Download or read book Structural Modeling of Dynamic Polymer Networks written by Eric Allen Alt and published by . This book was released on 2019 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer network based gels are an important class of materials with a wide range of applications. Dynamic polymer networks, which crosslink via the formation of reversible bonds, in particular have great potential as stimuli responsive, mechanically tunable, and self-healing materials. Many important emergent properties of these materials, such as mechanical strength, are mediated by their underlying network structure, which can be characterized by the network topology and spatial distribution of nodes. Therefore, unlocking the full potential of these materials through rational design requires an understanding of how network structure arises as a function of network-forming precursor design. Because the bonds that crosslink dynamic polymer networks are reversible, stresses initially present or otherwise induced in these systems can be relieved through network rearrangement. As such, given sufficient time to relax, the network structure is determined by equilibrium thermodynamics. This work presents a thermodynamic formalism which characterizes the free energy of a network in terms of node positional, network topological, and polymer conformational entropies. Through this lens, and aided by numerical calculations and simulations of model networks, we show how the free energy landscape with respect to density relates to factors which can be readily controlled through precursor design, such as polymer length and node size. Additionally, Monte Carlo simulations of explicit networks reveal that thermodynamic relaxation can give rise to spatial heterogeneity in the arrangement of network nodes. In the last chapter we use the tools developed in the earlier chapters to explore how these same design parameters influence the topological statistics of equilibrium networks. In addition to showing how internode connectivity increases with polymer length and system density, we find that inhomogeneity due to spatial relaxation can also lead to greater network connectivity. Finally, we explore the weakening of network topologies due to substitution of polymer-linked node forming components with topologically non-functional counterparts, finding that larger nodes fare better than their smaller counterparts in maintaining network connectivity when these substitutions are made.
Download or read book Structure property Relationships in Dynamic Polymer Networks written by Christopher Brittain Cooper and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many emerging applications including wearable electronics and e-skins, soft robotics and actuators, and biomaterials, require material platforms with precisely controlled mechanical, electrical, thermal, and optical properties. The practical realization of devices for these applications is often restricted not by the lack of novel designs, but rather by the sparsity of materials with the required properties. Dynamic polymers, which employ both permanent and reversible linkages, offer a promising platform for the design of new materials due to their highly tunable and responsive chemical structures. This dissertation explores structure-property relationships in different dynamic polymer networks with well-defined polymer design and is structured as follows. Chapter 1 introduces the concept of dynamic polymers, provides comparisons to supramolecular polymers and segmented block copolymers, and concludes with emerging applications for these systems. Chapter 2 examines the molecular design rules for spontaneous self-assembly of periodic dynamic polymers into supramolecular nanofibers. Chapter 3 discusses the phenomenon of strain-induced supramolecular structures exhibited by entangled periodic dynamic polymers. Chapter 4 highlights how the clustered nanomorphology exhibited by periodic dynamic polymers can be used to design recyclable underwater adhesives. Chapter 5 explains how immiscible dynamic polymers can be used to achieve autonomous alignment of multilayered soft electronics. Chapter 6 concludes with key observations and on the future outlook of next-generation materials.
Download or read book Polymer Networks written by A. Chompff and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: For several decades, polymer science has sought to rationalize the mechanical and thermodynamic properties of polymer networks largely within the framework of statistical thermodynamics. Much of this effort has been directed toward the rubbery rather than the glassy state. It is generally assumed that networks possess an av erage composition to which average properties may be assigned; from such a continuum view, a powerful analysis of such properties as modulus, swelling, birefringence and thermoelasticity has emerged. In the years following the rise of polymer characterization (the late 40's and early 50's), many scientists began to study ap parent relations between the properties of linear polymer molecules and the networks obtainable therefrom. This search was also stimu lated by the wide range of applications of polymer networks in com mercial elastomers, thermosets and coatings. Frequently, these data were confidently matched with curves obtained from statisti cally describable models of networks of ghost chains, uniformly distributed in space. More recently, it has become apparent that polymer chains in networks are not as ideal as assumed in the formulation of statis tical models, and there has been a shift in emphasis towards the less than ideal, perturbed and possibly inhomogeneous networks which are more frequently encountered in practice. The continuum approach, however, had to be developed before inhomogeneous systems could be described; the present volume, therefore, contains both views.
