scholarly journals The Relationship between Free Volume and Cooperative Rearrangement: From the Temperature-Dependent Neutron Total Scattering Experiment of Polystyrene

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3042
Author(s):  
Zehua Han ◽  
Guisheng Jiao ◽  
Changli Ma ◽  
Taisen Zuo ◽  
Charles C. Han ◽  
...  
Keyword(s):  
Free Volume ◽  
Glass Formation ◽  
Main Chain ◽  
Real Space ◽  
Dynamics Simulation ◽  
Dynamic Heterogeneity ◽  
Temperature Dependent ◽  
Structure Variation ◽  
The Relationship ◽  
Space Image

Although many theories have been proposed to describe the nature of glass formation, its microscopic picture is still missing. Here, by a combination of neutron scattering and molecular dynamics simulation, we present the temperature-dependent atomic structure variation of polystyrene at the glass formation, free volume and cooperative rearrangement. When it is close to glass formation, the polymer is confined in tubes, whose diameter is the main chain–main chain distance, in a “static cage” from its neighbors. This definition can not only account for the kinetic pathway dependence of Williams-Landel-Ferry (WLF) free volume, but also be testified in a set of six polymers. However, the free volume which allows a monomer to move cannot be found in any frame of its real-space image. Monomers, thus, have to move cooperatively to be out of the cage. During glass formation, dynamic heterogeneity develops, and string-like cooperative rearrangement region (CRR) grows over a long range of time and length scales. All of these CRRs tend to walk through loose “static cages”. Our observation unifies the concepts of free volume and cooperative rearrangement. The former is a statistical average leading to a polydisperse “static cage” formation; while a loose “static cage” provides the way that CRRs move.

Effects of chain polarity of hindered phenol on the damping properties of polymer-based hybrid materials: insights into the molecular mechanism

2020 ◽  
Vol 40 (5) ◽  
pp. 394-402
Author(s):  
Qiaoman Hu ◽  
Junhui Wang ◽  
Kangming Xu ◽  
Hongdi Zhou ◽  
Yue Huang ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Mechanical Analysis ◽  
Dynamics Simulation ◽  
Damping Properties ◽  
Structure Variation ◽  
Hydrogen Bonding Interactions ◽  
Ft Ir ◽  
Hindered Phenol ◽  
Damping Materials ◽  
The Relationship

AbstractFor hindered phenol (HP)/polymer-based hybrid damping materials, the damping properties are greatly affected by the structure variation of HPs. However, the unclear relationship between them limits the exploitation of such promising materials. Therefore, three HPs with different chain polarity were synthesized to explore the relationship in this paper. The structures of the HPs were firstly confirmed by Nuclear Magnetic Resonance Spectrum, Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Diffraction (XRD). For further prepared HP/polyurethane hybrids, FT-IR and XRD were also adopted to confirm the hydrogen bonding interactions and micromorphologies. And, Molecular dynamics simulation was further used to characterize the effects of polarity variation on the hydrogen bonding interactions and chain packing of the hybrids in a quantitative manner. Then, combined with dynamic mechanical analysis, the relationship between the chain polarity variation of the hindered phenols and the damping properties was established.

Temperature-dependent photoluminescence from MEH-PPV and MEH-OPPV containing oxadiazole in the main chain

2006 ◽  
Vol 84 (1-2) ◽  
pp. 203-206 ◽  
Author(s):  
F. Kong ◽  
X.L. Wu ◽  
G.S. Huang ◽  
R.K. Yuan ◽  
C.Z. Yang ◽  
...  
Keyword(s):  
Main Chain ◽  
Temperature Dependent ◽  
Temperature Dependent Photoluminescence

Influence Parameters Analysis of Forming Quality and System Dynamics Simulation of Vertical Steel Bar Benting

2013 ◽  
Vol 483 ◽  
pp. 280-284
Author(s):  
Xi Jian Zheng ◽  
Xin Zhuo Wang ◽  
Jin Meng Zhang ◽  
Yu Fei Zhu
Keyword(s):  
Simulation Analysis ◽  
Reference Value ◽  
Dynamics Simulation ◽  
Forming Quality ◽  
Steel Bar ◽  
New Process ◽  
Cutting Length ◽  
Bending Radius ◽  
The Relationship

The vertical steel bar bending forming is a kind of new process of bending method. The bending speed, bending radius and clamping length H which is the parameters of vertical steel bar bending machine , is directly affect the quality of bending forming parts. This paper calculated the length of reinforcement before being incised and the springback angle of bending steel bar which obtained the reasonable cutting length and bending Angle; Then based on rigid-flexible virtual prototype technology to build the dynamics model of vertical steel bar bending system. Through simulation analysis ,it obtained the relationship between bending speed, bending radius , clamping length H and forming quality of bending steel bar. In this paper, the analysis method have reference value to the design of similar steel bar bending machines.

Variations in magnetic properties of Mexican serpentinites and related micro-textures 

2021 ◽  
Author(s):  
Sandra B. Ramírez-García ◽  
Luis M. Alva-Valdivia
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Anisotropy Of Magnetic Susceptibility ◽  
Ultramafic Rocks ◽  
Magnetic Carrier ◽  
Temperature Dependent ◽  
Geochemical Studies ◽  
The Relationship ◽  
Magnetite Formation

