X-Ray Spectrography of Polymers and in Particular Those Having a Rubber-like Extensibility

1936 ◽  
Vol 9 (3) ◽  
pp. 357-372 ◽  
Author(s):  
J. R. Katz
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Good Deal ◽  
Small Unit ◽  
Chain Molecules ◽  
X Ray ◽  
The Subject ◽  
Chain Form ◽  
Long Chain

Abstract For many years Staudinger defended the theory that polymers have—in the simplest ease—a long chain form of molecules, in which a certain small unit repeats itself regularly along the chain, the units being united by primary valencies. His arguments were not, however, at the beginning of 1927, sufficiently convincing. The decisive argument was forthcoming shortly afterwards by the application of x-ray spectrography. I would like to begin this article by bringing a few personal memories about this development. At the meeting of the Naturforscherversammlung in Innsbruck in September, 1924, I first heard him defend this theory, especially for the ease of polyoxymethylenes, but also for some other cases. Neither I myself nor some others to whom I spoke were convinced by his very interesting exposition. His conception seemed possible, but, many of us thought, not proved. And the whole subject did not yet look attractive to many of us. At the meeting of the Naturforscherversammlung in Düsseldorf in September, 1926, where a symposium on high molecular weight substances was held, he again defended this theory. In 1926, the interest in the subject had already increased a good deal, as is clearly shown by the fact that a symposium on the subject had been arranged. Yet, Staudinger's conceptions did not seem to many of us really convincing, nor was the decisive value which x-ray spectrography could have for the subject yet understood at this meeting. Under these circumstances there can be little doubt that the priority of the idea of the long chain molecules for polymers is chiefly due to Staudinger.

Behavior of Rubber Hydrocarbon in a Molecular Still

1939 ◽  
Vol 12 (4) ◽  
pp. 789-793 ◽  
Author(s):  
W. Harold Smith ◽  
Henry J. Wing
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
High Molecular Weight ◽  
Molecular Species ◽  
Decomposition Temperature ◽  
Sedimentation Equilibrium ◽  
Chain Molecules ◽  
Molecular Weights ◽  
Average Value ◽  
Long Chain

Abstract Some investigators believe that rubber consists of associated molecules, and others accept Staudinger's view that long-chain molecules are formed by polymerization. Pummerer, Andriessen and Gündel have obtained a molecular weight as low as 600. Meyer and Mark believe that it is approximately 5,000, although they calculated on the basis of osmotic pressures values as high as 350,000. They, as well as Pummerer, consider that rubber is an associated colloid and that high molecular weights are caused by aggregates, sometimes called micelles. Staudinger, however, considers that the long-chain rubber molecule itself has a molecular weight of 200,000 or even 350,000, and that products with lower values, which may be formed in rubber, result from degradation. if the molecules are small it might be possible to distil them if their vapor pressure could be sufficiently increased, but none would distil without decomposition if the molecules are very large. Because the vapor pressure of rubber below its decomposition temperature is low, it appeared of interest to attempt to distil the material in a molecular still. Paraffin wax and sugar, both substances of relatively high molecular weight, have been successfully distilled in this type of apparatus. Subsequent to the work described in this paper, the molecular weight of sol rubber prepared at this Bureau was determined by Kraemer and Lansing of E. I. du Pont de Nemours & Co., Inc. They used the Svedberg method of sedimentation equilibrium in an ultracentrifuge with ethereal solutions of sol rubber. The temperature of the solutions during determinations was approximately 10° C, and an average value of 460,000 was obtained. There was evidenced of a mixture of molecular species.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

PHOTOCATALYTIC DEGRADATION OF PYRENE IN POROUS Pt/TiO2–SiO2 PHOTOCATALYST SUSPENSION UNDER UV IRRADIATION

NANO ◽  
2008 ◽  
Vol 03 (05) ◽  
pp. 317-322 ◽  
Author(s):  
ZHAOHUI LUO ◽  
KEIKO KATAYAMA-HIRAYAMA ◽  
KIMIAKI HIRAYAMA ◽  
TETSUYA AKITSU ◽  
HIDEHIRO KANEKO
Keyword(s):  
Molecular Weight ◽  
Photocatalytic Degradation ◽  
High Molecular Weight ◽  
Uv Irradiation ◽  
Degradation Kinetics ◽  
Degradation Process ◽  
Bet Surface Area ◽  
Experimental Conditions ◽  
Initial Concentration ◽  
X Ray

