scholarly journals Mechanical Response of Two-Dimensional Polymer Networks: Role of Topology, Rate Dependence, and Damage Accumulation

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Konik Kothari ◽  
Yuhang Hu ◽  
Sahil Gupta ◽  
Ahmed Elbanna
Keyword(s):  
Mechanical Response ◽  
Polymer Networks ◽  
Soft Materials ◽  
Crosslinking Density ◽  
State Theory ◽  
Polymer Chains ◽  
Local Network ◽  
Network Characteristics ◽  
Rate Dependent

The skeleton of many natural and artificial soft materials can be abstracted as networks of fibers/polymers interacting in a nonlinear fashion. Here, we present a numerical model for networks of nonlinear, elastic polymer chains with rate-dependent crosslinkers similar to what is found in gels. The model combines the worm-like chain (WLC) at the polymer level with the transition state theory for crosslinker bond dynamics. We study the damage evolution and the force—displacement response of these networks under uniaxial stretching for different loading rates, network topology, and crosslinking density. Our results suggest a complex nonmonotonic response as the loading rate or the crosslinking density increases. We discuss this in terms of the microscopic deformation mechanisms and suggest a novel framework for increasing toughness and ductility of polymer networks using a bio-inspired sacrificial bonds and hidden length (SBHL) mechanism. This work highlights the role of local network characteristics on macroscopic mechanical observables and opens new pathways for designing tough polymer networks.

Modeling fracture in rate-dependent polymer networks: A quasicontinuum approach

2021 ◽  
pp. 1-22
Author(s):  
Ahmed Ghareeb ◽  
Ahmed Elbanna
Keyword(s):  
Adaptive Mesh Refinement ◽  
Polymer Networks ◽  
Viscoelastic Behavior ◽  
Adaptive Mesh ◽  
Soft Materials ◽  
Polymer Chains ◽  
Loading Rates ◽  
Viscous Forces ◽  
Rate Dependent ◽  
Bond Breakage

Abstract Soft materials, such as rubber and gels, exhibit rate-dependent response where the stiffness, strength and fracture patterns depend largely on loading rates. Thus, accurate modeling of the mechanical behavior requires accounting for different sources of rate-dependence such as the intrinsic viscoelastic behavior of the polymer chains and the dynamic bond breakage and formation mechanism. In this chapter, we extend the QC approach presented in Ghareeb and Elbanna [Journal of the Mechanics and Physics of Solids, 137, 103819 (2020)] to include ratedependent behavior of polymer networks. We propose a homogenization rule for the viscous forces in the polymer chains and update the adaptive mesh refinement algorithm to account for dynamic bond breakage. Then, we use nonlinear finite element framework with predictorcorrector scheme to solve for the nodal displacements and velocities. We demonstrate the accuracy of the method by verifying it against fully discrete simulations for different examples of network structures and loading conditions. We further use the method to investigate the effects of the loading rates on the fracture characteristics of networks with different ratedependent parameters. Finally, We discuss the implications of the extended method for multiscale analysis of fracture in rate-dependent polymer networks.

scholarly journals A finite dissipative theory of temporary interfibrillar bridges in the extracellular matrix of ligaments and tendons

2008 ◽  
Vol 6 (39) ◽  
pp. 909-924 ◽  
Author(s):  
P. Ciarletta ◽  
M. Ben Amar
Keyword(s):  
Extracellular Matrix ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Collagen Type I ◽  
State Theory ◽  
Ground Substance ◽  
Type I ◽  
Dissipative Effects ◽  
Rate Dependent

The structural integrity and the biomechanical characteristics of ligaments and tendons result from the interactions between collagenous and non-collagenous proteins (e.g. proteoglycans, PGs) in the extracellular matrix. In this paper, a dissipative theory of temporary interfibrillar bridges in the anisotropic network of collagen type I, embedded in a ground substance, is derived. The glycosaminoglycan chains of decorin are assumed to mediate interactions between fibrils, behaving as viscous structures that transmit deformations outside the collagen molecules. This approach takes into account the dissipative effects of the unfolding preceding fibrillar elongation, together with the slippage of entire fibrils and the strain-rate-dependent damage evolution of the interfibrillar bridges. Thermodynamic consistency is used to derive the constitutive equations, and the transition state theory is applied to model the rearranging properties of the interfibrillar bridges. The constitutive theory is applied to reproduce the hysteretic spectrum of the tissues, demonstrating how PGs determine damage evolution, softening and non-recoverable strains in their cyclic mechanical response. The theoretical predictions are compared with the experimental response of ligaments and tendons from referenced studies. The relevance of the proposed model in mechanobiology research is discussed, together with several applications from medical practice to bioengineering science.

