
Lower Molecular Weight ◽  
Molecular Weights

Abstract A method is described for determining viscometrically the molecular weight of rubber in freshly tapped latex. For this purpose the latex is dissolved in a toluene-pyridine mixture. From the intrinsic viscosity of this solution the molecular weight of the rubber can be determined by the Staudinger equation and a known viscosity constant. Molecular weights varying between 238,000 and 480,000 have been found, depending on the kind of clone. Rubber in fresh latex does not have a lower molecular weight than in old preserved latex.

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.

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.

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.

EBULLIOMETRY AND THE DETERMINATION OF THE MOLECULAR WEIGHTS OF POLYMERS: PART I. THE SMALL EBULLIOMETER

1959 ◽  
Vol 37 (9) ◽  
pp. 1508-1516 ◽  
Author(s):  
W. R. Blackmore
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Molecular Weights

An ebulliometer that has been in routine use for the determination of the number average molecular weight of polymers is described. The results obtained with two different series of polythenes (which were also measured elsewhere) are given. These results show this ebulliometer to be subject to experimental difficulties which limit it to number average molecular weights of perhaps 20,000 depending on the precision required.

scholarly journals THE DETERMINATION OF MOLECULAR WEIGHT

1955 ◽  
Vol 33 (5) ◽  
pp. 755-762 ◽  
Author(s):  
A. F. Sirianni ◽  
I. E. Puddington
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
Organic Compounds ◽  
Chemical Stability ◽  
Pressure Difference ◽  
Molecular Weight Range ◽  
Vapor Pressure Difference ◽  
Static Measurement ◽  
Molecular Weights

The molecular weights of organic compounds of known constitution have been determined with satisfactory accuracy, using milligram quantities of materials, by a static measurement of the vapor pressure difference between pure solvents and solutions of the compounds. The method may be used over a considerable temperature range. The suitability of solvents is governed by their chemical stability and vapor pressure. Results obtained using compounds in the molecular weight range of 600–1000 are reported.

FURTHER DEVELOPMENTS IN THE VISTEX METHOD FOR THE DETERMINATION OF THE INTRINSIC VISCOSITY OF HIGH POLYMERS

1949 ◽  
Vol 27b (7) ◽  
pp. 666-681 ◽  
Author(s):  
D. A. Henderson ◽  
N. R. Legge
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Solvent Mixture ◽  
Gel Point ◽  
Styrene Copolymers ◽  
A Value ◽  
Pure Solvent ◽  
Butadiene Styrene

The intrinsic "vistex" viscosities of several series of butadiene–styrene copolymers of varying conversion and average molecular weight, dissolved directly from the latex in the vistex solvent mixture (toluene–isopropanol, 80/20 by volume), have been investigated and compared with the intrinsic viscosities of the corresponding coagulated, dried polymers dissolved in toluene. The intrinsic viscosity in toluene, [η]T, is related to the intrinsic vistex viscosity, [η]V, in toluene–isopropanol by the equation:—[Formula: see text]Hence, viscosity average molecular weight may be calculated from vistex measurements.A further development of the method has shown that, once the latex is dissolved in the vistex solvent, the solution may be diluted, within certain denned limits, by the addition of pure solvent (toluene) to obtain the several levels of concentration of polymer required for the determination of intrinsic viscosity. It is then possible, by extrapolation to zero concentration of polymer, to obtain a value for the intrinsic viscosity that is equal to the conventional intrinsic viscosity of the polymer in pure solvent after coagulation and drying under very mild conditions. The viscosity characteristics of butadiene–styrene copolymers of varying conversion appear to be represented, at conversions below the gel point, by the equation,[Formula: see text]where β′ and n are constants of the order of 0.25 and 1 for solutions in toluene and 0.1 and 2.5 respectively for vistex solutions. Distinct changes in β and/or n have been found at conversions in the region of and beyond the gel point.

INFLUENCE OF METHANOL ON VISCOSITY AND LIGHT SCATTERING PROPERTIES OF DEXTRAN SOLUTIONS

1956 ◽  
Vol 34 (4) ◽  
pp. 445-450 ◽  
Author(s):  
W. Donald Graham ◽  
Odette Patry ◽  
E. Helen Jackman
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Intrinsic Viscosity ◽  
Marked Effect ◽  
Average Molecular Weight ◽  
Alcohol Concentration ◽  
Methanol Concentration ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Apparent Weight

Failure to consider the presence of up to 16% by volume of methanol in solutions of dextran fractions had a very marked effect on apparent intrinsic viscosity determinations (the term apparent signifies that measurements were made assuming that the solvent was water only). Unless methanol were removed or otherwise taken into account, high erroneous results were obtained. Apparent weight average molecular weights determined by light scattering were not significantly affected at these alcohol concentrations. The relations found over the range 0 to 16% methanol for dextran samples with weight average molecular weights of 265,000, 155,000, and 72,000 held for the latter sample up to 44% methanol. In the higher range of alcohol concentration the apparent weight average molecular weight was depressed. The true intrinsic viscosity of dextran solutions decreased as methanol concentration was increased.

Unperturbed Polymer Chain Dimensions from Intrinsic Viscosities Determined in Good Solvents

1973 ◽  
Vol 46 (2) ◽  
pp. 470-476
Author(s):  
C. J. Stacy ◽  
R. L. Arnett
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Polymer Chain ◽  
Molecular Weights ◽  
Made In

Abstract Experimental criteria are presented to determine the region of validity of the intrinsic viscosity-molecular weight relation proposed by Stockmayer and Fixman for use in good solvents. Use of these criteria in several good solvents yields the same value for unperturbed polymer dimensions as do measurements made at “θ” conditions. Intrinsic viscosity determinations conforming to these criteria, made in two good solvents, allow the determination of weight-average molecular weights of the polymer solute.

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