<p>Magnetite formation of serpentinized ultramafic rocks leads to variations in the magnetic properties of serpentinites; however, magnetite precipitation is still on debate.</p><p>In this work, we analyzed 60 cores of ultramafic rocks with a variety of serpentinization degrees. These rocks belong to the ultramafic-mafic San Juan de Otates complex in Guanajuato, Mexico. Geochemical studies have been previously conducted, enabling us to compare changes in the magnetic properties against the chemical variations generated by the serpentinization process. By studying the density and magnetic properties such as anisotropy of magnetic susceptibility, hysteresis curves as well as magnetic and temperature-dependent susceptibility and, we were able to identify the relationship between magnetic content and serpentinization degree, the predominant magnetic carrier, and to what extent the magnetite grain size depends on the serpentinization.  Variations in these parameters allowed us to better constrain the temperature at which serpentinization occurred, the generation of other Fe-rich phases such as Fe-brucite and/or Fe-rich serpentine as well as distinctive rock textures formed at different serpentinization degrees.</p>

scholarly journals Molecule Dynamics Simulation of the Effect of Oxidative Aging on Properties of Nitrile Rubber

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 226
Author(s):  
Jinsong Yang ◽  
Weitao Lou
Keyword(s):  
Free Volume ◽  
Dynamic Properties ◽  
Compressive Strain ◽  
Mean Square Displacement ◽  
Nitrile Rubber ◽  
Dynamics Simulation ◽  
Hydroxyl Groups ◽  
Carbonyl Groups ◽  
Fractional Free Volume ◽  
Oxidative Aging

The effects of oxidative aging on the static and dynamic properties of nitrile rubber at the molecular scale were investigated by molecular dynamics simulation. The aged nitrile rubber models were constructed by introducing hydroxyl groups and carbonyl groups into rubber molecular chains to mimic oxidative aging. The static and dynamic properties of the unaged and aged nitrile rubber under different conditions were evaluated by mean square displacement, self-diffusion coefficients, hydrogen bond, fractional free volume, radial distribution function, cohesive energy density and solubility parameter. The results show that the elevated temperature intensified significantly the mobility of rubber molecular chains and fractional free volume, while the compressive strain displayed the opposite effect resulting in packing and rearrangement of rubber chains. The introduction of hydroxyl groups and carbonyl groups enhanced the polarity, intermolecular interactions, the volume and rigidity of molecular chains, implying weaker mobility of molecular chains as compared to unaged models. The compressive strain and oxidative aging both decreased the fractional free volume, which inhibited gaseous and liquid diffusion into the rubber materials, and slowed down the oxidative aging rate. This study provides insights to better understand the effect of molecular changes due to oxidative aging on the structural and dynamic properties of rubber materials at the molecular level.

scholarly journals Attachment of Paramecium to polystyrene surfaces: a model system for the analysis of sexual cell recognition and nuclear activation

1982 ◽  
Vol 58 (1) ◽  
pp. 185-199
Author(s):  
A. Kitamura
Keyword(s):  
Temperature Dependent ◽  
Polystyrene Surface ◽  
Nuclear Activation ◽  
Attachment Sites ◽  
Hydrophilic Nature ◽  
Ca Ions ◽  
Sexual Recognition ◽  
Conjugation Process ◽  
The Relationship ◽  
I Cells

In the ciliate Paramecium caudatum, only mating-reactive cells can attach to the polystyrene surface of Petri dishes. The attachment of mating-reactive cells occurs exclusively at the tips of ventrally located cilia (mating-reactive cilia) and appears to involve a hydrophobic interaction. An increase in the hydrophilic nature of the polystyrene surface following treatment with sulphuric acid results in the loss of attachment of reactive cells. The presence or absence of Ca ions and varying the ionic strength of the medium have no effect upon attachment. Although attachment reactivity is closely correlated with mating reactivity, the attachment sites appear distinct from the mating recognition sites, as suggested by the following experimental results: (I) cells that lose mating reactivity following treatment with trypsin are still able to attach to the polystyrene surface; (2) the attachment of cells appears temperature-dependent over a range where mating reactivity remains uneffected; (3) mating reactivity is quickly lost as a result of attachment to the surface of the dish. While the mechanism of attachment is not the same as sexual recognition, the attachment to the polystyrene surface initiates the early stages of the conjugation process. Cells that attach show micronuclear migration while unattached cells do not. The maximum rate of micronuclear migration occurs approximately 30 min after attachment. Meiosis does not occur following migration in the attached cells as in cells that are sexually mating. The relationship between the mating substance and the attachment substance is discussed, while the utilization of the attachment phenomenon for other experimental procedures is proposed.

scholarly journals The influence of temperature on methane adsorption in coal: A review and statistical analysis

2019 ◽  
Vol 37 (9-10) ◽  
pp. 745-763 ◽  
Author(s):  
Zhijun Wang ◽  
Xiaojuan Wang ◽  
Weiqin Zuo ◽  
Xiaotong Ma ◽  
Ning Li
Keyword(s):  
Coalbed Methane ◽  
Methane Adsorption ◽  
Gas Content ◽  
Future Research ◽  
Temperature Dependent ◽  
Current State ◽  
Influence Of Temperature On ◽  
State Of Research ◽  
Increasing Temperature ◽  
The Relationship

The capacity of coal to adsorb methane is greatly affected by temperature and, in recent years, temperature-dependent adsorption has been studied by many researchers. Even so, comprehensive conclusions have not been reached and conflicting experimental results are common. This paper reviews the current state of research regarding the temperature-dependent adsorption of methane in coal and catalogs the conclusions from experiments conducted on that subject by 28 researchers, as published between 1995 and 2017. Probability theory and statistics are used to show that the conclusion generally accepted by most researchers is that the amount of methane adsorbed by coal decreases with increasing temperature. It is highly likely that the Langmuir volume decreases as the temperature rises, and it is also probable that the Langmuir pressure increases at higher temperatures. Equations are presented that express the relationships between methane adsorption, Langmuir volume, Langmuir pressure, and temperature. Future research should be directed toward determining the relationship between Langmuir pressure and temperature. The results of the study presented herein provide a theoretical basis for predicting the gas content in coal seams and improving the efficiency of coalbed methane development.

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