Molecular Weight and Chain-Length of Natural and Synthetic Rubber

1934 ◽  
Vol 7 (1) ◽  
pp. 34-39 ◽  
Author(s):  
A. J. Wildschut
Keyword(s):  
Chain Length ◽  
Freezing Point ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Synthetic Rubber ◽  
The Subject ◽  
Molecular Substances ◽  
Very High

Abstract The determination of the chain-length of high molecular substances, as, e.g., rubber and gutta-percha, has lately been the subject of many investigations, though as yet the problem has not been definitely solved. The ordinary methods—measurements of the raising of the boiling point and of the depression of the freezing point—can be used only for molecular weights of some thousands, and there always remains a large gap between these compounds and the far greater natural ones. To bridge over this gap Staudinger has developed a supposition according to which it is possible to determine very high molecular weights by means of a viscosimetric method. This method depends on the known fact that for dilute solutions, in which the molecules do not hinder each other (so-called sol-solutions), the specific viscosity is proportional to the length of the molecule. For homologs we have:

Isoprene and Rubber. Part 44. Viscosity Measurements of Squalene and Hydrosqualene Solutions

1936 ◽  
Vol 9 (4) ◽  
pp. 573-578
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Physical Properties ◽  
General Relation ◽  
Basic Structure ◽  
Degree Of Polymerization ◽  
Specific Viscosity ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Rubber Part

Abstract The physical properties of highly polymerized substances, which are composed of fiber molecules, depend on the lengths of the chains of these fiber molecules. Thus tensile strength, elasticity, tendency to swell in solvents, and above all viscosity, are dependent on the length of chain of the particular substance. Among the substances, the properties of which vary thus, are rubber, gutta-percha, and balata. Since the length of fiber molecules can vary within wide limits, such physical properties as those mentioned above show wide variations in the case of rubber, gutta-percha, and balata. This is evident for example by a comparison of the properties of unmasticated rubber, which consists of long fiber molecules of a degree of polymerization of 2000, with the properties of masticated rubber, the greatly dissociated molecules of which have a degree of polymerization of only 500. The determination of the length of the fiber molecules is therefore of great importance in the case of highly polymerized substances. It has already been proved in past experiments with members of a series of homologous polymers, i. e., of substances the macromolecules of which have the same basic structure and differ only in length, that the molecular weights can be determined from viscosity measurements. This determination is based on the fact that there is a general relation between the specific viscosity and the length of the dissolved molecules, which can be expressed by the formula:

Computer determination of thoracic gas volume using plethysmographic "thoracic flow"

1980 ◽  
Vol 48 (5) ◽  
pp. 911-916 ◽  
Author(s):  
H. Lorino ◽  
A. Harf ◽  
G. Atlan ◽  
Y. Brault ◽  
A. M. Lorino ◽  
...  
Keyword(s):  
Regression Line ◽  
Time Derivative ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Computer Determination ◽  
The Subject ◽  
The Mean ◽  
Gas Volume ◽  
Very High

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume.

Isoprene and Rubber. Part 45. Viscosity Measurements of Solutions of Rubber and Hydrorubber in Various Solvents

1936 ◽  
Vol 9 (4) ◽  
pp. 579-584
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Carbon Tetrachloride ◽  
Chain Length ◽  
Homologous Series ◽  
Chlorinated Solvents ◽  
Cellulose Derivatives ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Rubber Part ◽  
Viscous Solutions ◽  
Chain Lengths

Abstract It has been observed many times that solutions of the same concentration of rubber in various solvents show marked differences in viscosity. For example, solutions of rubber in chlorinated solvents such as carbon tetrachloride have higher viscosities than do solutions of the same concentration in benzene or benzine. These differences in viscosity are attributable to the fact that the rubber molecules are solvated in different ways in the various solvents. It may be further assumed that in a particular homologous series of polymers, all members, i. e., substances of both high and low molecular weights, are solvated in the same solvent in the same way, for only in this way is it possible to believe that the specific viscosity of solutions of like concentration increases with increase in the chain length, as has been found to be true of cellulose derivatives. In the previous experiments with squalene and hydrosqualene (cf. preceding article), the constants necessary for calculating molecular weights and chain member indices n were determined. The constants for carbon tetrachloride are higher than those for benzene. In the case of squalene, therefore, as in the case of rubber, carbon tetrachloride gives more viscous solutions than does benzene. If, now, rubbers and hydrorubbers are solvated in the same way as squalene and hydrosqualene, then the same chain lengths of an homologous series of rubber polymers would be obtained by calculations using constants derived from the simple compounds of the chain member index, and from this the degrees of polymerization, are calculated by means of these constants in the formula:

scholarly journals II. On the lowering of the freezing-point of water by pres­sure

