scholarly journals Confinement in Extruded Nanocomposites Based on PCL and Mesoporous Silicas: Effect of Pore Sizes and Their Influence in Ultimate Mechanical Response

2021 ◽  
Vol 5 (12) ◽  
pp. 321
Author(s):  
Tamara M. Díez-Rodríguez ◽  
Enrique Blázquez-Blázquez ◽  
Nadine L. C. Antunes ◽  
Maria do Rosário Ribeiro ◽  
Ernesto Pérez ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Variable Temperature ◽  
Morphological Characteristics ◽  
Structural Features ◽  
Mesoporous Silicas ◽  
Accurate Information ◽  
Pore Sizes ◽  
X Ray Scattering ◽  
Lower Temperature ◽  
Mcm 41

In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas, MCM-41 and SBA-15, were attained by melt extrusion. The effect of the silica incorporated within the PCL matrix was observed, firstly, in the morphological characteristics and degradation behavior of the resultant composites. DSC experiments provided information on the existence of confinement in the PCL–SBA-15 materials through the appearance of an additional small endotherm, located at about 25–50 °C, and attributed to the melting of constrained crystallites. Displacement to a slightly lower temperature of this endothermic event was observed in the first heating run of PCL–MCM-41 composites, attributed to the inferior pore size in the MCM-41 particles. Thus, this indicates variations in the inclusion of PCL chains within these two mesostructures with different pore sizes. Real-time variable-temperature small-angle X-ray scattering (SAXS) experiments with synchrotron radiation were crucial to confirm the presence of PCL within MCM-41 and SBA-15 pores. Accurate information was also deduced from these measurements regarding the influence of these two mesoporous MCM-41 and SBA-15 silicas on PCL long spacing. The differences found in these morphological and structural features were responsible for the ultimate mechanical response exhibited by the two sets of PCL nanocomposites, with a considerably higher increase of mechanical parameters in the SBA-15 family.

scholarly journals Nanocomposites of PCL and SBA-15 Particles Prepared by Extrusion: Structural Characteristics, Confinement of PCL Chains within SBA-15 Nanometric Channels and Mechanical Behavior

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 129
Author(s):  
Tamara M. Díez-Rodríguez ◽  
Enrique Blázquez-Blázquez ◽  
Nadine L. C. Antunes ◽  
Maria Do Rosario Gomes Ribeiro ◽  
Ernesto Pérez ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Variable Temperature ◽  
Structural Characteristics ◽  
Structural Features ◽  
Wide Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Polymeric Chains ◽  
Mesoporous Particles

A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 silica that were prepared by melt extrusion was carried out by analyzing the possible effect of this filler on the crystalline details of PCL, on its mechanical behavior, and on the eventual observation of the confinement of the polymeric chains within the hollow nanometric silica channels. Thus, simultaneous Small-Angle and Wide-Angle X-ray Scattering (SAXS/WAXS) synchrotron experiments at variable temperature were performed on these PCL nanocomposites with different mesoporous silica contents. The importance of the morphological and structural features was assessed by the changes that were observed during the mechanical response of the final materials, which determined that the presence of mesoporous particles leads to a noticeable reinforcing effect.

scholarly journals Variation of Ultimate Properties in Extruded iPP-Mesoporous Silica Nanocomposites by Effect of iPP Confinement within the Mesostructures

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 70
Author(s):  
Rosa Barranco-García ◽  
José M. Gómez-Elvira ◽  
Jorge A. Ressia ◽  
Lidia Quinzani ◽  
Enrique M. Vallés ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Variable Temperature ◽  
Time Variable ◽  
Degradation Behavior ◽  
Precise Information ◽  
X Ray ◽  
Silica Nanocomposites ◽  
X Ray Scattering ◽  
Ultimate Properties ◽  
Mcm 41