Download or read book Structures and Properties of Rubberlike Networks written by Burak Erman and published by Oxford University Press, USA. This book was released on 1997 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rubber elasticity is an important sub-field of polymer science. This book is in many ways a sequel to the authors' previous, more introductory book, Rubberlike Elasticity: A Molecular Primer (Wiley-Interscience, 1988), and will in some respects replace the now classic book by L.R.G. Treloar, The Physics of Rubber Elasticity (Oxford, 1975). The present book has much in common with its predecessor, in particular its strong emphasis on molecular concepts and theories. Similarly, only equilibrium properties are covered in any detail. Though this book treats much of the same subject matter, it is a more comprehensive, more up-to-date, and somewhat more sophisticated treatment.
Download or read book Design and Understanding of Dynamic Polymer Networks and Polyelectrolyte Complexes written by Junzhe Lou and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Rational design of hydrogels and charged polymers is important for understanding the underlying principles that govern complex mechanical and phase behaviors of biomacromolecular systems. Mimicking and capturing such behaviors in synthetic polymer systems are highly desired for many biomedical and technical applications. Biological tissues exhibit complex dynamic mechanical properties. To capture and control dynamics in synthetic hydrogel scaffolds, I developed a hyaluronic acid (HA)-based dynamic hydrogel system crosslinked by dynamic covalent hydrazone bonds. The HA hydrogels and collagen I generated an interpenetrating network, which exhibited both well-controlled mechanical tunability and fibrillarity, thus providing an adaptable platform to study the cell-matrix interactions. A biocompatible catalyst that accelerates the exchange of hydrazones was then incorporated into the HA-hydrazone hydrogel to modulate the dynamics of crosslinks without affecting network structures. This approach was used to develop injectable hydrogels for cell delivery with high injectability and stability enabled by temporal catalyst controlled hydrogel dynamics. The catalyst control of network dynamics also enabled quantitative and unambiguous correlation between the network parameters and mechanical properties of dynamic polymer networks. In the second part, I investigated the fundamental study on liquid-like polyelectrolyte complexes (PECs) formed by oppositely charged polyelectrolytes. PECs are important in biological systems for membraneless compartments, however the understanding of the mechanism and structure-property relationship is limited. I developed a series of well-defined polymers with tunable structural parameters to modulate the microenvironment of PECs and clearly revealed the importance of local polarity and polyelectrolyte composition on PECs.
Download or read book Dynamics and Transport in Macromolecular Networks written by Li-Tang Yan and published by John Wiley & Sons. This book was released on 2024-04-08 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive knowledge on concepts and experimental advancement, as well as state-of-the-art computational tools and techniques for simulation and theory Dynamics and Transport in Macromolecular Networks: Theory, Modeling, and Experiments provides a unique introduction to the currently emerging, highly interdisciplinary field of those transport processes that exhibit various dynamic patterns and even anomalous behaviors of dynamics, investigating concepts and experimental advancement, as well as state-of-the-art computational tools and techniques for the simulation of macromolecular networks and the transport behavior in them. The detailed text begins with discussions on the structural organization of various macromolecular networks, then moves on to review and consolidate the latest research advances and state-of-the-art tools and techniques for the experimental and theoretical studies of the transport in macromolecular networks. In so doing, the text extracts and emphasizes common principles and research advancement from many different disciplines while providing up-to-date coverage of this new field of research. Written by highly experienced and internationally renowned specialists in various disciplines, such as polymer, soft matter, chemistry, biophysics, and more, Dynamics and Transport in Macromolecular Networks covers sample topics such as: Modeling (visco)elasticity macromolecular and biomacromolecular networks, covering statistical and elastic models and permanent biomacromolecular networks Focus on controlled degradation in modeling reactive hydrogels, covering mesoscale modeling of reactive polymer networks and modeling crosslinking due to hydrosilylation reaction Dynamic bonds in associating polymer networks, covering segmental and chain dynamics and phase-separated aggregate dynamics Direct observation of polymer reptation in entangled solutions and junction fluctuations in crosslinked networks, covering tube width fluctuations and dynamic fluctuations of crosslinks A much-needed overview of developments and scientific findings in the transport behaviors in macromolecular networks, Dynamics and Transport in Macromolecular Networks is a highly valuable resource for chemists, physicists, and other scientists and engineers working in fields related to macromolecular network systems, both theoretically and experimentally.
