scholarly journals Lamellar thickness in semicrystalline polymers as a result of the competition between crystal growth and intracrystalline chain dynamics

2021 ◽  
Author(s):  
Martha Schulz ◽  
Mareen Schulz ◽  
Kay Saalwächter ◽  
Thomas Thurn-Albrecht
Keyword(s):  
Decisive Role ◽  
Semicrystalline Polymers ◽  
Lamellar Thickness ◽  
Polarization Microscopy ◽  
Chain Dynamics ◽  
X Ray Scattering ◽  
Special Cases ◽  
Lamellar Crystals ◽  
Nmr Methods ◽  
First Time

Abstract The non-equilibrium thickness of lamellar crystals in semicrystalline polymers varies largely between different polymer systems and depends on the crystallization temperature Tc. There is currently no consensus on the mechanism of thickness selection. Previous work has highlighted the decisive role of intracrystalline chain dynamics (ICD) in special cases, but a systematic dependence of lamellar thickness on relevant timescales such as that of ICD and stem attachment has not yet been established. Studying the morphology by small-angle X-ray scattering and the two timescales by NMR methods and polarization microscopy, we here present data on poly(oxymethylene), a case with comparably slow ICD. It fills the gap between previously studied cases of absent and fast ICD, enabling us to establish for the first time a quantitative dependence of lamellar thickness on the competition between the noted timescales.

scholarly journals Competition between crystal growth and intracrystalline chain diffusion determines the lamellar thickness in semicrystalline polymers

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Martha Schulz ◽  
Mareen Schäfer ◽  
Kay Saalwächter ◽  
Thomas Thurn-Albrecht
Keyword(s):  
Decisive Role ◽  
Semicrystalline Polymers ◽  
Lamellar Thickness ◽  
Polarization Microscopy ◽  
Polymer Systems ◽  
X Ray Scattering ◽  
Special Cases ◽  
Lamellar Crystals ◽  
Nmr Methods

AbstractThe non-equilibrium thickness of lamellar crystals in semicrystalline polymers varies significantly between different polymer systems and depends on the crystallization temperature Tc. There is currently no consensus on the mechanism of thickness selection. Previous work has highlighted the decisive role of intracrystalline chain diffusion (ICD) in special cases, but a systematic dependence of lamellar thickness on relevant timescales such as that of ICD and stem attachment has not yet been established. Studying the morphology by small-angle X-ray scattering and the two timescales by NMR methods and polarization microscopy respectively, we here present data on poly(oxymethylene), a case with relatively slow ICD. It fills the gap between previously studied cases of absent and fast ICD, enabling us to establish a quantitative dependence of lamellar thickness on the competition between the noted timescales.

Mesoscopic structure of SiC fibers by neutron and x-ray scattering

1996 ◽  
Vol 11 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Kentaro Suzuya ◽  
Michihiro Furusaka ◽  
Noboru Watanabe ◽  
Makoto Osawa ◽  
Kiyohito Okamura ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Volume Fraction ◽  
X Rays ◽  
X Ray ◽  
Sic Fibers ◽  
X Ray Scattering ◽  
Mesoscopic Structure ◽  
Angle Scattering ◽  
Momentum Transfer Range ◽  
First Time

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

scholarly journals Nella terra dei Vichinghi

2006 ◽  
Vol 1 (2) ◽  
Author(s):  
Italo Balbo
Keyword(s):  
Air Force ◽  
Spanish Civil War ◽  
Decisive Role ◽  
The United States ◽  
Weapons Of Mass Destruction ◽  
Mass Destruction ◽  
Political Movement ◽  
Fascist Regime ◽  
High Level ◽  
First Time

Icelandic translation of a chapter from the book describing Italo Balbo's 1933 journey to Chicago with a hundred Italians on twenty-four seaplanes. As recalled in the essays available in the first issue of Nordicum-Mediterraneum, they flew from Italy to the United States, stopping in Iceland on their way. The book La centuria alata was published also in order to exploit his own growing fame as an aviator in view of a high-level political career inside the Italian fascist regime. Being a fascist since the early days of Mussolini's political movement, Balbo led the blackshirt militia in many violent actions directed against democratic politicians. After the notorious "March on Rome" (1922) and the establishment of Mussolini's regime, he played a decisive role in developing the Italian air force, testing for the first time also new weapons of mass destruction, especially during the Spanish Civil War.

scholarly journals Enzyme-hydrolyzed Fruit of Jurinea mollis: A Rich Source of (-)-(8R,8′R)-Arctigenin

2016 ◽  
Vol 11 (10) ◽  
pp. 1934578X1601101 ◽  
Author(s):  
Rita Könye ◽  
Ágnes Evelin Ress ◽  
Anna Sólyomváry ◽  
Gergő Tóth ◽  
András Darcsi ◽  
...  
Keyword(s):  
Low Energy ◽  
Plant Tissues ◽  
Selective Isolation ◽  
Isolation Method ◽  
Specific Accumulation ◽  
Fruit Wall ◽  
Lignan Glycoside ◽  
Nmr Methods ◽  
First Time ◽  
Low Energy Conformations

In Jurinea mollis fruit, the dibenzylbutyrolactone-type lignan glycoside arctiin and its aglycone arctigenin were determined for the first time using a combination of optimized enzymatic treatment and complementary spectrometric (HPLC-MS, GC-MS) and spectroscopic (CD and NMR) methods. Analysis of separated fruit parts, i.e., the fruit wall and embryo, demonstrated the specific accumulation of arctiin, since it was exclusively found in the embryo. Arctiin in the embryo samples (71.5 mg/g) was found to be quantitatively converted into arctigenin (50.7 mg/g) by endogenous enzymatic hydrolysis, resulting in one of the highest arctigenin-containing plant tissues reported to date and allowing the selective isolation of arctigenin by our recently reported three-step isolation method. The absolute configuration of the isolated arctigenin was determined to be (-)-(8 R,8′ R). Conformational analysis of arctigenin was also performed, resulting in three major low energy conformations.

