Isoprene and Rubber. XIX. The Molecular Size of Rubber and Balata

1930 ◽  
Vol 3 (3) ◽  
pp. 519-521 ◽  
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Molecular Weight ◽  
Organic Solvent ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Dilute Solution ◽  
Decomposition Products ◽  
Viscosity Measurements ◽  
Gutta Percha ◽  
Preceding Work

Abstract It was shown in the preceding work that a very dilute solution of balata in an organic solvent contains macromolecules in solution and not micelles. The same is true of rubber. On the basis of these findings it is possible to calculate the molecular weight of rubber and balata from viscosity measurements by means of the formula developed in a previous work: M=η8p/c. Km. The supposition is made that the molecules of rubber and balata have the form of threads and double threads, respectively. Also it is necessary to determine the constant KKm, and this may be calculated in the case of low molecular products, where the average molecular weight can be determined as well as the viscosity of the solutions. Such semi-colloidal decomposition products were obtained by heating rubber or gutta-percha in either tetralin or xylene. As shown by the following table the four samples thus obtained gave the constant: 0.3×10−3,5

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.

Isoprene and Rubber. Part 20. The Colloidal Nature of Rubber, Gutta-Percha, and Balata

1930 ◽  
Vol 3 (4) ◽  
pp. 586-595
Author(s):  
H. Staudinger
Keyword(s):  
Molecular Weight ◽  
Characteristic Viscosity ◽  
Specific Viscosity ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Viscosity Increase ◽  
Preceding Work ◽  
Rubber Part

Abstract I. The Molecular Weight of Rubber, Gutta-Percha, and Balata In the preceding work the molecular weight of rubber and balata was calculated on the basis of relations between specific viscosity ηsp and molecular weight which are shown by semi-colloidal decomposition products, on the assumption that this relation is also true for eucolloids. The value ηr−1 was taken as the specific viscosity, i. e., the characteristic viscosity increase of a substance of definite concentration and known solvent. The expression “specific viscosity” has already been used by J. Duclaux. In viscosity investigations of nitrocellulose solutions he represents this by a constant K which is calculated from the relations of the change of viscosity at various concentrations derived by Arrhenius: Based on these constants, nitrocelluloses show different average molecular weights for the increase in viscosity, that is, this constant K is greater with high molecular products than with low. In the following, this constant represents not the specific viscosity, but the viscosity-concentration constant Kc; the earlier constant Km which, on the basis of the formula: expressed the relation between the specific viscosity and the molecular weight, is called the viscosity-molecular weight constant.

scholarly journals Average molecular weight of surfactants in aerosols

2007 ◽  
Vol 7 (5) ◽  
pp. 13805-13838 ◽  
Author(s):  
M. T. Latif ◽  
P. Brimblecombe
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Atmospheric Aerosols ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Ozone Exposure ◽  
Before And After ◽  
Fine Mode ◽  
Active Substances

Abstract. Surfactants in atmospheric aerosols determined as methylene blue active substances (MBAS) and ethyl violet active substances (EVAS). The MBAS and EVAS concentrations can be correlated with surface tension as determined by pendant drop analysis. The effect of surface tension was more clearly indicated in fine mode aerosol extracts. The concentration of MBAS and EVAS was determined before and after ultrafiltration analysis using AMICON centrifuge tubes that define a 5000 Da (5 K Da) nominal molecular weight fraction. Overall, MBAS and to a greater extent EVAS predominates in fraction with molecular weight below 5 K Da. In case of aerosols collected in Malaysia the higher molecular fractions tended to be a more predominant. The MBAS and EVAS are correlated with yellow to brown colours in aerosol extracts. Further experiments showed possible sources of surfactants (e.g. petrol soot, diesel soot) in atmospheric aerosols to yield material having molecular size below 5 K Da except for humic acid. The concentration of surfactants from these sources increased after ozone exposure and for humic acids it also general included smaller molecular weight surfactants.

Chromatography of heparin on Sepharose–lysine: molecular size fractionation and its relevance to thrombin and antithrombin III binding

1979 ◽  
Vol 57 (10) ◽  
pp. 1183-1190 ◽  
Author(s):  
M. W. C. Hatton ◽  
L. R. Berry ◽  
H. Kaur ◽  
A. Koj ◽  
E. Regoeczi
Keyword(s):  
Molecular Weight ◽  
Antithrombin Iii ◽  
Binding Capacity ◽  
Anticoagulant Activity ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Lysine Content ◽  
Heparin Binding ◽  
Significant Difference ◽  
Lysine Residues

