Relaxation Behavior In Molecular Dynamics Simulations Of Simple Polymers
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Relaxation Behavior In Molecular Dynamics Simulations Of Simple Polymers
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Author : Taylor Dotson
language : en
Publisher:
Release Date : 2008
Relaxation Behavior In Molecular Dynamics Simulations Of Simple Polymers written by Taylor Dotson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Mathematical models categories.
Viscoelastic materials exhibit complex stress-strain behavior with respect to time, temperature and magnitude. Study of viscoelastic behavior by physical experimentation is very much limited by the cost and current capabilities of rheological equipment. Additionally, macroscopic relaxations often occur at time-scales that are impractical to study experimentally. For this reason, computer molecular dynamic simulations are becoming increasingly popular in this field of study. Mechanical behavior on the molecular level can be studied through the use of autocorrelation functions with the intention of using them to eventually predict the macroscopic stress relaxation modulus of the given material. However, the inversion of such functions into a useful model tends to be a very ill-posed problem and many widely used inversion methods do not adequately address this ill-posedness. Mechanical relaxation is explored on a microscopic level through the use of autocorrelation functions for several simple bead-spring models of short polymer chains. Specically, the end-to-end and dihedral angle correlation functions are analyzed. The parameters are found to collapse to single-valued functions for the freely jointed and freely rotating models.
Polymer Dynamics And Relaxation
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Author : Richard Boyd
language : en
Publisher: Cambridge University Press
Release Date : 2010-08-05
Polymer Dynamics And Relaxation written by Richard Boyd and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-08-05 with Technology & Engineering categories.
Polymers exhibit a range of physical characteristics, from rubber-like elasticity to the glassy state. These particular properties are controlled at the molecular level by the mobility of the structural constituents. Remarkable changes in mobility can be witnessed with temperature, over narrow, well defined regions, termed relaxation processes. This is an important, unique phenomenon controlling polymer transition behaviour and is described here at an introductory level. The important types of relaxation processes from amorphous to crystalline polymers and polymeric miscible blends are covered, in conjunction with the broad spectrum of experimental methods used to study them. In-depth discussion of molecular level interpretation, including atomistic level computer simulations and applications to molecular mechanism elucidation, are discussed. The result is a self-contained approach to polymeric interpretation suitable for researchers in materials science, physics and chemistry interested in the relaxation processes of polymeric systems.
Relaxation In Physical And Mechanical Behavior Of Polymers
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Author : Maxim Arzhakov
language : en
Publisher: CRC Press
Release Date : 2019-01-30
Relaxation In Physical And Mechanical Behavior Of Polymers written by Maxim Arzhakov and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-01-30 with Science categories.
Explores the nature of relaxation phenomena in polymers on the basis of time-temperature equivalence. Its role in the physical and mechanical behavior of polymers materials and fundamentals of thermoplastics processing are discussed. Four appendixes detail thermo-mechanical methods to study relaxation in polymers, structure of both amorphous and semi-crystalline polymers, and unified approach to describe deformation of polymeric materials.
Polymer Viscoelasticity
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Author : Y.-H. Lin
language : en
Publisher: World Scientific
Release Date : 2011
Polymer Viscoelasticity written by Y.-H. Lin and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Science categories.
This book covers in great detail the Rouse-segment-based molecular theories in polymer viscoelasticity ? the Rouse theory and the extended reptation theory (based on the framework of the Doi?Edwards theory) ? that have been shown to explain experimental results in a consistently quantitative way. The explanation for the 3.4 power law of viscosity, quantitative line-shape analyses of viscoelastic responses and agreements between different sorts of viscoelastic responses, the consistency between the viscoelasticity and diffusion results, the clarification of the onset of entangelement, the discovery of the number of entanglement strands per cubed entanglement distance being a universal constant and the basic mechanism of the glass transition-related thermorheological complexity are discussed or shown in great detail. The mystery behind the success of the Rouse-segment-based molecular theories over the entropic region of a viscoelastic response is revealed by the Monte Carlo simulations on the Fraenkel chains. Specifically, the simulation studies give a natural explanation for the coexistence of the energy-driven and entropy-driven modes in a viscoelastic response and provide a theoretical basis resolving the paradox that the experimentally determined sizes of Rouse and Kuhn segments are nearly the same. This book starts from a very fundamental level; each chapter is built upon the contents of the previous chapters. Thus, the readers may use the book as a textbook and eventually reach an advanced research level. This book is also a useful source of reference for physicists, chemists and material scientists.
