Determination of the Molecular Size and the Molecular Form of Natural Rubber by the Measurement of Light Scattering. I. Development of the Method and Orienting Measurements

1957 ◽  
Vol 30 (3) ◽  
pp. 805-822 ◽  
Author(s):  
G. V. Schulz ◽  
K. Altgelt ◽  
H. J. Cantow
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Natural Rubber ◽  
Molecular Form ◽  
Benzene Solution ◽  
Wave Length ◽  
Molecular Size ◽  
B Value ◽  
Optical Measurements ◽  
Thermodynamic Quantities

Abstract An experimental method of preparing and purifying natural rubber solutions in the absence of oxygen with an ultracentrifuge is presented. The solutions are suitable for optical measurements. Light scattering is measured as a function of concentration, angle, wave length and temperature. By determining molecular weight, diameter of the coiled molecule, and thermodynamic quantities (Δμ1, Δh1, Δs1) in this way it is possible to get information on branching of the rubber molecules. The method was used for cyclohexene solutions of a carefully tapped crepe rubber. The molecular weight was 1.3⋅106 and the end to end distance of the coil 1750 A˚. The heat of dilution was positive (endothermic) the B-value being nearly as high as that found in benzene solution by osmotic measurements. Comparing these results with measurements on unbranched polymethacrylate and polyisobutylene one can conclude that these rubber molecules are not or only slightly branched.

scholarly journals The molecular form of acetylcholinesterase as determined by irradiation inactivation (Short Communication)

1974 ◽  
Vol 137 (1) ◽  
pp. 123-125 ◽  
Author(s):  
S. R. Levinson ◽  
J. C. Ellory
Keyword(s):  
Molecular Weight ◽  
Short Communication ◽  
Molecular Form ◽  
Electric Organ ◽  
Molecular Size ◽  
Erythrocyte Ghosts ◽  
Multiple Forms ◽  
Electrophorus Electricus ◽  
Membrane Bound

The molecular size of acetylcholinesterase (EC 3.1.1.7) from the electric organ of Electrophorus electricus and erythrocyte ‘ghosts’ was estimated in both membrane-bound and purified preparations by irradiation inactivation. Results suggest that the form of the enzyme in the membrane is a monomer of molecular weight approx. 75000 and that multiple forms of the enzyme observed in solubilized preparations are aggregates of this monomer.

Isoprene and Rubber. Part 29. High Molecular Hydrorubbers

1932 ◽  
Vol 5 (2) ◽  
pp. 136-140
Author(s):  
H. Staudinger ◽  
W. Feisst
Keyword(s):  
Molecular Weight ◽  
Catalytic Reduction ◽  
Molecular Form ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Rubber Part ◽  
Derivatives Of ◽  
Suitable Process

Abstract The molecular concept in organic chemistry is based upon the fact that the molecules, whose existence is proved by vapor density determinations, enter into chemical reactions as the smallest particles. If now it is assumed that organic molecular colloids like rubber are dissolved in dilute solution in molecular form then it must be proved that in the chemical transposition of macromolecules as well no change in the size of the macromolecules occurs. In the case of hemicolloids, therefore for molecular colloids with an average molecular weight of 1000 to 10,000, this has been proved by the reduction of polyindenes, especially of polysterenes, to hydroproducts with the same average molecular weight, and also by the fact that cyclorubbers do not change their molecular weight upon autoöxidation. The molecular weights of hemi-colloidal hydrocarbons are therefore invariable. This is much more difficult to prove in the case of rubber, although there are many more ways in which unsaturated rubber can be transposed than the stable polysterenes, polyindenes, and poly cyclorubbers. In most of the reactions with rubber, as in its action with nitrosobenzene, oxidizing agents, hydrogen halides, and halogens, an extensive decomposition takes place as a result of the instability of the molecule, which is referred to in another work. Therefore derivatives of rubber are not formed, but derivatives of hemi-colloidal decomposition products. The catalytic reduction of rubber in the cold appears to be the most suitable process of making it react without changing its molecular size in order to prove that in a chemical transposition its molecular weight remains the same.