1880 ◽  
Vol 30 (200-205) ◽  
pp. 533-538 ◽  
Keyword(s):  
Thermal Effects ◽  
High Pressures ◽  
Freezing Point ◽  
Pressure Gauge ◽  
Quantitative Character ◽  
Gutta Percha ◽  
Iron Copper ◽  
William Thomson ◽  
Theoretical Discovery ◽  
Very High

The Cailletet pump may be conveniently employed to observe the thermal effects of compression on solid and fluid substances. Before engaging in an investigation on this subject, it was necessary to test the apparatus, and especially the manometer. For this purpose it seemed, on theoretical grounds, that observations on the lowering of the freezing-point of water by pressure would be a severe test of the accuracy of the pressure gauge, and the constancy of the records of the thermo-junctions under pressure. I am not aware of any quantitative experiments on this subject having been made under high pressures. Sir William Thomson carried the proof of the accuracy of Professor James Thomson’s great theoretical discovery to a pressure of 17 atmospheres. The experiments of Mousson (“ Pogg. Annalen,” 1858) were not of a quantitative character, being merely intended to show that ice at a temperature of —18° C. might still be liquefied by the application of an enormous pressure. The following experiments appear to show that a convenient manometer for very high pressures, based on the observation of the freezing-point, may be easily constructed. In all the following experiments the galvanometer, moving to the negative side, represents a cooling effect on the junction inside the bottle. One division on the arbitrary scale represented about of a degree C. Two thermo-junctions, made of iron-copper wires, insulated by a covering of marine glue, the junctions themselves being covered with a thin layer of gutta-percha dissolved in benzol, were employed in the experiments.

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 V. Gold-aluminium alloys

1900 ◽  
Vol 194 (252-261) ◽  
pp. 201-232 ◽  
Keyword(s):  
Aluminium Alloys ◽  
Freezing Point ◽  
Chemical Compounds ◽  
Chemical Society ◽  
Rapid Analysis ◽  
Chemical Combination ◽  
Point Curve ◽  
The Subject ◽  
The One

This paper is a study of the binary alloys composed of gold and aluminium. The fact that metals in many cases form definite chemical compounds with each other, is becoming increasingly evident as attention is given to the subject. But there are many pairs of metals whose freezing point-curve affords no indication of chemical combination, and which probably do not combine with each other under the conditions of our experiments. It is therefore desirable, in seeking for such compounds, to select a pair of metals which are known to have a peculiar relation to each other. We chose gold and aluminium for several reasons. First, on account of the beautiful purple compound of Sir W. Roberts-Austen, and on account of our own experiments (‘Journal Chemical Society/ vol. 74, 1894), which showed it to be a very stable body in solution. There was also the important point that the alloys of gold and aluminium admit of fairly rapid analysis by the determination of the gold. In the present paper the freezing point method is combined with a microscopic study of the alloys, and we hope that it will be found that the interpretation of the results is more conclusive than in previous papers of our own and of others in which only the one method or the other was employed.

Determination of the Molecular Weights and the Structures of Rubber, Gutta-Percha and Balata. Communication No. 258 on Macromolecular Compounds. Communication No. 49 on Isoprene and Rubber

1942 ◽  
Vol 15 (3) ◽  
pp. 473-522
Author(s):  
H. Staudinger ◽  
Kl Fischer
Keyword(s):  
Small Molecules ◽  
Colloidal Particles ◽  
High Viscosity ◽  
Molecular State ◽  
Colloidal Solutions ◽  
Great Tendency ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Long Time

