A Statistical Treatment of Crystallization Phenomena in High Polymers

1942 ◽  
Vol 15 (3) ◽  
pp. 462-467
Author(s):  
T. Alfrey ◽  
H. Mark
Keyword(s):  
Free Energy ◽  
Melting Point ◽  
Crystallization Behavior ◽  
Amorphous Material ◽  
Statistical Treatment ◽  
Polymeric Materials ◽  
Crystalline Material ◽  
Crude Model ◽  
Temperature And Pressure ◽  
Degree Of Extension

Abstract An attempt has been made to explain the anomalous crystallization behavior of high polymeric materials on the basis of entropy changes in the amorphous material. The free energy of the amorphous phase depends not only on the temperature and pressure, but also on the degree of extension and the fraction of crystalline material in the sample. A crude model embodying these characteristics was proposed. On the basis of this model, it is possible to explain the unsharp melting point of rubber, the dependence of crystallization on the degree of extension, and the phenomenon of spontaneous extension.

scholarly journals Impact of Thermal Oxidation on Morphological, Structural and Magnetic Properties of Fe-Ni Wire-Like Nanochains

2021 ◽  
Author(s):  
Marcin Krajewski ◽  
Mateusz Tokarczyk ◽  
Sabina Lewińska ◽  
Kamil Bochenek ◽  
Anna Ślawska-Waniewska
Keyword(s):  
Magnetic Properties ◽  
Thermal Oxidation ◽  
Amorphous Material ◽  
Crystalline Material ◽  
Future Application ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Structural And Magnetic Properties ◽  
Source Of Information ◽  
The Magnetic Field

AbstractThis work presents the evolution of morphological, structural and magnetic properties of amorphous Fe-Ni wire-like nanochains caused by thermal oxidation. The initial Fe1−xNix samples (x = 0.75; 0.50; 0.25) were prepared through the magnetic-field-induced synthesis, and then they were heated in dry air at 400 °C and 500 °C. These treatments led to two competing simultaneous processes occurring in the investigated samples, i.e., (i) a conversion of amorphous material into crystalline material, and (ii) their oxidation. Both of them strictly affected the morphological and structural properties of the Fe-Ni nanochains which, in turn, were associated with the amount of iron in material. It was found that the Fe0.75Ni0.25 and Fe0.50Ni0.50 nanochains were covered during thermal treatment by the nanoparticle oxides. This coverage did not constitute a good barrier against oxidation, and these samples became more oxidized than the Fe0.25Ni0.75 sample which was covered by oxide nanosheets and contained additional Ni3B phase. The specific morphological evolutions of the Fe-Ni nanochains also influenced their saturation magnetizations, whereas their coercivities did not vary significantly. The obtained results constitute an important source of information for future application of the thermally treated Fe-Ni nanochains which could be applied in the energy storage devices or catalysis.

Exploring the Free Energy and Conformational Landscape of tRNA at High Temperature and Pressure

ChemPhysChem ◽  
2014 ◽  
Vol 16 (1) ◽  
pp. 138-146 ◽  
Author(s):  
Caroline Schuabb ◽  
Melanie Berghaus ◽  
Christopher Rosin ◽  
Roland Winter
Keyword(s):  
Free Energy ◽  
High Temperature ◽  
High Temperature And Pressure ◽  
Conformational Landscape ◽  
Temperature And Pressure

scholarly journals Application of reference-modified density functional theory: Temperature and pressure dependences of solvation free energy

2017 ◽  
Vol 39 (4) ◽  
pp. 202-217 ◽  
Author(s):  
Tomonari Sumi ◽  
Yutaka Maruyama ◽  
Ayori Mitsutake ◽  
Kenji Mochizuki ◽  
Kenichiro Koga
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Density Functional ◽  
Solvation Free Energy ◽  
Functional Theory ◽  
Temperature And Pressure

Mechanism of the Crystallization of High Polymers

1954 ◽  
Vol 27 (2) ◽  
pp. 374-384 ◽  
Author(s):  
G. Schuur
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Amorphous Material ◽  
Crystalline Polymer ◽  
Longitudinal Direction ◽  
Crystalline Material ◽  
Current View ◽  
X Ray ◽  
Made In ◽  
High Polymers

Abstract The crystallization of higher polymers is a phenomenon which is not yet fully understood, one of the main difficulties being to explain how the spherulites arise. An attempt will be made in this paper to draw a clearer picture of the mechanism of crystallization and thus to account for the origin of spherulites. It will then be seen how several other phenomena involved in the crystallization of natural rubber can be shown to be logically interrelated. The current view is that a crystalline polymer consists of a continuous amorphous phase containing small crystalline regions, the crystallites. The evidence as to the size of these crystallites, however, is at present inconclusive, because only the lower limit of their size can be measured by means of x-ray examination. The reason is that, owing to the absence of reflections of a higher order, the effect of irregularities in the crystallites and of the heat motion of the molecules cannot be measured separately. Another doubtful question is whether the small angle interference maxima are to be interpreted as a measure of mean distances between the crystallites. To do this, Wallner has to resort to the assumption that the crystallites are unstable, whereas it is presumed, on the evidence of the mechanical properties of the high polymers, that a crystallite is stable and permanent. Hoffmann found 82 ± 7 per cent of crystalline material in polychlorotrifluoroethylene and Buckley, Cross, and Ray found as much as 95 per cent in polymethylene. Such high percentages make it doubtful whether the crystalline phase can be discontinuous at all. In this article any volume of material in which the molecules lie parallel is called a crystallite. The direction in which the molecules are oriented is termed the longitudinal direction of the crystallite. It is immaterial to the argument whether a crystallite consists of several crystallites, aligned in parallel separated by a small amount of amorphous material, or of a single crystallite containing large irregularities.