Solution Properties of Polybutadiene and trans-Polyisoprene Fractions

1963 ◽  
Vol 36 (2) ◽  
pp. 488-501
Author(s):  
W. Cooper ◽  
D. E. Eaves ◽  
G. Vaughan
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Benzene Solution ◽  
Second Virial Coefficient ◽  
Virial Coefficients ◽  
Γ Radiation ◽  
Branched Polymer ◽  
Butyl Lithium ◽  
Second Virial Coefficients ◽  
Molecular Weights

Abstract Linear polybutadienes, prepared with butyl lithium as catalyst, and polybutadienes branched by exposure to γ-radiation have been fractionated and the fractions examined by osmometry and light scattering. Turbidimetric second virial coefficients (A2τ) of mixed polymer fractions are virtually the same as those of the higher molecular weight components of the mixtures for most compositions. This is true both for mixtures of linear with linear and linear with branched polymer. The higher the molecular weight of the fraction, the greater the effect; the addition of 1 per cent microgel to a linear polymer reduced A2τ by a factor of three. The presence of microgel or high molecular weight branched polymer has been shown to be responsible for the very high molecular weights previously reported for polybutadienes from light scattering measurements. It is conveniently removed by shaking the solutions with calcium sulfate. Second virial coefficients obtained either by light scattering or osmometry are, within the limits of experimental error, uninfluenced by branching in the polymer. In general those factors which lead to increased branching also result in increased polydispersity, and it is the latter which results in the decrease in A2τ. The fall of the osmotic second virial coefficient (A2τ) with molecular weight is much smaller than would be calculated theoretically, and the fall in A2τ is greater than would be expected, notwithstanding the fact that for some of the fractions Mw/Mn<1.1. This indicates that A2τ is sensitive to the low molecular weight species present in the fractions, whereas the reverse must apply to A2τ. Natural or synthetic trans-polyisoprene showed analogous behavior to polybutadiene, although, owing to experimental difficulties, sharp branched fractions could not be obtained. The following viscosity-molecular weight relationships were obtained in benzene solution: [η]=1.45×10−4M0.76 for butyl lithium-catalyzed polybutadienes, and [η]=4.37×10−4M0.65 for natural and synthetic trans-polyisoprenes.

Refractive Index of Natural Rubber for Different Wave Lengths

1950 ◽  
Vol 23 (3) ◽  
pp. 661-669 ◽  
Author(s):  
L. A. Wood ◽  
L. W. Tilton
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Natural Rubber ◽  
Wave Length ◽  
Low Molecular Weight

Abstract The refractive index of natural rubber and its variation with temperature and wave length are those which would be predicted for a similar hydrocarbon of low molecular weight. A two-constant equation of the Cauchy or Sellmeier type is inadequate to express the relation between refractive index and wave length for rubber. For convenient reference the best values resulting from the present investigation are recapitulated in Table VI.

LIGHT-SCATTERING STUDIES ON ALUMINUM DISTEARATE

1958 ◽  
Vol 36 (11) ◽  
pp. 1584-1595 ◽  
Author(s):  
A. E. Leger ◽  
J. C. Hyde ◽  
H. Sheffer
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Intrinsic Viscosity ◽  
Benzene Solution ◽  
Unit Length ◽  
Random Coil ◽  
Linear Molecule ◽  
Radius Of Gyration ◽  
Average Unit ◽  
Scattering Study

A light-scattering study of aluminum distearate in dilute benzene solution suggests that it is a linear molecule of random coil shape. This is further substantiated by intrinsic viscosity – molecular weight data, the constancy of the ratio of the molecular weight to the square of the radius of gyration (Rg), the value of Φ in Flory's intrinsic viscosity – molecular weight relationship, and the close agreement between the theoretical and experimental results found for the unit length of the polymer chain. This average unit length has been calculated to be 4.46 Å.