Polymer Dynamics And Relaxation
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Author : Richard Hays Boyd
language : en
Publisher:
Release Date : 2007
Polymer Dynamics And Relaxation written by Richard Hays Boyd and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Electronic book categories.
This book was first published in 2007. Polymers exhibit a range of physical characteristics, from rubber-like elasticity to the glassy state. These particular properties are controlled at the molecular level by the mobility of the structural constituents. Remarkable changes in mobility can be witnessed with temperature, over narrow, well defined regions, termed relaxation processes. This is an important, unique phenomenon controlling polymer transition behaviour and is described here at an introductory level. The important types of relaxation processes from amorphous to crystalline polymers and polymeric miscible blends are covered, in conjunction with the broad spectrum of experimental methods used to study them in 2007. In-depth discussion of molecular level interpretation, including atomistic level computer simulations and applications to molecular mechanism elucidation, are discussed. The result is a self-contained approach to polymeric interpretation suitable for researchers in materials science, physics and chemistry interested in the relaxation processes of polymeric systems.
Using Molecular Simulations To Understand Polymer Entanglements And Coacervate Phase Behavior
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Author : Sai Vineeth Bobbili
language : en
Publisher:
Release Date : 2021
Using Molecular Simulations To Understand Polymer Entanglements And Coacervate Phase Behavior written by Sai Vineeth Bobbili and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Advancements in computer simulations have led to their application in understanding structure-property relations of polymer melts and solutions. Friction coefficient and entanglement length are two fundamental parameters in modern tube-based theories. In this work, we use molecular dynamics simulations to study the impact of chain architecture and orientation on these two properties. Multiple scaling arguments have been proposed to describe how the entanglement molecular weight depends on polymer architecture and concentration. Such scaling arguments are well supported either by experiments or through simulation data. Each of these arguments makes certain assumptions, which limits their range of validity. Here, we use simulations to explore a wide range of entangled bead-spring ring chains, to find out how entanglement properties vary with chain stiffness and concentration. We quantify entanglement using three techniques: chain shrinking to find the primitive path, measuring the tube diameter by the width of the "cloud" of monomer positions about the primitive path, and directly measuring the plateau modulus. As chain stiffness varies, we observe three distinct scaling regimes, suggestive of the Lin-Noolandi scaling, semiflexible chains, and stiff chains. The packing length p figures prominently in scaling predictions of the entanglement length and bulk modulus for polymer melts and solutions. p has been argued to scale as the ratio of chain displaced volume V and mean square end-to-end distance R^2. This scaling works for several cases; however, it is not obvious how to apply it to chains with side groups, and the scaling must fail for sufficiently thin, stiff chains. In this work, we measure the packing length in simulations, without making any scaling assumptions, as the typical distance of closest approach of two polymer strands in a simulated bead-spring melt using inter-molecular radial distribution functions. While predicting entanglement length has been the focus of several scaling arguments and simulation studies, understanding the behavior of friction coefficient has received less attention. The monomer friction coefficient [zeta] is known to vary with monomer structure, solvent, and concentration; its variation with chain conformation is less well known and appreciated. We explore the decrease of friction coefficient in extensional flow of polymer liquids, during which chains become partially stretched and aligned. In the second half of this dissertation, we use molecular dynamics simulations to investigate the phase behavior of polyelectrolyte complex coacervates. When oppositely charged polyelectrolytes mix in an aqueous solution, associative phase separation gives rise to coacervates. Experiments reveal the phase diagram for such coacervates, and determine the impact of charge density, chain length and added salt. We propose an idealized model and a simple simulation technique to investigate coacervate phase behavior and show the impact of added salt using a phase diagram. Most studies understanding the phase behavior of polyelectrolyte complex coacervates focus on symmetric mixtures of oppositely charged polymers. This is very rare in biological coacervates. Mixing ratio plays an important role in stability of complexes and applications of such coacervates. We use our idealized simulation model to study the impact of charge-asymmetry on the phase behavior of coacervates.
Structure And Rheology Of Molten Polymers
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Author : John M. Dealy
language : en
Publisher: Carl Hanser Verlag GmbH Co KG
Release Date : 2018-02-12
Structure And Rheology Of Molten Polymers written by John M. Dealy and has been published by Carl Hanser Verlag GmbH Co KG this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-02-12 with Technology & Engineering categories.
