scholarly journals Opposite Effects of SiO2 Nanoparticles on the Local α and Larger-Scale α’ Segmental Relaxation Dynamics of PMMA Nanocomposites

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 979 ◽  
Author(s):  
Na Wang ◽  
Xuebang Wu ◽  
C.S. Liu
Keyword(s):  
Physical Adsorption ◽  
Sio2 Nanoparticles ◽  
Peak Height ◽  
Polymer Chains ◽  
Relaxation Dynamics ◽  
Mechanical Spectroscopy ◽  
Adsorption Effect ◽  
Nanoparticle Agglomeration ◽  
Segmental Relaxation ◽  
Opposite Behavior

The segmental relaxation dynamics of poly(methyl methacrylate)/silica (PMMA/SiO2) nanocomposites with different compositions ( ϕ SiO 2 ) near and above the glass transition temperature were investigated by mechanical spectroscopy. At ϕ SiO 2 ≤ 0.5%, the α peak temperature hardly changes with ϕ SiO 2 , but that of α’ relaxation composed of Rouse and sub-Rouse modes decreases by 15 °C due to the increase of free volume. At ϕ SiO 2 ≥ 0.7%, both α and α’ relaxations shift to high temperatures because of the steric hindrance introduced by nanoparticle agglomeration. On the other hand, with increasing ϕ SiO 2 , the peak height for α relaxation increases at ϕ SiO 2 ≤ 0.5% and then decreases at ϕ SiO 2 ≥ 0.7%, but that for α’ relaxation shows an opposite behavior. This is because at low ϕ SiO 2 , the short-chain segments related to α relaxation can easily bypass the particles, but the longer-chain segments related to α’ relaxation cannot. At high ϕ SiO 2 , the polymer chains were bound to the nanoparticles due to the physical adsorption effect, leading to the decrease of relaxation unit concentration involved in α relaxation. However, the dissociation of those bonds with heating and the concentration heterogeneity of polymer chains result in the increase of peak height for α’ relaxation.

scholarly journals Glass Transition and Interfacial Segmental Dynamics in Polymer-Particle Composites

2008 ◽  
Vol 81 (3) ◽  
pp. 506-522 ◽  
Author(s):  
C. G. Robertson ◽  
C. M. Roland
Keyword(s):  
Glass Transition ◽  
Relaxation Times ◽  
Polymer Particle ◽  
Polymer Chains ◽  
Nano Particle ◽  
Segmental Mobility ◽  
Segmental Dynamics ◽  
Reinforcing Fillers ◽  
Segmental Relaxation ◽  
Polymer Interaction

Abstract We review the literature concerned with the effect of proximity to a filler surface on the local segmental mobility of polymer chains. This mobility is commonly assessed from either the glass transition temperature, Tg, or the segmental relaxation times measured by mechanical, dielectric, or NMR spectroscopy. Published studies report increases, decreases, or no change in Tg upon the addition of carbon black, silica, and other reinforcing fillers. Similarly, the segmental relaxation times have been found to increase or be invariant to the presence of nanometer-sized particles. Some of these discrepancies can be ascribed to ambiguous methods of data analysis; others likely reflect the variation in filler-polymer interaction among different systems. There are unequivocal examples of polymers that have segmental dynamics and glass transitions unaffected by nano-particle reinforcement. However, the general principles governing the behavior remain to be clarified, with further work, focusing on the micromechanics at the particle interface, required for resolution of this important aspect of rubber science and technology.

The effect of blob size in polymer networks on nanoparticle-mediated adhesion of hydrogels

Soft Matter ◽  
2019 ◽  
Vol 15 (48) ◽  
pp. 9942-9948
Author(s):  
Sohyun Kim ◽  
Tae Hui Kang ◽  
Gi-Ra Yi
Keyword(s):  
Mesoporous Silica ◽  
Silica Nanoparticles ◽  
Pore Diameter ◽  
Physical Adsorption ◽  
Mesoporous Silica Nanoparticles ◽  
Polymer Networks ◽  
Mesh Size ◽  
Adhesion Energy ◽  
Polymer Chains

Mesoporous silica nanoparticles can be used as an adhesive for hydrogels due to their physical adsorption to polymer chains, in which adhesion energy can be affected by the ratio of mesh size and pore diameter.

scholarly journals Effect of Chitin Whiskers on the Molecular Dynamics of Carrageenan-Based Nanocomposites

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1083 ◽  
Author(s):  
Marta Carsi ◽  
Maria J. Sanchis ◽  
Clara M. Gómez ◽  
Sol Rodriguez ◽  
Fernando G. Torres
Keyword(s):  
Molecular Dynamics ◽  
Casting Process ◽  
Polymer Chains ◽  
Dielectric Relaxation Spectroscopy ◽  
Solution Casting ◽  
Fragility Index ◽  
Relaxation Dynamics ◽  
Dynamic Mobility ◽  
Chitin Nanowhiskers ◽  
Chitin Whiskers

