scholarly journals The structure of polychloroprene

1942 ◽  
Vol 180 (980) ◽  
pp. 100-107 ◽  
Keyword(s):  
Physical Properties ◽  
Crystalline Structure ◽  
Light Treatment ◽  
Unit Cell ◽  
Cross Linking ◽  
Chain Molecules ◽  
X Ray ◽  
Before And After ◽  
Ray Methods ◽  
Long Chain

Specimens of polychloroprene before and after light treatment have been examined by X -ray methods. There is no change in the crystalline structure, although there are differences in the physical properties ascribed to cross-linking of the long-chain molecules. The unit cell is possibly ortho­rhombic: a = 8·90 A , b = 4·70 A, c = 12·21 A, and contains four chloroprene (C 4 H 5 Cl) units.

The Structure of Polychloroprene

1942 ◽  
Vol 15 (4) ◽  
pp. 847-853
Author(s):  
C. J. Birkett Clews
Keyword(s):  
Physical Properties ◽  
Crystalline Structure ◽  
Spatial Configuration ◽  
Unit Cell ◽  
Cross Linking ◽  
X Ray ◽  
Ray Density ◽  
Pass Through ◽  
Ray Methods ◽  
Identity Period

Abstract Specimens of polychloroprene and light-treated polychloroprene have been examined by x-ray methods. There is evidently no change in the crystalline structure of the two substances, although there are differences in physical properties which are ascribed to cross-linking of the long polychloroprene chains. This conclusion is confirmed by the x-ray work. The unit cell of polychloroprene is probably orthorhombic, with dimensions a=8.90 A.U., b=4.70 A.U., c=12.21 A.U. From the experimentally determined density of 1.086 g. per cc, it is deduced that there are four chloroprene units in the cell. The x-ray density (for the stretched material) is 1.14 g. per cc. The long chains lie parallel to the b-axis (the direction of stretching), and four of these chains pass through the unit cell. It is concluded, from the identity period, that the chain is not planar and a possible spatial configuration is given.

An X-Ray Investigation of Crystallinity in Rubber

1939 ◽  
Vol 12 (4) ◽  
pp. 706-718
Author(s):  
S. D. Gehman ◽  
J. E. Field
Keyword(s):  
Crystalline Structure ◽  
Polymeric Materials ◽  
The Other ◽  
X Ray Diffraction ◽  
Random Orientation ◽  
Chain Molecules ◽  
Micellar Structure ◽  
X Ray ◽  
Recent Developments ◽  
Long Chain

Abstract The crystalline structure which rubber exhibits under certain circumstances has come to be regarded as associated with a secondary or micellar structure of long chain molecules. The exact mechanism by which the localized ordered regions appear is a speculative subject in recent developments of the micellar theory of long chain polymeric materials. The views of various workers on this subject have been summarized by other authors. The crystalline structure of rubber displays varying degrees and types of orientation of the crystal units, depending on the conditions under which crystallization occurs. The amorphous x-ray diffraction pattern of unstretched rubber is shown in Figure 1, the unoriented crystalline diagram for frozen rubber in Figure 2. When crystallization is induced by stretching, the crystallites are aligned along the axis of stretching, giving the fiber diagrams of Figures 3 and 4. In this case there is random orientation of the other two axes of the crystallites. “Higher orientation,” in which all three axes of the crystallites are aligned, gives the diagram of Figure 15 and can be secured with suitable dimensions of the stretched piece.

Observations on the X-Ray Structure of Rubber and the Size and Shape of Rubber Crystallites

1944 ◽  
Vol 17 (3) ◽  
pp. 640-652
Author(s):  
S. D. Gehman ◽  
J. E. Field
Keyword(s):  
Molecular Structure ◽  
Physical Properties ◽  
X Ray Diffraction ◽  
Ray Method ◽  
Chain Molecules ◽  
X Ray ◽  
Rubberlike Material ◽  
Molecular Forces ◽  
Ray Patterns ◽  
Long Chain

Abstract In former times, we used to be painfully aware of the shortcomings and elastic imperfections of Hevea rubber. With its disappearance, we have come to think of it as having an ideal balance in physical properties for a rubberlike material which it has been difficult to approach with synthetic polymers. for this reason, it is still important to investigate the molecular structure of Hevea rubber and to try to understand the characteristics of this structure which are responsible for its physical properties. X-Ray diffraction methods can be applied to the problem of the molecular structure of Hevea rubber and a few synthetic rubbers, such as Butyl rubber and Neoprene, because crystallization occurs upon stretching. A detailed description of the x-ray diffraction results with rubber is available in a review article and need not be repeated here. It should be pointed out that the story obtained from the x-ray structure is not complete because there are important aspects of the structure which are not revealed by this means. It is not possible to measure directly the length of the chain molecules. The nature of the amorphous phase, such as the system of cross-linking of the long chain molecules on vulcanization, does not become evident in x-ray patterns. The physical properties of Hevea rubber must depend on a delicate balance of primary and secondary valence forces. The x-ray method does not permit any direct measurement of these forces but merely shows the geometrical arrangement which results from the molecular forces. Even with these limitations, much valuable information can be secured on the nature of the molecular rearrangements which occur upon stretching. Deductions can be drawn from the x-ray diffraction results regarding the form and spatial relationships of the long chain polymeric molecules and the manner in which they interact under stress. Correlations can then be looked for between the crystallization and the physical properties.