Nanocomposites based on isotactic polypropylene (iPP) and mesoporous silica particles of either MCM-41 or SBA-15 were prepared by melt extrusion. The effect of the silica incorporated into an iPP matrix was firstly detected in the degradation behavior and in the rheological response of the resultant composites. Both were ascribed, in principle, to variations in the inclusion of iPP chains within these two mesostructures, with well different pore size. DSC experiments did not provide information on the existence of confinement in the iPP-MCM-41 materials, whereas a small endotherm, located at about 100 °C and attributed to the melting of confined crystallites, is clearly observed in the iPP-SBA-15 composites. Real-time variable-temperature Small Angle X-ray Scattering (SAXS) experiments with synchrotron radiation turned out to be crucial to finding the presence of iPP within MCM-41 pores. From these measurements, precise information was also deduced on the influence of the MCM-41 on iPP long spacing since overlapping does not occur between most probable iPP long spacing peak with the characteristic diffractions from the MCM-41 hexagonal nanostructure in comparison with existing superposition in SBA-15-based materials.

The Effect of Uniaxial Cyclic Deformation on the Evolution of Phase Transformation Fronts in Pseudoelastic NiTi Wire

2001 ◽  
Author(s):  
Mark A. Iadicola ◽  
John A. Shaw
Keyword(s):  
Mechanical Response ◽  
Infrared Imaging ◽  
Partial Transformation ◽  
Niti Wire ◽  
Full Field ◽  
Temperature Experiment ◽  
Background Temperature ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Niti Wires

Abstract Experiments are presented of the response of pseudoelastic NiTi wires subjected to displacement controlled cycles. A custom built thermo-mechanical testing apparatus is used to control the background temperature field of the wire specimen while allowing the evolution of transformation fronts to be tracked by full field infrared imaging. Two experiments under similar end-displacement histories, but at temperatures ≈8°C apart, are shown to give remarkably different cyclic responses. The mechanical response for the lower temperature experiment continued to soften but retained its shape through 43 partial transformation cycles, and the pattern of transformation fronts seemed to reach a steady state. The response for the higher temperature experiment showed a change in shape of the mechanical response and distinct changes in transformation front patterns over 31 partial transformation cycles.

scholarly journals Calculation of Differential Propagation Constant Determined by Plant Morphology Using Polarimetric Measurement

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Chufeng Hu ◽  
Nanjing Li
Keyword(s):  
Electromagnetic Wave ◽  
Measurement System ◽  
Random Distribution ◽  
Propagation Constant ◽  
Morphological Characteristics ◽  
Plant Morphology ◽  
Structural Features ◽  
Low Frequencies ◽  
Mathematical Relation ◽  
Power Profile

The morphology of vegetation greatly impacts propagation of polarized electromagnetic wave. In order to validate this phenomenon, the mathematical relation between the differential propagation constant of forest vegetation and of its polarized echo is quantitatively derived by using backscattering power profile. The fluctuation of differential propagation constant with frequency is analyzed by combining the morphological characteristics of vegetation. The accurate copolarized data of 3–10 GHz frequency-domain of small trees are obtained by indoor wideband polarimetric measurement system. The results show that morphological characteristics of vegetation at different frequencies can be obtained by the differential propagation constant of polarized electromagnetic wave. At low frequencies, the plants with structural features presented oriented distribution. However, the plants show random distribution of the echoes at higher frequencies, which is mainly from the canopy. The research provides important information to choose the coherence models employed in the parameters retrieval of vegetations.

Alkylation of phenol with tert-butyl alcohol catalyzed by ionic liquid-supported MCM-41 with different pore sizes

2018 ◽  
Vol 125 (1) ◽  
pp. 351-364 ◽  
Author(s):  
Tingshun Jiang ◽  
Yingjie Xie ◽  
Liming Dai ◽  
Yingying Li ◽  
Qian Zhao
Keyword(s):  
Ionic Liquid ◽  
Butyl Alcohol ◽  
Tert Butyl ◽  
Pore Sizes ◽  
Tert Butyl Alcohol ◽  
Mcm 41

scholarly journals Structural characterization of the N-terminal part of the MERS-CoV nucleocapsid by X-ray diffraction and small-angle X-ray scattering