Films of carrageenan (KC) and glycerol (g) with different contents of chitin nanowhiskers (CHW) were prepared by a solution casting process. The molecular dynamics of pure carrageenan (KC), carrageenan/glycerol (KCg) and KCg with different quantities of CHWs as a filler was studied using dielectric relaxation spectroscopy. The analysis of the CHW effect on the molecular mobility at the glass transition, Tg, indicates that non-attractive intermolecular interactions between KCg and CHW occur. The fragility index increased upon CHW incorporation, due to a reduction in the polymer chains mobility produced by the CHW confinement of the KCg network. The apparent activation energy associated with the relaxation dynamics of the chains at Tg slightly increased with the CHW content. The filler nature effect, CHW or montmorillonite (MMT), on the dynamic mobility of the composites was analyzed by comparing the dynamic behavior of both carrageenan-based composites (KCg/xCHW, KCg/xMMT).

Mechanical Relaxation Studies of Sub-Rouse Modes in Amorphous Polymers

2012 ◽  
Vol 184 ◽  
pp. 52-59 ◽  
Author(s):  
Xue Bang Wu ◽  
Hua Guang Wang ◽  
Chang Song Liu ◽  
Zhen Gang Zhu
Keyword(s):  
Relaxation Time ◽  
Coupling Model ◽  
Amorphous Polymers ◽  
Large Temperature ◽  
Mechanical Relaxation ◽  
Segmental Motion ◽  
Mechanical Spectroscopy ◽  
Segmental Dynamics ◽  
Frequency Scale ◽  
Segmental Relaxation

Mechanical spectroscopy is a powerful tool for the investigation of molecular dynamics of amorphous polymers over a large temperature range and frequency scale. In this work, by using high precision shear mechanical spectroscopy tool, we have investigated the segmental dynamics from local segmental relaxation to sub-Rouse modes in a series of amorphous polymers. We have demonstrated the existence of sub-Rouse modes slower than the local segmental motion in amorphous polymers. The sub-Rouse modes exhibit a similar change of dynamics at the same temperature TB ~1.2 Tg, as the local segmental relaxation through the temperature dependence of relaxation time and relaxation strength. Furthermore, the crossover relaxation time of the sub-Rouse modes at TB is almost the same for all the polymers investigated, i.e. τα'(TB) = 10-1±0.5 s, which is independent of molecular weight and molecular structure. This remarkable finding indicates that solely the time scale of the relaxation determines the change in dynamics of the sub-Rouse modes. According to the coupling model, the crossover is suggested to be caused by the onset of strong intermolecular cooperativity below TB. Hence the results suggest that the sub-Rouse modes and their properties are generally found in amorphous polymers by mechanical spectroscopy, and reveal the cooperative nature of the sub-Rouse modes.

scholarly journals Abstract P-34: Cryo-EM Study of Submicrocapsules with a Shell of Nanoparticle Heteroaggregates and Polyelectrolyte Layers

2021 ◽  
Vol 11 (Suppl_1) ◽  
pp. S26-S27
Author(s):  
Anastasiya Kostenko ◽  
Konstantin Palamarchuk ◽  
Yury Chesnokov ◽  
Konstantin Plokhikh ◽  
Tatyana Bukreeva ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Targeted Drug Delivery ◽  
Targeted Delivery ◽  
Colloidal Particles ◽  
Electron Tomography ◽  
Physical Adsorption ◽  
Sio2 Nanoparticles ◽  
Silicon Dioxide Nanoparticles ◽  
Liquid Form ◽  
Targeted Drug

Background: Currently, different approaches of active and passive targeted drug delivery are being developed. One of the most promising methods of targeted drug delivery is the use of capsules. For instance, colloidosomes—capsules consisting of the shell formed by colloidal particles at the interface of the emulsion—can be used for targeted delivery of antitumor drugs or any other drugs in liquid form. Here we present results of cryo-EM study of submicrocapsules with the soybean oil core and with the shell consisting of SiO2 nanoparticles and detonation nanodiamonds (DNDs) stabilized with chitosan and alginate. Methods: Сryo-electron tomography (Cryo-ET) was used to identify the morphological features of the submicrocapsules. Preliminary screening of samples and cryo-ET data collection were performed using Titan Krios cryo-EM (ThermoFisher Scientific, US) equipped with Falcon 2 direct electron detector. The restoration of the tomographic series was carried out using IMOD software. Eman2 was used for segmentation and UCSF Chimera was used for visualization of the 3D model. Submicron capsules were obtained by stabilizing oil droplets with a mixture of SiO2 nanoparticles and DNDs. To form a stable shell, an additional layer of silica particles and polyelectrolyte layers of alginate/chitosan were applied to the droplets of the dispersed phase of the emulsion by physical adsorption. Results: Cryo-EM data showed the presence of submicrocapsules with a diameter in the range of 200-900 nm. Although a significant fraction of submicrocapsules was found to be partially destroyed, results of cryo-ET study of intact capsules demonstrated that silicon dioxide nanoparticles form a net, while DNDs form clusters. Conclusion: Here we demonstrate the results of the study of submicron capsules with a shell of silica nanoparticles and DNDs. It was found that a uniform distribution of DNDs is not a prerequisite for the creation of submicron capsules that contradicts the theoretical model.