Batches of Sepharose–lysine, which varied in lysine content from 35 to 430 μmol/g of dry gel, were prepared by varying the quantity of CNBr in the activation reaction. The batches were tested for heparin binding by using a controlled chromatographic procedure. Sepharose–lysine, containing < 150 μmol of lysine/g, did not significantly bind heparin whereas conjugates with > 400 μmol/g retained the entire heparin load. For intermediate batches of Sepharose–lysine (150–400 μmol/g) the quantity of heparin bound largely paralleled the lysine content. Thus, Sepharose–lysine of an intermediate lysine content separated heparin into an unretained fraction and a bound fraction which was recovered from the column by eluting with 1 M NaCl. On testing for anticoagulant activity by factor Xa inhibition assay, no significant difference in specific anticoagulant activity was observed between these heparin fractions and the heparin load. However, from gel filtration studies, a substantial difference in molecular size was noted. An unretained heparin fraction from Sepharose–lysine was of a lower average molecular weight than the parent heparin. In contrast, a retained heparin peak was of a higher average molecular weight compared with the parent heparin. These observations were confirmed by studying the chromatographic properties of low (10 000) and high (23 000) molecular weight heparin samples on various Sepharose–lysine batches. A model is proposed to explain this discriminating property of Sepharose–lysine. For a conjugate containing 400 μmol/g, the mean lysine spacing is calculated at 47 Å (1 Å = 0.1 nm), which is approximately equivalent to five to six disaccharide units in heparin.The property of Sepharose–lysine to bind heparin was compared with the affinities of the mucopolysaccharide for both thrombin and antithrombin III. Evidence has been proposed for the involvement of lysine residues of antithrombin III in this process. Our investigations suggest that lysine, in addition to arginine, groups of thrombin are also involved in heparin binding. By specifically modifying two to four lysine residues using nitrous acid, the heparin-binding capacity of the enzyme and its plasma clotting activity were largely destroyed, although the esterase activity was retained.

THE FRACTIONAL PRECIPITATION OF GR-S: THE EFFECT OF CONCENTRATION OF THE SOLUTION ON THE EFFICIENCY OF FRACTIONATION

1953 ◽  
Vol 31 (9) ◽  
pp. 868-880
Author(s):  
L. H. Cragg ◽  
D. F. Switzer
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Conclusive Evidence ◽  
Careful Study ◽  
Dilute Solution ◽  
Fractional Precipitation

A careful study was made of the fractionation of GR-S (commercial poly(butadiene-co-styrene)) by stepwise precipitation, from solution in benzene, with the precipitant 50:50 (by volume) methanol-benzene. To determine the reproducibility of fractionation, particularly in the high-molecular-weight region, three runs were made with 2% solutions; and to determine the effect of concentration on efficiency, comparable fractionations were performed from solutions of three different concentrations—1, 2, and [Formula: see text] respectively. In each of the fractions the value of intrinsic viscosity, the viscosity slope constant β, and the viscosity-average molecular weight were determined. These provide conclusive evidence that in such a primary fractionation a much cleaner separation is accomplished from a dilute solution (1% or less).

Synthesis and Dilute-Solution Behavior of Model Star-Branched Polymers

1978 ◽  
Vol 51 (3) ◽  
pp. 406-436 ◽  
Author(s):  
B. J. Bauer ◽  
L. J. Fetters
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Melt Processing ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Dilute Solution ◽  
Long Chain

Abstract The occurrence of polymers branched in a random fashion is common. Chain transfer reactions can cause short- and long-chain branching in polymerizations such as the high-pressure polymerization of ethylene. Branching can also be introduced intentionally by the use of a polyfunctional monomer in end-linking polymerizations. Similar branching can be produced in addition polymerizations by the use of a small amount of difunctional monomer, e.g., divinylbenzene. There also has been much interest in graft polymerization by which long chain branches can be introduced onto a backbone, which is often a different polymer from the branches. The properties of branched polymers can be quite different from those of linear polymers of the same molecular weight. For example, bulk viscosities as well as concentrated and dilute solution viscosities can be lower for branched polymers than for a linear material of equivalent molecular weight. As an example, the melt processing behavior of polymers can be manipulated by alterations in the average molecular weight, molecular weight distribution, and the frequency and length of long branches in the molecules. Thus, there is an obvious need to correlate and characterize the type and degree of branching in a polymer with its effect on the physical properties in solution or melt. In all of the above examples of branching, there is a mixture of branched and unbranched material. The unbranched and branched polymers can have a wide molecular weight distribution, as can the branches themselves. Also, the frequency of branches and the segment lengths between branch points can vary. Hence, the physical properties of such materials represent an average of the properties of all the different species present.

Fractionation and Molecular Weight of Rubber and Gutta-Percha

1942 ◽  
Vol 15 (1) ◽  
pp. 1-16
Author(s):  
A. R. Kemp ◽  
H. Peters
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Average Molecular Weight ◽  
Latex Films ◽  
Molecular Weight Range ◽  
X Ray ◽  
Gutta Percha ◽  
Approximate Composition ◽  
Association Effect ◽  
Insoluble Portion

Abstract 1. Evaporated latex films and Bolivian fine para contain a chloroform-soluble fraction of about 62 per cent, whereas the soluble portion of crepe and smoked sheets is about 86 per cent. The average molecular weight of these sols, which contain the low polymers and “resin”, range from about 130,000 to 180,000, the more soluble type having the lower value. 2. Diffusion and precipitation methods were employed to fractionate R. C. M. A. crepe, and the following data indicate the approximate composition and molecular weight range of the soluble hydrocarbon fractions separated: 3. The chloroform-insoluble portion of crepe contains a nonlinear type of hydrocarbon, judged by x-ray and viscosity studies. These methods show that the chloroform-insoluble portion of ammonia-preserved latex films contain extremely high-molecular rubber hydrocarbon which is easily oriented to give the regular x-ray crystalline pattern for rubber. 4. Freshly tapped latex contains a large proportion of petroleum-ether-soluble fraction, which becomes insoluble in this solvent on standing in the presence of ammonia. Ammonia-preserved latex films are soluble in chloroform or in hexane containing alcohol-acetone or acetic acid; this insolubility is thus an association effect, which is overcome by the addition of a polar solvent. 5. Viscosity studies on fractions of balata and gutta-percha show that their hydrocarbons have an average molecular weight of about 42,000 and cover a narrow polymeric range.

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.

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