Determination of the Molecular Weight of Rubber and Polystyrene by the Methods of Light Scattering and Osmometry

1950 ◽  
Vol 23 (1) ◽  
pp. 89-97
Author(s):  
B. Dogadkin ◽  
I. Soboleva ◽  
M. Arkhangel'skaya
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Natural Rubber ◽  
Satisfactory Agreement ◽  
Molecular Weights ◽  
Molecular Compounds

Abstract 1. Experiments on the determination of the molecular weights of natural rubber and other high-molecular compounds by the methods of light scattering and osmometry are reported. 2. An osmometer of new design, suitable for determining molecular weights, is described. 3. It is shown that the method of light scattering yields values for molecular weights which are in satisfactory agreement with those obtained by the method of osmometry.

The Comparative Determination of the Molecular Weight of Rubber by the Methods of Light-Scattering and Osmometry

1956 ◽  
Vol 29 (2) ◽  
pp. 477-484
Author(s):  
B. Dogadkin ◽  
I. Soboleva ◽  
M. Arkhangelskaya
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Natural Rubber ◽  
High Molecular Weight ◽  
Scattering Method ◽  
Comparative Determination

Abstract 1. An account is given of experiments to determine the molecular weight of natural rubber and other high molecular-weight compounds by light-scattering and osmometry. 2. A new design of osmometer for determining molecular weight is described. 3. It is shown that the light-scattering method gives molecular weight values which agree satisfactorily with those given by the osmotic method.

scholarly journals MOLECULAR SIZE AND CONFIGURATION OF CELLULOSE TRINITRATE IN SOLUTION

1958 ◽  
Vol 36 (6) ◽  
pp. 952-969 ◽  
Author(s):  
M. M. Huque ◽  
D. A. I. Goring ◽  
S. G. Mason
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Ethyl Acetate ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Molecular Weight Range ◽  
Scattering Measurements ◽  
The Relationship

Viscosity and light-scattering measurements were made on several fractions and two unfractionated samples of cellulose trinitrate. The samples were prepared from bleached ramie, unbleached ramie, and cotton linters. The solvents were acetone and ethyl acetate. Viscosity was measured in a multishear viscometer designed for the purpose. Light-scattering measurements were made in a Brice-Phoenix Light-scattering Photometer modified to accommodate a cell which could be ultracentrifuged.The range of molecular weight investigated was from 6.5 × 105 to 25.0 × 105 The relationship between the z-average mean-square radius of gyration, [Formula: see text] and the z-average molecular weight was approximately linear in both solvents. The ratio of [Formula: see text] (where [Formula: see text] is the value of [Formula: see text] in the unperturbed state) was found constant in acetone but to increase with [Formula: see text] in ethyl acetate. This indicated that, whereas in acetone random coil configuration was attained, a configurational transition occurred in ethyl acetate in the molecular weight range investigated.The value of the exponent a in the relationship between intrinsic viscosity and molecular weight was found to be lower than unity but approximately equal in both solvents.The significance of the experimental data is discussed.

Suppressive Effect of Dextran on Platelet Adhesiveness

1966 ◽  
Vol 16 (03/04) ◽  
pp. 384-394 ◽  
Author(s):  
S Cronberg ◽  
B Robertson ◽  
Inga Marie Nilsson ◽  
J.-E Niléhn
Keyword(s):  
Molecular Weight ◽  
Bleeding Time ◽  
Slight Modification ◽  
Molecular Size ◽  
Suppressive Effect ◽  
Factor Ix ◽  
Factor V ◽  
Platelet Adhesiveness ◽  
History Of ◽  
Mean Molecular Weight

Summary43 normal volunteers, 3 patients with thrombophlebitis, and 1 patient with a high platelet adhesiveness and a history of thrombophlebitis have received dextran and its action on the mechanism of haemostasis has been studied. Platelet adhesiveness has been investigated by a slight modification of Hellem’s methods for whole blood and plasma. Dextran with a mean molecular weight of 70,000 produced a markedly lowered platelet adhesiveness together with a moderate prolongation of the Ivy bleeding time. Factor VIII was decreased by about 50% and factor V, factor IX and fibrinogen were decreased slightly more than could be expected from haemodilution alone. No fibrinolysis occurred. Dextran of lower molecular size was less potent. The possible use of dextrans as a thrombosis prophylactic agent is discussed.

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