Abstract The method used to determine the constitutions of rubber, gutta-percha and balata is essentially the same as that used for organic substances of low molecular weights, i.e., the substance is dissolved in a solvent, and the size and character of the particles in solution are determined. For a long time the nature of colloidal solutions of these hydrocarbons was in dispute. Up to twenty years ago, it was commonly assumed that the molecules of these hydrocarbons are relatively small, and that their colloidal particles are formed by the assemblage of small molecules into micelles through the agency of secondary forces. It seemed to Pummerer, Nielsen and Gündel that in certain solvents, such as camphor and menthol, rubber is dissolved in a low-molecular state. Subsequently, however, this observation was proved to be incorrect. According to the opinion of Meyer and Mark, colloidal particles of rubber are composed of relatively long primary-valence chains, which contain from 75–150 isoprene residues. These chains are, in turn, assembled into micelles by “micellar forces.” The authors explain this in the following way: “The high viscosity of rubber solutions, e.g., in benzene, would lead one to conclude that very large, highly solvated micelles are present in these solvents.” At the time, this hypothesis seemed to explain quite satisfactorily the nature of rubber and its solutions, for the great tendency of these solutions to undergo certain changes on standing, which are manifest by an increase or decrease in viscosity, is readily comprehensible on this basis.

The Structure of Gutta-Percha Based on Studies with Electron Rays

1934 ◽  
Vol 7 (4) ◽  
pp. 603-607 ◽  
Author(s):  
G. Bruni ◽  
G. Natta
Keyword(s):  
Organic Compounds ◽  
Structural Investigations ◽  
X Ray ◽  
Molecular Weights ◽  
Vegetable Fibers ◽  
Gutta Percha ◽  
Natural Organic Compounds ◽  
Ray Methods ◽  
Identity Period

Abstract Among the natural organic compounds with high molecular weights which have been the object of roentgenographic investigations with a view to determining their intimate constitution, rubber and other hydrocarbons of similar constitution such as gutta-percha and balata have been extensively studied in recent years. The results obtained with these substances by x-ray methods have however not been so complete and reliable as in the case of other products with high molecular weights, such as cellulose, found in nature in ramie and in certain vegetable fibers in forms which are particularly well oriented, which is of enormous advantage in structural investigations. Nevertheless, the roentgenographic results on rubber are of the greatest interest because from them it is possible to show that the molecules of rubber are oriented when the rubber is stretched or frozen, so that it can be proved that under these special conditions it has a sort of crystalline structure which is characterized by definite identity periods. The determination of the identity period in the direction of the fibers, which is 8.1 A. U., is particularly reliable.

Transmission Electron Microscopy of Protein Macromolecules

1971 ◽  
Vol 29 ◽  
pp. 424-425
Author(s):  
Henry S. Slayter
Keyword(s):  
Biological Systems ◽  
Metal Vapor ◽  
Resolving Power ◽  
Electron Microscopic ◽  
Chemical Methods ◽  
Molecular Weights ◽  
The Past ◽  
Physical Chemical ◽  
Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

Light Side of Design: Professional Vector

2020 ◽  
pp. 23-33
Author(s):  
Elena A. Zaeva-Burdonskaya ◽  
Yuri V. Nazarov
Keyword(s):  
Professional Practice ◽  
Wide Spectrum ◽  
Scientific Basis ◽  
Design Culture ◽  
Interdisciplinary Nature ◽  
Educational Programmes ◽  
Design Activities ◽  
The Subject ◽  
Light Side

This article addresses one of the most actively developing types of design activities – light design. The article comprises quotes of the leading Russian and foreign light design specialists published over the previous five years, as well as the authors’ own conclusions. The thoughts quoted in the article are sometimes opposite to each other and reflect the wide spectrum of professional practice. They reflect the initial opinions of analysts and experts which are often diverging. All of the specialists point at the interdisciplinary nature of the new profession, which imposes additional load on a designer overloaded enough already by the scope and speed of the problems being solved nowadays. The discussion of the new profession of light designer initiated on the pages of professional publications is especially important in view of the development of professional standards and standards of design and architectural education, as well as creation of new educational programmes based on various approaches to the subject in technical and humanitarian institutions. The goal of this article is to introduce light design into the field of fully legitimate sections of design culture, to define the authentic scientific basis of the new creative profession, to initiate a foundation for self-determination of the new synthetic area, which materially affects the state of the profession as a whole and the life standards of a wide variety of consumers. In order to reach the set goal, a comparative and analytical method of study was selected, which allows studying the problem to a large extent and from all angles and finding the ways of overcoming the challenges emerging in the area of the new activity.

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