Pyrene is a high molecular weight polycyclic aromatic hydrocarbon (PAH) that is found in water systems worldwide. It is harmful to living organisms, even when taken in very small amounts. The photocatalytic degradation of pyrene in porous Pt / TiO 2– SiO 2 photocatalyst (PPtPC) suspension under UV irradiation was investigated in this study. PPtPC was prepared by a simple heat treatment of the compacted powder mixtures of anatase TiO 2 and amorphous SiO 2 with camphor as a pore directing template, followed by coating platinum by the dip-coating method. X-ray diffraction (XRD), scanning electron microscopy (SEM) with an integrated energy-dispersive analysis of the X-ray (EDX) system, and Brunauer–Emmett–Teller (BET) were used to characterize PPtPC. The degradation kinetics of pyrene in different experimental conditions, such as initial concentration of pyrene, oxygen concentrations, pH, and temperature, were investigated. The durability of PPtPC was also tested. The results indicate that the structure of TiO 2 in PPtPC is anatase. The aggregated size of PPtPC is in the range of 10–100 μm, the mean pore diameter is 3 nm, and the BET surface area is 109 m2 g-1. The photocatalytic degradation process of pyrene follows pseudo-first-order kinetics. The rate constants increase as the initial concentration of pyrene and pH decrease. Higher temperature slightly enhances the rate constant. The dissolved oxygen in the photocatalytic degradation process is not as important as in the photolysis process. The recovered PPtPC still shows high photoactivity. This work suggests that PPtPC offers a promising method for high molecular weight PAH removal.

Commercial Immunodepleted Deficient Plasmas Contain Cleaved High Molecular Weight Kininogen (HK)

1988 ◽  
Vol 60 (03) ◽  
pp. 447-452
Author(s):  
C Mannhalter ◽  
H Lang
Keyword(s):  
Molecular Weight ◽  
Quality Control ◽  
Comparative Analysis ◽  
High Molecular Weight ◽  
Control Method ◽  
Immunoblot Analysis ◽  
High Molecular Weight Kininogen ◽  
Single Chain ◽  
Quality Control Method ◽  
Chain Form

SummaryComparative analysis of high molecular weight kininogen (HK) in various commercial congenital and immunodepleted deficiency plasmas was performed by immunoblotting of HK. It was found, that some artificially depleted deficiency plasmas contained proteolytically cleaved, kinin-free kininogen. In contrast, in all congenitally deficient plasmas, HK was present in the intact, single chain form. Thus, cleavage of kininogen could have been triggered by or during the immunodepletion procedure. It was seen, that the degree of proteolytic cleavage and degradation of HK in depleted plasmas differed among various manufacturers. E.g. depleted products of one company contained only trace amounts of cleaved HK, in contrast to products of another one, in which HK was completely degraded. The immunoblot analysis of HK reflects the occurrence of proteolytic events during the production of artificially deficient plasmas and can therefore serve as a quality control method.

scholarly journals Structure of stretched rubber.

1938 ◽  
Vol 164 (919) ◽  
pp. 491-496 ◽  
Author(s):  
C. J. Birkett Clews ◽  
F. Schoszberger ◽  
William Lawrence Bragg
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Pictorial Representation ◽  
Alternative Theory ◽  
Crystalline Region ◽  
Double Refraction ◽  
Micellar Structure ◽  
X Ray