Download or read book Structural Properties of End linked Polymer Networks written by Nisha Gilra and published by . This book was released on 2000 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of probe free chains trapped in polymer networks was also performed using small-angle neutron scattering. The conformational behavior of 70K poly(dimethylsiloxane) (PDMS) probe chains dissolved in 10K, 35K, 70K PDMS networks was studied and it was found that any variation in Rg as a function of mesh size was too small to be detected. It was also determined that network compression induced stiffness in the probe chains at short distances while maintaining Gaussian behavior at long distances.
Download or read book Rubberlike Elasticity written by James E. Mark and published by Cambridge University Press. This book was released on 2007-02-08 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elastomers and rubberlike materials form a critical component in diverse applications that range from tyres to biomimetics and are used in chemical, biomedical, mechanical and electrical engineering. This updated and expanded edition provides an elementary introduction to the physical and molecular concepts governing elastic behaviour, with a particular focus on elastomers. The coverage of fundamental principles has been greatly extended and fully revised, with analogies to more familiar systems such as gases, producing an engaging approach to these phenomena. Dedicated chapters on novel uses of elastomers, covering bioelastomers, filled elastomers and liquid crystalline elastomers, illustrate the established and emerging applications at the forefront of physical science. With a list of experiments and demonstrations, problem sets and solutions, this is a self-contained introduction to the topic for graduate students, researchers and industrialists working in the applied fields of physics and chemistry, polymer science and engineering.
Download or read book Dynamics and Mechanics of Associating Polymer Networks written by Shengchang Tang (Ph. D.) and published by . This book was released on 2016 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Associating polymers have attracted much interest in a variety of applications such as selfhealing materials, biomaterials, rheological modifiers, and actuators. The interplay of polymer topology and sticker chemistry presents significant challenges in understanding the physics of associating polymers across a wide range of time and length scales. This thesis aims to provide new insights into the structure-dynamics-mechanics relationships of associating polymer networks. This thesis first examines diffusion of various types of associating polymers in the gel state through a combination of experiment and theory. By using forced Rayleigh scattering (FRS), phenomenological super-diffusion is revealed as a general feature in associating networks. Experimental findings are quantitatively explained by a simple two-state model that accounts for the interplay of chain diffusion and the dynamic association-dissociation equilibrium of polymer chains with surrounding network. Furthermore, hindered self-diffusion is shown to directly correlate with a deviation from the Maxwellian behavior in materials rheological response on the long time scale. To further understand how sticker dynamics affects the network mechanical properties, a new method referred to as "sticker diffusion and dissociation spectrometry" is developed to quantify the dissociation rate of stickers in the network junctions. It is demonstrated that sticker dissociation is a prerequisite step for sticker exchange that leads to macroscopic stress relaxation. Finally, this thesis explores the use of fluorescence recovery after photobleaching (FRAP) to measure self-diffusion of associating polymers, and a mathematical framework is established. The second part of this thesis focuses on the development of new methods of controlling the mechanical properties of associating networks through engineering the molecular structure of polymer chains. Specifically, topological entanglement is introduced into the network through extending the polymer chains to reach beyond their entanglement threshold. This strategy drastically enhances material's toughness, extensibility, creep resistance and stability in solutions. Various types of coupling chemistries are then explored to fine tune the extent of entanglement. The entanglement effect and the long-time relaxation of materials can be further controlled by introducing branching points into the macromolecules.