2016 ◽  
Vol 72 (2) ◽  
pp. 192-202 ◽  
Author(s):  
Nicolas Papageorgiou ◽  
Julie Lichière ◽  
Amal Baklouti ◽  
François Ferron ◽  
Marion Sévajol ◽  
...  
Keyword(s):  
Structural Model ◽  
Structural Features ◽  
Terminal Region ◽  
X Ray Diffraction ◽  
Terminal Part ◽  
Multifunctional Protein ◽  
X Ray ◽  
N Protein ◽  
Intrinsically Disordered ◽  
X Ray Scattering

The N protein of coronaviruses is a multifunctional protein that is organized into several domains. The N-terminal part is composed of an intrinsically disordered region (IDR) followed by a structured domain called the N-terminal domain (NTD). In this study, the structure determination of the N-terminal region of the MERS-CoV N proteinviaX-ray diffraction measurements is reported at a resolution of 2.4 Å. Since the first 30 amino acids were not resolved by X-ray diffraction, the structural study was completed by a SAXS experiment to propose a structural model including the IDR. This model presents the N-terminal region of the MERS-CoV as a monomer that displays structural features in common with other coronavirus NTDs.

scholarly journals Functionalized Ordered Mesoporous Silicas (MCM-41): Synthesis and Applications in Catalysis

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 617 ◽  
Author(s):  
Gabriel Martínez-Edo ◽  
Alba Balmori ◽  
Iris Pontón ◽  
Andrea Martí del Rio ◽  
David Sánchez-García
Keyword(s):  
Mesoporous Silica ◽  
Pore Structure ◽  
Metallic Nanoparticles ◽  
Mesoporous Silicas ◽  
Acid Catalysts ◽  
Catalytic Systems ◽  
Research Attention ◽  
Ordered Mesoporous ◽  
Regioselective Functionalization ◽  
Mcm 41

Mesoporous silica sieves are among the most studied nano-objects due to their stable pore structure and easy preparation. In particular, MCM-41 have attracted increasing research attention due to their chemical versatility. This review focuses on the synthesis and regioselective functionalization of MCM-41 to prepare catalytic systems. The topics covered are: mono and di-functionalized MCM-41 as basic and acid catalysts, catalysts based on metallic complexes and heteropolyacids supported onto MCM-41, metallic nanoparticles embed onto functionalized MCM-41 and magnetic MCM-41 for catalytic purposes.

Characterizing nanoparticles with a laboratory diffractometer: from small-angle to total X-ray scattering

2014 ◽  
Vol 29 (S1) ◽  
pp. S47-S53 ◽  
Author(s):  
Marco Sommariva ◽  
Milen Gateshki ◽  
Jan-André Gertenbach ◽  
Joerg Bolze ◽  
Uwe König ◽  
...  
Keyword(s):  
Small Angle ◽  
Structural Features ◽  
Bragg Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Pdf Analysis ◽  
Comprehensive Picture ◽  
Ray Scattering

X-ray diffraction and scattering on a single multipurpose X-ray platform have been used to probe the structure, composition, and thermal behavior of TiO2 nanoparticles ranging in size from 1 to 10 nm. Ambient and non-ambient Bragg diffraction, small-angle X-ray scattering (SAXS), as well as total scattering and pair-distribution function (PDF) analysis are combined to obtain a comprehensive picture of the samples. At these ultrasmall particle-size dimensions, SAXS and PDF prove powerful in distinguishing the salient features of the materials, in particular the size distribution of the primary particles (SAXS) and the identification of the TiO2 polymorphs (PDF). Structural features determined by X-ray scattering techniques are corroborated by high-resolution transmission electron microscopy. The elemental make-up of the materials has been measured using X-ray fluorescence spectrometry and energy-dispersive X-ray analysis.

scholarly journals Isolation of infectious, non-fibrillar and oligomeric prions from a genetic prion disease