Über die Kristallstruktur von KSc2 F7 / The Crystal Structure of KSc2 F7

1985 ◽  
Vol 40 (6) ◽  
pp. 726-729 ◽  
Author(s):  
Klaus Güde ◽  
Christoph Hebecker
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Unit Cell ◽  
Space Group ◽  
X Ray ◽  
Monoclinic Unit Cell ◽  
R Value ◽  
Ray Methods

Abstract Single crystals of KSc2F7 have been prepared from a mixture of KF and ScF3 . The samples were investigated by X-ray methods. KSc2F7 crystallizes orthorhombically with a = 10.643(2), b = 6.540(1), c = 4.030(1) Å. These data indicate a close crystallographic connection to the monoclinic unit cell of KIn2F7 [1], But in contrast to KIn2F7 , KSc2 F7 crystallizes in space group No. 65. Cmmm - D192h. The R-value for 341 observed independent reflections is 0.060.

scholarly journals X-ray studies of the structure of hair, wool, and related fibres.- I. General

1931 ◽  
Vol 230 (681-693) ◽  
pp. 75-101 ◽  
Keyword(s):  
Physical Properties ◽  
Crystalline Structure ◽  
Human Hair ◽  
X Rays ◽  
Present Communication ◽  
Cellulose Fibres ◽  
X Ray ◽  
Usual Manner ◽  
Wide Range ◽  
Muscle Nerve

It is now some ten years since it was first realised that, in common with natural and artificial cellulose fibres, animal fibres with a protein basis are in many cases sufficiently crystalline to yield a pronounced interference figure when examined with monochromatic X-rays. Such “ X-ray fibre diagrams ” were reported in 1921 by HERZOG and JANCKE* for muscle, nerve, sinew, and hair, and in 1924 similar photographs from human hair were obtained by one of the present writers. From an X-ray examination of wool it was concluded by THREADGOLD that “ there is no evidence for assuming the wool fibres and yarns examined to have a crystalline structure,” but in 1927 EWLES and SPEAKMAN had already obtained wool interference figures precisely similar to those previously obtained from hair. The two last-named authors endeavoured to interpret their results in the light of certain physical properties, but it has since become clear that the problem of hair structure is sufficiently complex to necessitate an X-ray study of a wide range of materials under as great a variety of conditions as possible. The present communication is an account of the preliminary results of such an investigation. Over a hundred X-ray photographs have been taken, using copper K-radiation filtered of the MATHS FORMULA line by nickel foil about 1/100 mm. thick. The “ slit” was a rectangular aperture, 4 cm. x 0.5mm., the scattered rays from which were screened off in the usual manner by a secondary slit.

Crystalline Structure and the Role of Low-Temperature-Deposited AlN and GaN on Sapphire Revealed by X-Ray CTR Scattering and X-Ray Reflectivity Measurements

2003 ◽  
Vol 10 (02n03) ◽  
pp. 537-541 ◽  
Author(s):  
Y. Takeda ◽  
M. Tabuchi ◽  
H. Amano ◽  
I. Akasaki
Keyword(s):  
Low Temperature ◽  
Crystalline Structure ◽  
Thin Layers ◽  
X Ray ◽  
Atomic Force ◽  
Crystal Truncation Rod ◽  
Before And After ◽  
Afm Observation

Crystalline and morphological quality of low-temperature (LT)-deposited and annealed AlN and GaN thin layers were investigated by X-ray crystal truncation rod (CTR) scattering and X-ray reflectivity measurements and atomic force microscope (AFM) observation. It was revealed that the LT-AlN layer was more uniform in terms of the crystalline structure and the layer thickness than the LT-GaN layer, before and after annealing. It suggests that LT-AlN is more suitable as a buffer layer between sapphire substrate and GaN.

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.

The Rubber-like Behavior of an Artificial Substance (Oppanol) when Irradiated with X-rays

1938 ◽  
Vol 11 (4) ◽  
pp. 687-688
Author(s):  
R. Brill ◽  
F. Halle
Keyword(s):  
Natural Rubber ◽  
Normal State ◽  
X Rays ◽  
Organic Substances ◽  
Chain Molecules ◽  
X Ray ◽  
Natural Substances ◽  
Amorphous Sulfur ◽  
Definite Temperature ◽  
Long Chain

Abstract As is known, natural rubber has the property of giving, when stretched, an x-ray fiber diagram, whereas in a normal state the same rubber is amorphous. Numerous other natural substances such as hair and tendon, and artificial substances such as polychloroprene, behave in the same way. However, this effect is not confined to purely organic substances, and it is to be found, for example, in the case of so-called amorphous sulfur and polyphosphornitryl chloride (PNCl2)x. All these substances have the property in common with one another of exhibiting a rubber-like elasticity within a definite temperature range, and of being composed of long-chain molecules.

Physical Properties of Composite Membrane Containing Apatite and Poly-Lactic Acid /Poly-Glycolic Acid Copolymer In Vitro

2005 ◽  
Vol 284-286 ◽  
pp. 749-752
Author(s):  
T. Watanabe ◽  
Seiji Ban ◽  
Toshiki Itoh ◽  
Shozo Tsuruta ◽  
Takahiro Kawai ◽  
...  
Keyword(s):  
Physical Properties ◽  
Composite Membrane ◽  
Body Fluid ◽  
Glycolic Acid ◽  
Poly Lactic Acid ◽  
X Ray ◽  
Acid Copolymer ◽  
Before And After

The purpose of this study was to evaluate the physical properties of the composite membrane before and after soaking in simulated body fluid (SBF) and discuss both degradation and maintenance of their properties. Before and after soaking in SBF, some deposits were found on the preexisted apatite crystals, and Ca and P were mainly detected by energy dispersive X-ray analyzer (EDX). Our results suggest that the composite membrane consisting of apatite and the biodegradable PLGA copolymer would have excellent biocompatibility and maintain adequate physical properties for in vivo use.

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