Grazing-incidence X-ray scattering of lamellar thin films

2019 ◽  
Vol 52 (2) ◽  
pp. 247-251
Author(s):  
Detlef-M. Smilgies
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Small Molecules ◽  
Film Studies ◽  
Grazing Incidence ◽  
Semicrystalline Polymers ◽  
X Ray ◽  
X Ray Scattering ◽  
Incident Plane ◽  
Ray Scattering

Recently, surface and thin-film studies using area detectors have become prevalent. An important class of such systems are lamellar thin films formed by small molecules, liquid crystals or semicrystalline polymers. Frequently, the lamellae align more or less parallel to the substrate. Such structures can be easily discerned by their characteristic X-ray scattering close to the incident plane. This paper describes how such patterns can be simulated, in order to extract morphological information about the thin film.

scholarly journals Unusual packing of soft-shelled nanocubes

2019 ◽  
Vol 5 (5) ◽  
pp. eaaw2399 ◽  
Author(s):  
Fang Lu ◽  
Thi Vo ◽  
Yugang Zhang ◽  
Alex Frenkel ◽  
Kevin G. Yager ◽  
...  
Keyword(s):  
Decisive Role ◽  
Anisotropic Shell ◽  
Particle Packing ◽  
Body Centered Cubic ◽  
X Ray ◽  
X Ray Scattering ◽  
Cubic Phases ◽  
Shaped Nanoparticles ◽  
Soft Shell ◽  
Packing Effects

Space-filling generally governs hard particle packing and the resulting phases and interparticle orientations. Contrastingly, hard-shaped nanoparticles with grafted soft-ligands pack differently since the energetically interacting soft-shell is amenable to nanoscale sculpturing. While the interplay between the shape and soft-shell can lead to unforeseen packing effects, little is known about the underlying physics. Here, using electron microscopy and small-angle x-ray scattering, we demonstrate that nanoscale cubes with soft, grafted DNA shells exhibit remarkable packing, distinguished by orientational symmetry breaking of cubes relative to the unit cell vectors. This zigzag arrangement occurs in flat body-centered tetragonal and body-centered cubic phases. We ascribe this unique arrangement to the interplay between shape and a spatially anisotropic shell resulting from preferential grafting of ligands to regions of high curvature. These observations reveal the decisive role played by shell-modulated anisotropy in nanoscale packing and suggest a plethora of new spatial organizations for molecularly decorated shaped nanoparticles.

scholarly journals Lévy Distributions for One-Dimensional Analysis of the Bose–Einstein Correlations

2017 ◽  
Vol 2017 ◽  
pp. 1-18 ◽  
Author(s):  
V. A. Okorokov
Keyword(s):  
Reasonable Agreement ◽  
Emission Region ◽  
General Study ◽  
Gaussian Distributions ◽  
One Dimensional ◽  
Interaction Processes ◽  
Special Cases ◽  
Centrally Symmetric ◽  
Bose Einstein ◽  
First Time

A general study of relations between the parameters of two centrally symmetric Lévy distributions, often used for one-dimensional investigation of Bose–Einstein correlations, is given for the first time. These relations of the strength of correlations and of the radius of the emission region take into account possible various finite ranges of the Lorentz invariant four-momentum difference for two centrally symmetric Lévy distributions. In particular, special cases of the relations are investigated for Cauchy and normal (Gaussian) distributions. The mathematical formalism is verified using the recent measurements given that a generalized centrally symmetric Lévy distribution is used. The reasonable agreement is observed between estimations and experimental results for all available types of strong interaction processes and collision energies.

scholarly journals NUTRITION OF THE HOST AND NATURAL RESISTANCE TO INFECTION

1949 ◽  
Vol 89 (5) ◽  
pp. 529-539 ◽  
Author(s):  
Howard A. Schneider
Keyword(s):  
Inbred Mouse ◽  
Natural Resistance ◽  
Single Infection ◽  
Mouse Strains ◽  
Time Interval ◽  
Special Cases ◽  
Resistance To Infection ◽  
Relationship Of ◽  
First Time ◽  
The Relationship

The double strain inoculation (DSI) method of testing for natural resistance to infection has been examined in the instance of mouse salmonellosis. The DSI method has been found capable of detecting differences in natural resistance due to genetic as well as nutritional causes. A difference in response to Salmonella infection was found for the first time between the two "susceptible" inbred mouse strains, BSVR and BSVS. Whereas BSVS mice for the most part survived an intraperitoneal injection of 103 "avirulent" S. typhimurium, BSVR mice all succumbed. The relationship of the DSI test to the usual single infection test has been discussed and it is suggested that such single infection tests are special cases of the DSI test, since they involve a heterogeneous bacterial population which can be considered as a mixture of cultures of differing virulence and in which, by a single injection, the usual time interval between the two injections of the DSI method has been reduced to 0.

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