Thermodynamics and Stereochemistry of Diels–Alder Polymer Networks: Role of Crosslinker Flexibility and Crosslinking Density

2021 ◽  
Author(s):  
Qing Zhou ◽  
Zhen Sang ◽  
Kartik Kumar Rajagopalan ◽  
Yelena Sliozberg ◽  
Frank Gardea ◽  
...  
Keyword(s):  
Polymer Networks ◽  
Crosslinking Density ◽  
Diels Alder

scholarly journals Crosslinker-Based Regulation of Swelling Behavior of Poly(N-isopropylacrylamide) Gels in a Post-Polymerization Crosslinking System

Gels ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Shohei Ida ◽  
Akimitsu Katsurada ◽  
Mitsuhiro Tsujio ◽  
Motoharu Nakamura ◽  
Yoshitsugu Hirokawa
Keyword(s):  
Solvent Effect ◽  
Structural Diversity ◽  
Soft Materials ◽  
Polymer Gels ◽  
Crosslinking Density ◽  
Swelling Behavior ◽  
Polymer Chains ◽  
Gel Properties ◽  
Alkyl Chains ◽  
Fundamental Understanding

A fundamental understanding of the effect of a crosslinker on gel properties is important for the design of novel soft materials because a crosslinking is a key component of polymer gels. We focused on post-polymerization crosslinking (PPC) system utilizing activated ester chemistry, which is a powerful tool due to structural diversity of diamine crosslinkers and less susceptibility to solvent effect compared to conventional divinyl crosslinking system, to systematically evaluate the crosslinker effect on the gel properties. A variety of alkyldiamine crosslinkers was employed for the synthesis of poly(N-isopropylacrylamide) (PNIPAAm) gels and it was clarified that the length of alkyl chains of diamine crosslinkers strongly affected the gelation reaction and the swelling behavior. The longer crosslinker induced faster gelation and decreased the swelling degree and the response temperature in water, while the crosslinking density did not significantly change. In addition, we were able to modify the polymer chains in parallel with crosslinking by using a monoamine modifier along with a diamine crosslinker. This simultaneous chain modification during crosslinking (SMC) was demonstrated to be useful for the regulation of the crosslinking density and the swelling behavior of PNIPAAm gels.

Platelet and Shear Rate Promote Tumor Cell Adhesion to Human Endothelial Extracellular Matrix - Absence of a Role for Platelet Cyclooxygenase

1989 ◽  
Vol 61 (03) ◽  
pp. 485-489 ◽  
Author(s):  
Eva Bastida ◽  
Lourdes Almirall ◽  
Antonio Ordinas
Keyword(s):  
Cell Adhesion ◽  
Shear Rate ◽  
Tumor Cell ◽  
Umbilical Vein ◽  
Blood Platelets ◽  
Flow Conditions ◽  
Tumor Cell Adhesion ◽  
Rate Dependent ◽  
Static Conditions

SummaryBlood platelets are thought to be involved in certain aspects of malignant dissemination. To study the role of platelets in tumor cell adherence to vascular endothelium we performed studies under static and flow conditions, measuring tumor cell adhesion in the absence or presence of platelets. We used highly metastatic human adenocarcinoma cells of the lung, cultured human umbilical vein endothelial cells (ECs) and extracellular matrices (ECM) prepared from confluent EC monolayers. Our results indicated that under static conditions platelets do not significantly increase tumor cell adhesion to either intact ECs or to exposed ECM. Conversely, the studies performed under flow conditions using the flat chamber perfusion system indicated that the presence of 2 × 105 pl/μl in the perfusate significantly increased the number of tumor cells adhered to ECM, and that this effect was shear rate dependent. The maximal values of tumor cell adhesion were obtained, in presence of platelets, at a shear rate of 1,300 sec-1. Furthermore, our results with ASA-treated platelets suggest that the role of platelets in enhancing tumor cell adhesion to ECM is independent of the activation of the platelet cyclooxygenase pathway.

Exploring secondary interactions and the role of temperature in moisture-contaminated polymer networks through molecular simulations

Soft Matter ◽  
2021 ◽  
Vol 17 (10) ◽  
pp. 2942-2956
Author(s):  
Rishabh D. Guha ◽  
Ogheneovo Idolor ◽  
Katherine Berkowitz ◽  
Melissa Pasquinelli ◽  
Landon R. Grace
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Temperature Variation ◽  
Polymer Networks ◽  
Molecular Simulations ◽  
Effect Of Temperature ◽  
Secondary Interactions ◽  
Dynamics Simulations ◽  
Secondary Bonding

We investigated the effect of temperature variation on the secondary bonding interactions between absorbed moisture and epoxies with different morphologies using molecular dynamics simulations.

The Role of Mechanical Tension in Neurons

2010 ◽  
Vol 1274 ◽  
Author(s):  
Taher Saif ◽  
Jagannathan Rajagopalan ◽  
Alireza Tofangchi
Keyword(s):  
Mechanical Response ◽  
Mechanical Forces ◽  
Active Tension ◽  
Mechanical Tension ◽  
Deformation Response ◽  
Linear Force ◽  
Tension Regulation ◽  
Over Time

AbstractWe used high resolution micromechanical force sensors to study the in vivo mechanical response of embryonic Drosophila neurons. Our experiments show that Drosophila axons have a rest tension of a few nN and respond to mechanical forces in a manner characteristic of viscoelastic solids. In response to fast externally applied stretch they show a linear force-deformation response and when the applied stretch is held constant the force in the axons relaxes to a steady state value over time. More importantly, when the tension in the axons is suddenly reduced by releasing the external force the neurons actively restore the tension, sometimes close to their resting value. Along with the recent findings of Siechen et al (Proc. Natl. Acad. Sci. USA 106, 12611 (2009)) showing a link between mechanical tension and synaptic plasticity, our observation of active tension regulation in neurons suggest an important role for mechanical forces in the functioning of neurons in vivo.

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