scholarly journals Reversible Soft Mechanochemical Control of Biaryl Conformations through Crosslinking in a 3D Macromolecular Network

2020 ◽  
Vol 132 (51) ◽  
pp. 23483-23490
Author(s):  
Julien B. Kelber ◽  
Amina Bensalah‐Ledoux ◽  
Sarah Zahouani ◽  
Bruno Baguenard ◽  
Pierre Schaaf ◽  
...  
Keyword(s):  
Macromolecular Network

Scission and Healing in a Spinning Elastomeric Cylinder at Elevated Temperature

2002 ◽  
Vol 69 (5) ◽  
pp. 602-609 ◽  
Author(s):  
A. S. Wineman ◽  
J. A. Shaw
Keyword(s):  
Elevated Temperature ◽  
Angular Velocity ◽  
Critical Value ◽  
Anomalous Behavior ◽  
Molecular Networks ◽  
Material System ◽  
Elastomeric Material ◽  
Angular Velocities ◽  
Macromolecular Network ◽  
Temperature Responses

When an elastomeric material is subject to sufficiently high temperature, macromolecular network junctions can undergo time-dependent scission and re-crosslinking (healing). The material system then consists of molecular networks with different reference states. A constitutive framework, based on the experimental work of Tobolsky, is used to determine the evolution of deformation of a solid rubber cylinder spinning at constant angular velocity at an elevated temperature. Responses based on underlying neo-Hookean, Mooney-Rivlin, and Arruda-Boyce models, were solved numerically and compared. Different amounts of healing were studied for each case. For neo-Hookean molecular networks, there may be a critical finite time when the radius grows infinitely fast and the cylinder “blows up.” This time depends on the angular velocity and the rate of re-cross linking. In addition, no solution was possible for angular velocities above a critical value, even without the effects of scission. Such anomalous behavior does not occur for Mooney-Rivlin or Arruda-Boyce network response.

scholarly journals Multi-Step Concanavalin A Phase Separation and Early-Stage Nucleation Monitored Via Dynamic and Depolarized Light Scattering

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 620 ◽  
Author(s):  
Hévila Brognaro ◽  
Sven Falke ◽  
Celestin Nzanzu Mudogo ◽  
Christian Betzel
Keyword(s):  
Phase Separation ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Protein Interactions ◽  
Concanavalin A ◽  
Early Stage ◽  
Protein Crystallization ◽  
Cluster Formation ◽  
Macromolecular Network

Protein phase separation and protein liquid cluster formation have been observed and analysed in protein crystallization experiments and, in recent years, have been reported more frequently, especially in studies related to membraneless organelles and protein cluster formation in cells. A detailed understanding about the phase separation process preceding liquid dense cluster formation will elucidate what has, so far, been poorly understood—despite intracellular crowding and phase separation being very common processes—and will also provide more insights into the early events of in vitro protein crystallization. In this context, the phase separation and crystallization kinetics of concanavalin A were analysed in detail, which applies simultaneous dynamic light scattering and depolarized dynamic light scattering to obtain insights into metastable intermediate states between the soluble phase and the crystalline form. A multi-step mechanism was identified for ConA phase separation, according to the resultant ACF decay, acquired after an increase in the concentration of the crowding agent until a metastable ConA gel intermediate between the soluble and final crystalline phases was observed. The obtained results also revealed that ConA is trapped in a macromolecular network due to short-range intermolecular protein interactions and is unable to transform back into a non-ergodic solution.

scholarly journals CHEMO-MECHANICAL MODEL FOR PREDICTING THE LIFETIME OF EPDM RUBBERS

2019 ◽  
Vol 92 (4) ◽  
pp. 722-748 ◽  
Author(s):  
Xavier Colin ◽  
Mouna Ben Hassine ◽  
Moussa Nait-Abelaziz
Keyword(s):  
Mechanical Behavior ◽  
Thermal Aging ◽  
Mechanical Model ◽  
Degradation Kinetics ◽  
Weight Changes ◽  
Cross Link ◽  
Elementary Reactions ◽  
Industrial Material ◽  
Macromolecular Network ◽  
Concentration Changes

ABSTRACT A chemo-mechanical model has been developed for predicting the long-term mechanical behavior of EPDM rubbers in a harsh thermal oxidative environment. Schematically, this model is composed of two complementary levels: The “chemical level” calculates the degradation kinetics of the macromolecular network that is introduced into the “mechanical level” to deduce the corresponding mechanical behavior in tension. The “chemical level” is derived from a realistic mechanistic scheme composed of 19 elementary reactions describing the thermal oxidation of EPDM chains, their stabilization against oxidation by commercial antioxidants but also by sulfide bridges, and the maturation and reversion of the macromolecular network. The different rate constants and chemical yields have been determined from a heavy thermal aging campaign in air between 70 and 170 °C on four distinct EPDM formulations: additive free gum, unstabilized and stabilized sulfur vulcanized gum, and industrial material. This “chemical level” has been used as an inverse resolution method for simulating accurately the consequences of thermal aging at the molecular (concentration changes in antioxidants, carbonyl products, double bonds, and sulfide bridges), macromolecular (concentration changes in chain scissions and cross-link nodes), and macroscopic scales (weight changes). Finally, it gives access to the concentration changes in elastically active chains from which are deduced the corresponding changes in average molar mass MC between two consecutive cross-link nodes. The “mechanical level” is derived from a modified version of the statistical theory of rubber elasticity, called the phantom network theory. It relates the elastic and fracture properties to MC if considering the macromolecular network perfect, and gives access to the lifetime of the EPDM rubber based on a relevant structural or mechanical end-of-life criterion. A few examples of simulations are given to demonstrate the reliability of the chemo-mechanical model.