Brain ◽  
2020 ◽  
Vol 143 (5) ◽  
pp. 1512-1524 ◽  
Author(s):  
Ilaria Vanni ◽  
Laura Pirisinu ◽  
Claudia Acevedo-Morantes ◽  
Razieh Kamali-Jamil ◽  
Vineet Rathod ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Amyloid Fibrils ◽  
Morphological Characteristics ◽  
Immunogold Labelling ◽  
Structural Features ◽  
Cellular Prion Protein ◽  
Proteinase K ◽  
Supernatant Fraction ◽  
C Terminus ◽  
Electron Microscopy Analysis

Abstract Prions are transmissible agents causing lethal neurodegenerative diseases that are composed of aggregates of misfolded cellular prion protein (PrPSc). Despite non-fibrillar oligomers having been proposed as the most infectious prion particles, prions purified from diseased brains usually consist of large and fibrillar PrPSc aggregates, whose protease-resistant core (PrPres) encompasses the whole C-terminus of PrP. In contrast, PrPSc from Gerstmann-Sträussler-Scheinker disease associated with alanine to valine substitution at position 117 (GSS-A117V) is characterized by a small protease-resistant core, which is devoid of the C-terminus. We thus aimed to investigate the role of this unusual PrPSc in terms of infectivity, strain characteristics, and structural features. We found, by titration in bank voles, that the infectivity of GSS-A117V is extremely high (109.3 ID50 U/g) and is resistant to treatment with proteinase K (109.0 ID50 U/g). We then purified the proteinase K-resistant GSS-A117V prions and determined the amount of infectivity and PrPres in the different fractions, alongside the morphological characteristics of purified PrPres aggregates by electron microscopy. Purified pellet fractions from GSS-A117V contained the expected N- and C-terminally cleaved 7 kDa PrPres, although the yield of PrPres was low. We found that this low yield depended on the low density/small size of GSS-A117V PrPres, as it was mainly retained in the last supernatant fraction. All fractions were highly infectious, thus confirming the infectious nature of the 7 kDa PrPres, with infectivity levels that directly correlated with the PrPres amount detected. Finally, electron microscopy analysis of these fractions showed no presence of amyloid fibrils, but only very small and indistinct, non-fibrillar PrPresparticles were detected and confirmed to contain PrP via immunogold labelling. Our study demonstrates that purified aggregates of 7 kDa PrPres, spanning residues ∼90–150, are highly infectious oligomers that encode the biochemical and biological strain features of the original sample. Overall, the autocatalytic behaviour of the prion oligomers reveals their role in the propagation of neurodegeneration in patients with Gerstmann-Sträussler-Scheinker disease and implies that the C-terminus of PrPSc is dispensable for infectivity and strain features for this prion strain, uncovering the central PrP domain as the minimal molecular component able to encode infectious prions. These findings are consistent with the hypothesis that non-fibrillar prion particles are highly efficient propagators of disease and provide new molecular and morphological constraints on the structure of infectious prions.

scholarly journals Synchrotron and Raman Study of the Rotator Phases and Polymorphism in Tricosane Paraffin

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1341
Author(s):  
Enrique Blázquez-Blázquez ◽  
Rosa Barranco-García ◽  
María L. Cerrada ◽  
Juan C. Martínez ◽  
Ernesto Pérez
Keyword(s):  
Phase Behavior ◽  
Variable Temperature ◽  
Low Frequency ◽  
Frequency Region ◽  
Time Variable ◽  
Wide Angle ◽  
Multistage Model ◽  
X Ray ◽  
X Ray Scattering ◽  
Raman Study

A detailed study of the phase behavior of n-paraffin C23H48 has been performed by means of real-time variable-temperature experiments with synchrotron radiation. Two detectors were employed for simultaneous analysis of the small-angle (SAXS) and wide-angle X-ray-scattering (WAXS) regions. This paraffin presents a very interesting phase behavior, involving two crystal polymorphs, three rotator phases and the liquid state. The Ostwald rule of stages is invoked to find similarities of the rotator phases with the eventual transient mesomorphic structure in the multistage model of polymer crystallization. That study is complemented by variable-temperature Raman experiments covering frequencies down to 150 cm−1. It was found that the low-frequency region is the most informative regarding the phase transitions, and specifically the intensity of the first overtone. From these analyses, several parameters are evaluated as function of temperature.

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