Recent advances in polymer science have made it possible to relate quantitatively molecular structure to rheological behavior. At the same time, new methods of synthesis and characterization allow the preparation and structural verification of samples having a range of branched polymeric structures. This book unites this knowledge to enable production of polymers with prescribed processability and end-product properties. Methods of polymer synthesis and characterization are described, starting from fundamentals. The foundations of linear viscoelasticity are introduced, and then the linear behavior of entangled polymers is described in detail. This is followed by a discussion of the molecular modeling of linear behavior. Tube models for both linear and branched polymers are presented. The final two chapters deal with nonlinear rheological behavior and tube models to describe nonlinearity. In this second edition, each chapter has been significantly rewritten to account for recent advances in experimental methods and theoretical modeling. It includes new and updated material on developments in polymer synthesis and characterization, computational algorithms for linear and nonlinear rheology prediction, measurement of nonlinear viscoelasticity, entanglement detection algorithms in molecular dynamics, nonlinear constitutive equations, and instabilities. Contents: - Structure of Polymers - Polymerization Reactions and Processes - Linear Viscoelasticity - Fundamentals - Linear Viscoelasticity - Behavior of Molten Polymers - Tube Models for Linear Polymers - Fundamentals - Tube Models for Linear Polymers - Advanced Topics - Determination of Molecular Weight Distribution Using Rheology - Tube Models for Branched Polymers - Nonlinear Viscoelasticity - Tube Models for Nonlinear Viscoelasticity of Linear and Branched Polymers
On The Simulation And Theory Of Polymer Dynamics In Sieving Media
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Author : Martin Kenward
language : en
Publisher:
Release Date : 2007
On The Simulation And Theory Of Polymer Dynamics In Sieving Media written by Martin Kenward and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with University of Ottawa theses categories.
Simulation Studies Of Correlation Functions And Relaxation In Polymeric Systems
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Author :
language : en
Publisher:
Release Date : 2003
Simulation Studies Of Correlation Functions And Relaxation In Polymeric Systems written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
We investigate the statics and dynamics of a glassy, non-entangled, short bead-spring polymer melt with moleculardynamics simulations. Temperature ranges from slightlyabove the mode-coupling critical temperature to the liquidregime where features of a glassy liquid are absent. Ouraim is to work out the polymer specific effects on therelaxation and particle correlation. We find the intra-chain static structure unaffected bytemperature, it depends only on the distance of monomersalong the backbone. In contrast, the distinct inter-chainstructure shows pronounced site-dependence effects at thelength-scales of the chain and the nearest neighbordistance. There, we also find the strongest temperaturedependence which drives the glass transition. Both the siteaveraged coupling of the monomer and center of mass (CM) andthe CM-CM coupling are weak and presumably not responsiblefor a peak in the coherent relaxation time at the chain'slength scale. Chains rather emerge as soft, easilyinterpenetrating objects. Three particle correlations arewell reproduced by the convolution approximation with theexception of model dependent deviations. In the spatially heterogeneous dynamics of our system weidentify highly mobile monomers which tend to follow eachother in one-dimensional paths forming ``strings''. Thesestrings have an exponential length distribution and aregenerally short compared to the chain length. Thus, arelaxation mechanism in which neighboring mobile monomersmove along the backbone of the chain seems unlikely. However, the correlation of bonded neighbors is enhanced. When liquids are confined between two surfaces in relativesliding motion kinetic friction is observed. We study ageneric model setup by molecular dynamics simulations for awide range of sliding speeds, temperatures, loads, andlubricant coverings for simple and molecular fluids. Instabilities in the particle trajectories are identified asthe origin of kinetic friction. They lead to high particlevelocities of flui.
Molecular Dynamic Modeling And Simulation For Polymers
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Author : Anthony F. Harrell
language : en
Publisher:
Release Date : 2003-09
Molecular Dynamic Modeling And Simulation For Polymers written by Anthony F. Harrell and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-09 with Molecular dynamics categories.
Polymers have been widely used in various engineering applications. For more than a quarter century, the materials have been utilized intensively for the binding materials for composites. The material properties of the binding materials called matrix materials play an important role for the composite material behaviors, As a result, the objective of this study was to understand the mechanical properties of polymers. In particular, the goal was to develop insights as to how a molecular level structure is connected to the bulk properties of materials assuming homogeneity. To this end, molecular dynamics was used to model and simulate the polymeric behaviors. Polymeric chains were modeled using the bead and spring model along with interacting potentials. The study examined the effects of different sizes, densities, and numbers of molecules per chain on the shear moduli of the polymers. Furthermore, some preliminary study was also conducted for metallic particle reinforced polymer composites.