scholarly journals Application of Dendrimers for the Treatment of Infectious Diseases

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2205 ◽  
Author(s):  
Zandile Mhlwatika ◽  
Blessing Aderibigbe
Keyword(s):  
Drug Delivery ◽  
Drug Resistance ◽  
Infectious Diseases ◽  
Water Solubility ◽  
Three Dimensional ◽  
Parasitic Infections ◽  
Release Mechanism ◽  
Macromolecular Network ◽  
And Control ◽  
Drug Encapsulation Efficiency

Dendrimers are drug delivery systems that are characterized by a three-dimensional, star-shaped, branched macromolecular network. They possess ideal properties such as low polydispersity index, biocompatibility and good water solubility. They are made up of the interior and the exterior layers. The exterior layer consists of functional groups that are useful for conjugation of drugs and targeting moieties. The interior layer exhibits improved drug encapsulation efficiency, reduced drug toxicity, and controlled release mechanisms. These unique properties make them useful for drug delivery. Dendrimers have attracted considerable attention as drug delivery system for the treatment of infectious diseases. The treatment of infectious diseases is hampered severely by drug resistance. Several properties of dendrimers such as their ability to overcome drug resistance, toxicity and control the release mechanism of the encapsulated drugs make them ideal systems for the treatment of infectious disease. The aim of this review is to discuss the potentials of dendrimers for the treatment of viral and parasitic infections.

scholarly journals Profile of Matrix-Remodeling Proteinases in Osteoarthritis: Impact of Fibronectin

Cells ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 40 ◽  
Author(s):  
Selene Pérez-García ◽  
Mar Carrión ◽  
Irene Gutiérrez-Cañas ◽  
Raúl Villanueva-Romero ◽  
David Castro ◽  
...  
Keyword(s):  
Feedback Loop ◽  
Three Dimensional ◽  
Matrix Remodeling ◽  
Synovial Joint ◽  
Surface Receptors ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Fibronectin Fragments ◽  
Macromolecular Network ◽  
A Disintegrin And Metalloproteinase

The extracellular matrix (ECM) is a complex and specialized three-dimensional macromolecular network, present in nearly all tissues, that also interacts with cell surface receptors on joint resident cells. Changes in the composition and physical properties of the ECM lead to the development of many diseases, including osteoarthritis (OA). OA is a chronic degenerative rheumatic disease characterized by a progressive loss of synovial joint function as a consequence of the degradation of articular cartilage, also associated with alterations in the synovial membrane and subchondral bone. During OA, ECM-degrading enzymes, including urokinase-type plasminogen activator (uPA), matrix metalloproteinases (MMPs), and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs), cleave ECM components, such as fibronectin (Fn), generating fibronectin fragments (Fn-fs) with catabolic properties. In turn, Fn-fs promote activation of these proteinases, establishing a degradative and inflammatory feedback loop. Thus, the aim of this review is to update the contribution of ECM-degrading proteinases to the physiopathology of OA as well as their modulation by Fn-fs.

Coupled analysis on hyper-viscoelastic mechanical behavior and macromolecular network alteration of rubber during thermo-oxidative aging process

Polymer ◽  
2019 ◽  
Vol 171 ◽  
pp. 15-24 ◽  
Author(s):  
Jieying Zhi ◽  
Qinglin Wang ◽  
Mengjie Zhang ◽  
Zhenze Zhou ◽  
Anna Liu ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Aging Process ◽  
Coupled Analysis ◽  
Oxidative Aging ◽  
Macromolecular Network

Coal physical structure: porous rock and macromolecular network

1986 ◽  
Vol 12 ◽  
pp. 31-49 ◽  
Author(s):  
Martin L. Gorbaty ◽  
Stephen C. Mraw ◽  
Jon S. Gethner ◽  
Douglas Brenner
Keyword(s):  
Physical Structure ◽  
Porous Rock ◽  
Macromolecular Network

Investigation on the macromolecular network structure of Xianfeng lignite by a new two-step depolymerization

Fuel ◽  
2013 ◽  
Vol 109 ◽  
pp. 49-53 ◽  
Author(s):  
Chun-Xiu Pan ◽  
Xian-Yong Wei ◽  
Heng-Fu Shui ◽  
Zhi-Cai Wang ◽  
Juan Gao ◽  
...  
Keyword(s):  
Network Structure ◽  
Macromolecular Network
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