Investigations of the micellar structure of fibre substances have given rise to two theories. The older theory (Meyer and Mark 1930; Mark 1932; Siefriz 1934; Meyer 1930; and Nageli 1928) considers the micelles as separate crystallites, between which lie the intermicellar spaces. The micelles consist of “Hauptvalenzketten” bound together along their length by homeopolar bonds and in the transverse direction by van der Waals’ forces, the intermicellar binding being also attributed to van der Waals’ forces. The original model suggested in work published by K. H. Meyer (1930), for cellulose, depicts the micelles arranged like bricks in a wall (fig. 1), and doubtless this is the simplest explanation of the X-ray results. But it is difficult to understand how such an arrangement can give a micellar structure its peculiar mechanical properties, and further how it is possible, when both inter- and intramicellar cohesion are attributed to the same type of force, to cause by swelling experiments an enlargement of the intermicellar spaces, while the “Hauptvalenzketten” remain unaffected. An alternative theory has been put forward by O. Gerngross, K. Herrmann and W. Abitz (1930), W. T. Astbury (1933), A. Frey-Wyssling (1936) and E. Guth and S. Rogowin (1936). These authors suppose that a given “Hauptvalenzkette” is not confined to a single crystalline region but may stretch through more such regions. In general, the arrangement of the neighbouring chains will be truly lattice-like, but a chain may lie at too great a distance from its neighbours or not lie exactly parallel to them, so that the structure as a whole will show statistically distributed spaces. In fig. 2 ordered crystalline regions may be distinguished (drawn in thick line), but their significance is physically different from that of the crystallites of the Meyer model. They are not self-contained units; the whole system is linked together due to the “Hauptvalenzketten” extending beyond a single micelle. Astbury considers that in a substance of high molecular weight of a type capable of swelling that part which produces the X-ray spectrum is the concentration centre of a complicated network of thread-like molecules. He draws an analogy between micellar structure and the secondary structure of Zwicky. He suggests that it is possible that micellar systems, which are characterized by a mixture of perfection and imperfection, are the counterpart in compounds of high molecular weight of the well-known mosaic structure of the more familiar crystals. Frey-Wyssling is of the opinion that the micelles, growing together, enclose lens-shaped spaces running parallel to the fibre axis. Between these intermicellar spaces are small rod-shaped regions of undistorted lattice, which are the so-called micelles of the earlier work (fig. 3). In this figure, which gives a pictorial representation of Frey’s theory, the statistically distributed hollow spaces are shown black; some of these are enclosed in undistorted crystalline regions. A lamellar structure consisting of superimposed monomolecular layers suggested by O. L. Sponsler and W. H. Dore (1930) has been shown to be untenable from the work on double refraction by Baas-Becking and Galliher (1931).

Ligand-Unsymmetrical Phenoxyiminato Dinickel Catalyst for High Molecular Weight Long-Chain Branched Polyethylenes

2015 ◽  
Vol 4 (11) ◽  
pp. 1297-1301 ◽  
Author(s):  
Dongxu Shu ◽  
Aidan R. Mouat ◽  
Casey J. Stephenson ◽  
Anna M. Invergo ◽  
Massimiliano Delferro ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Long Chain

scholarly journals On the stability of unimolecular films. Part II.-The mechanism of film expansion

1929 ◽  
Vol 124 (794) ◽  
pp. 333-343 ◽  
Keyword(s):  
Aqueous Solution ◽  
Condensed State ◽  
Head Group ◽  
Chain Molecules ◽  
X Ray ◽  
Characteristic Area ◽  
The Stability ◽  
Contraction And Expansion ◽  
Long Chain ◽  
Hydrion Concentration

In Part I it was shown that the adhesion of a unimolecular film of a fatty acid to an underlying aqueous solution could be varied by alteration of the Hydrion concentration of the solution. Increasing the alkalinity effected an increase in the adhesional force of the polar beads, and under isothermal con­ditions a film could be converted from the expanded to the liquid condensed and even to the solid condensed state, by causing an increase in these adhesional forces, this process being perfectly reversible. Whilst ionisation of the acid occurs over a bruited range of P H , the alteration in adhesional forces by a change in P H and the effects of such change on the state of the film extend, contrary to the conclusions of Egner and Hägg,* over a much wider range of P H . Since contraction and expansion of the film coincide with an increase decrease respectively in the adhesional forces holding the polar heads to the surface, we may inter that expansion is effected by a gradual tilting of the molecules from the close packed formation existing in the solid condensed state. We have noted that Müller* from X-ray determinations on crystals of fatty acids suggested that it seemed possible that even in a film in the solid condensed state the molecules were already tilted. Objections to this view were raised by Adam, since he found but one characteristic area for long chain molecules in the solid condensed state, which was, with few exceptions, independent of the nature of the head group. He further found that the area in the liquid condensed state*was dependent on the nature of the head group.

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