scholarly journals Experimental Investigation Of Segregation Of Carbon Atoms Due To Sub-Zero Cryogenic Treatment In Cold Work Tool Steel By Mechanical Spectroscopy And Atom Probe Tomography

2015 ◽  
Vol 60 (2) ◽  
pp. 1109-1113 ◽  
Author(s):  
N. Min ◽  
H.M. Li ◽  
CH. Xie ◽  
X.C. Wu
Keyword(s):  
Tool Steel ◽  
Atom Probe Tomography ◽  
Martensite Transformation ◽  
Cryogenic Treatment ◽  
Cold Work ◽  
Atom Probe ◽  
Peak Height ◽  
Mechanical Spectroscopy ◽  
Soaking Time ◽  
Cold Work Tool Steel

Abstract In this work, we present mechanical spectroscopy of cold work tool steel subjected to sub-zero cryogenic soaking treatment to reveal the carbon segregation and the subsequent carbides refinement. The maximum of Snoek-Köster (SK) peak height was obtained in the sample subjected to soaking 1h at −130°C cryogenic treatment. The SK peak height is reduced with prolonging the soaking time. The results indicate that an increase in the height of SK peak is connected with an increase in dislocation density and the number of segregated carbon atoms in the vicinity of dislocations or twin planes after martensite transformation at −130°C which is confirmed by corresponding TEM and atom probe tomography measurement. Hence, it is suggested that the isothermal martensite, formed during the cryogenic soaking treatment decreases (APT) the height of SK peak.

The ionic transport mechanism and coupling between the ion conduction and segmental relaxation processes of PEO20-LiCF3SO3 based ion conducting polymer clay composites

2016 ◽  
Vol 18 (29) ◽  
pp. 19955-19965 ◽  
Author(s):  
Tapabrata Dam ◽  
Sidhartha S. Jena ◽  
Dillip K. Pradhan
Keyword(s):  
Conducting Polymer ◽  
Relaxation Processes ◽  
Relaxation Dynamics ◽  
Ion Conduction ◽  
Thermally Activated ◽  
Segmental Relaxation ◽  
Ion Conducting ◽  
Ion Conduction Mechanism ◽  
Insight Into ◽  
Ion Conducting Polymer

An insight into thermally activated ion-hopping, relaxation dynamics and the coupled ion-conduction mechanism observed in ion-conducting polymer clay composites.

Single Molecule Probing of the Local Segmental Relaxation Dynamics in Polymer above the Glass Transition Temperature

2009 ◽  
Vol 131 (34) ◽  
pp. 12201-12210 ◽  
Author(s):  
Els Braeken ◽  
Gert De Cremer ◽  
Philippe Marsal ◽  
Gérard Pèpe ◽  
Klaus Müllen ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Single Molecule ◽  
Relaxation Dynamics ◽  
Segmental Relaxation

scholarly journals Nature of Carbon Black Reinforcement of Rubber: Perspective on the Original Polymer Nanocomposite

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 538
Author(s):  
Christopher G. Robertson ◽  
Ned J. Hardman
Keyword(s):  
Carbon Black ◽  
Physical Adsorption ◽  
Particle Morphology ◽  
Polymer Nanocomposite ◽  
Polymer Particle ◽  
Polymer Chains ◽  
Filled Rubber ◽  
Rubber Compounds ◽  
Filler Reinforcement ◽  
Industrial Use

Adding carbon black (CB) particles to elastomeric polymers is essential to the successful industrial use of rubber in many applications, and the mechanical reinforcing effect of CB in rubber has been studied for nearly 100 years. Despite these many decades of investigations, the origin of stiffness enhancement of elastomers from incorporating nanometer-scale CB particles is still debated. It is not universally accepted whether the interactions between polymer chains and CB surfaces are purely physical adsorption or whether some polymer–particle chemical bonds are also introduced in the process of mixing and curing the CB-filled rubber compounds. We review key experimental observations of rubber reinforced with CB, including the finding that heat treatment of CB can greatly reduce the filler reinforcement effect in rubber. The details of the particle morphology and surface chemistry are described to give insights into the nature of the CB–elastomer interfaces. This is followed by a discussion of rubber processing effects, the influence of CB on crosslinking, and various chemical modification approaches that have been employed to improve polymer–filler interactions and reinforcement. Finally, we contrast various models that have been proposed for rationalizing the CB reinforcement of elastomers.

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