Exploring the influence of natural cosolvents on the free energy and conformational landscape of filamentous actin and microtubules

2018 ◽  
Vol 20 (45) ◽  
pp. 28400-28411 ◽  
Author(s):  
Paul Hendrik Schummel ◽  
Michel W. Jaworek ◽  
Christopher Rosin ◽  
Jessica Högg ◽  
Roland Winter
Keyword(s):  
Free Energy ◽  
Significant Influence ◽  
Filamentous Actin ◽  
Conformational Landscape ◽  
Temperature And Pressure

Natural osmolytes have a significant influence on the temperature- and pressure-dependent stability of filamentous actin and microtubules.

New Aspects on Melting and Annealing Behaviour of Polymers

1978 ◽  
Vol 33 (12) ◽  
pp. 1472-1483
Author(s):  
J. Haase ◽  
S. Köhler ◽  
R. Hosemann
Keyword(s):  
Free Energy ◽  
Melting Point ◽  
Partial Melting ◽  
Surface Free Energy ◽  
Average Crystallite Size ◽  
X Ray ◽  
State Diffusion ◽  
Crystallite Sizes ◽  
Dta Curves ◽  
Dta Curve

Abstract Poly( 1-butene) (PB) crystallizes from the melt in a metastable modification II (mod. II) which slowly transforms into the stable modification I (mod. I). X-ray wide angle (WAXS) measurements show that in mod. I the size of the microparacrystallites (mPC’s) in chain direction, D̅012, the polydispersity gD of the size distribution in this direction, the lateral size D̅110 and the paracrystalline g110-value do not change upon annealing at temperatures up to the melting point. In mod. II, however, the sizes D̅012 and D̅110 increase with rising annealing temperature Tann. At a certain Tann and beyond a sufficient annealing time tann the size D̅012 shows a logarithmic increase with tann whereas D̅110 stays constant. Measuring melting points Tm of mod. I-samples, we found a linear relationship between Tm and 1/D̅012 according to the Thomson equation resulting in a melting point for an infinite crystal of Tm∞ (mod. I) = 139 °C and a mean surface free energy of σ̅e′̅ (mod. I) = 47 ergs/cm2. T m versus 1/D̅012 for mod. II is linear only for high D̅012-values yielding Tm∞ (mod. II) = 130 °C and σ̅e′̅ (mod. II) = 29 ergs/cm2. However, a partially molten and afterwards quenched sample of mod. I with small mPC’s shows a mod. II-peak which fits the straight line extrapolated from the large D̅012-values. The DTA curves of mod. I-samples shift to higher temperatures and narrow after annealing although the crystallite sizes and size distributions remain as well as the paracrystalline distortions the same. X-ray and DTA measurements eliminate therefore surface premelting and selective melting of thinner and more distorted lamellae in mod. I. Upon annealing this modification, σ̅e′̅ decreases from 47 ergs/cm2 to 15 ergs/cm2 and the distribution of σe′ narrows. The latter determines predominantly the shape of the DTA curve. The Thomson equation therefore, applied to different samples links only the average crystallite size and the mean surface free energy with the melting point. In mod. I partial melting occurs independent of D̅012 and starts mainly at those mPC’s which have exposed surfaces with high σe′. At the beginning only single mPC’s or single lamellae melt, but no bundles of lamellae. The logarithmic increase of D̅012 in mod. II with tann can be explained according to Hosemann’s model of “lateral melting” also by a partial melting of mPC’s with unprotected lateral surfaces and by a consecutive solid state diffusion of their chainsegments into the two mPC’s adjacent in chain direction, increasing the averaged sizes of the long period and the lamellae thickness.

The thermal fission-induced crystalline-to-amorphous transformation in U6Fe

1988 ◽  
Vol 3 (3) ◽  
pp. 453-460 ◽  
Author(s):  
Don M. Parkin ◽  
Reed O. Elliott
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystallization Behavior ◽  
Amorphous Material ◽  
Nucleation And Growth ◽  
Local Defect ◽  
Scanning Calorimetry ◽  
Dose Dependent ◽  
Limited Process ◽  
Total Resistivity ◽  
Crystalline Matrix

The crystalline-to-amorphous transformation in U6Fe produced by thermal fission fragment damage was studied using resistivity and differential scanning calorimetry. The results are described in terms of a model of radiation-produced defect buildup in the crystalline matrix followed by transformation of small regions to an amorphous phase when a critical local defect concentration is reached. This can occur directly in a single cascade or from cascade overlap. The total resistivity is modeled assuming an inhomogeneous media consisting of a crystalline matrix containing a dose-dependent concentration of defects and amorphous zones. The crystallization behavior is initially, starting at Tc = 388 K, a kinetically limited process of shrinkage of amorphous zones that gradually transforms to nucleation and growth in fully amorphous material at Tc = 555 K.

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