Download or read book A Rheological and Structural Study of Polymer Networks written by Marcel Willem Cornelis Petrus Franse and published by Delft University Press. This book was released on 2002 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents of this doctoral dissertation include: primary polymer molecules with a mondisperse distribution of the molecular weights, crosslinks of any functionality, primary polymer molecules with a disperse distribution of the molecular weights, the sol fraction, number and weight average degrees of polymerization, Schulz-Zimm distribution, fractions of ideal networks and dangling ends, molar masses between the crosslinks
Download or read book Constitutive Models for Rubber IV written by Per-Erik Austrell and published by Routledge. This book was released on 2017-12-04 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique properties of elastomeric materials offer numerous advantages in many engineering applications. Elastomeric units are used as couplings or mountings between rigid components, for example in shock absorbers, vibration insulators, flexible joints, seals and suspensions, etc. However, the complicated nature of the behaviour of such material makes it difficult to accurately predict the performance of these units using finite element modelling, for example. It is imperative that constitutive models accurately capture relevant aspects of mechanical behaviour. The latest developments concerning constitutive modelling of rubber is collected in these Proceedings. Topics included in this volume are, Hyperelastic models, Strength, fracture & fatigue, Dynamic properties & the Fletcher-Gent effect, Micro-mechanical & statistical approaches, Stress softening, iscoelasticity, Filler reinforcement, and Tyres, fibre & cord reinforced rubber.
Download or read book Structure and Properties of Crosslinked Polymers written by Gasan M Magomedov and published by Smithers Rapra. This book was released on 2011-03-23 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives a fresh point of view on the curing processes, structure and properties of crosslinked polymers. The general view is that the structure and properties of crosslinked polymers are defined by their density, this book demonstrates that the parameters are defined by the supermolecular (a more precisely, supersegmental structure) of the crosslinked polymers.The quantitative relationships of the structures/properties are obtained for these polymers. Using an epoxy polymer as a nanofiller for a nanocomposite is discussed and a new class of polymer is proposed. The introduction of the nanofiller gives variation in the mechanical properties, degree of crystallinity, gas permeability and so on. The use of these crosslinked polymers as natural nanocomposites is proposed. Practical methods of crosslinked polymer's supersegmental structure regulation are considered, and all the changes that this gives their properties are detailed.This book will be of significance to all material scientists and students of material science.
Download or read book Materials for a Sustainable Future written by Trevor M. Letcher and published by Royal Society of Chemistry. This book was released on 2012 with total page 829 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aimed at students, lecturers, researchers, and policy makers, this work describes current developments and points the way forward for new developments regarding materials in our society and how they relate to sustainability.
Download or read book Polymer Networks written by R.F. Stepto and published by Springer. This book was released on 1997-12-31 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by an international team of authors with a strong emphasis on the underlying chemistry, this book forms a timely, concise, and accessible evaluation of the fundamentals of polymer network formation, structure, and properties, and how these three aspects are interrelated.
Download or read book Polymer Networks written by A. Chompff and published by Springer. This book was released on 1971-08-01 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: For several decades, polymer science has sought to rationalize the mechanical and thermodynamic properties of polymer networks largely within the framework of statistical thermodynamics. Much of this effort has been directed toward the rubbery rather than the glassy state. It is generally assumed that networks possess an av erage composition to which average properties may be assigned; from such a continuum view, a powerful analysis of such properties as modulus, swelling, birefringence and thermoelasticity has emerged. In the years following the rise of polymer characterization (the late 40's and early 50's), many scientists began to study ap parent relations between the properties of linear polymer molecules and the networks obtainable therefrom. This search was also stimu lated by the wide range of applications of polymer networks in com mercial elastomers, thermosets and coatings. Frequently, these data were confidently matched with curves obtained from statisti cally describable models of networks of ghost chains, uniformly distributed in space. More recently, it has become apparent that polymer chains in networks are not as ideal as assumed in the formulation of statis tical models, and there has been a shift in emphasis towards the less than ideal, perturbed and possibly inhomogeneous networks which are more frequently encountered in practice. The continuum approach, however, had to be developed before inhomogeneous systems could be described; the present volume, therefore, contains both views.
Download or read book Structure and Rheological Properties of Self associating Polymer Networks written by and published by . This book was released on 2015 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-associating polymers have become a key component within modern material science. The ability of the molecule to add complex material properties has spawned interest in a multitude of applications, including a wide variety of consumer products and most recently within themedical field. Fluid-like viscosity to near solid-like elastic dynamics can be observed within polymeric materials. Relatively small changes in external parameters can result in large transitions in this behavior. The concentration of polymers within solution, the temperature of the material, and the lifetime between the attractive chemical groups are a few factors that contribute to their general properties. Despite being widely utilized, how these systems deform under external stresses and exhibit such a wide range of properties is still poorly understood. The following manuscript describes numerical studies where the response of associating polymers to shear deformation is explored. A computational model using a novel, hybrid molecular dynamics, Monte Carlo (MC) algorithm is employed. Polymer chains are modeled as course-grained, bead-spring systems. The attractive end groups form reversible, physical bonds according to MC rules. At high temperatures the system is shown to behave as a fluid. Decreasing the temperature results in self-assembly, forming a complex network structure that is transient. The nodes of this network consist of aggregates of end groups, while links between aggregates are formed by one or more bridging polymer chains. The aggregation dynamics of end groups vary with temperature and time. As a result, aggregate sizes change frequently throughout the simulation. Master equations are employed, defining changes in the number of aggregates of a certain size in terms of reaction rates. Variations in these rates are shown to give rise to the observed changes in the aggregate distribution that characterizes the transition between fluid to solid-like dynamics. Rheological experiments are then performed to obtain the system's stress response to shear deformation. Studies provide insight on microstructural variations in the network topology that lead to observed phenomena within experimental systems. Data obtained in both the linear and nonlinear regimes are then correlated with observed changes in the material properties.
Download or read book Polymeric Liquids Networks written by William W. Graessley and published by Garland Science. This book was released on 2003-11-20 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymeric Liquids and Networks: Structure and Properties is the first book of two by William W. Graessley that presents a unified view of flexible-chain polymer liquids and networks. The topics of both volumes range from equilibrium properties to dynamic response, finite deformation behavior and non-Newtonian flow. The second book will be titled Polymeric Liquids and Networks: Dynamics and Rheology. These various aspects of the field were developed over the past 70 years by researchers from many academic disciplines. The infusion of fresh viewpoints continually invigorated and enriched the field, making polymeric liquids and networks a truly interdisciplinary subject. The lack of a common terminology and perspective, however, has led to compartmentalization, making it difficult for a newcomer, even one technically trained, to gain a broad appreciation of the field and to see the relationships among its various parts. The aim of these two books, without diluting the substance, is to achieve a desired unity.Polymeric Liquids and Networks emphasizes fundamental principles and a molecular viewpoint. The conceptual basis of theories underlying each topical area is explained with derivations sometimes outlined briefly and sometimes given in detail. Technical terminology is kept to a minimum necessary for coherent presentation. The goal of the text is to provide an informed understanding rather than detailed technical proficiency. Theory, experiment, and simulation are woven together as appropriate for achieving a balanced view. The books are designed to serve academic and industrial needs, consolidating the understanding of topics with both practical and fundamental significance, and written from a technical but non-specialized perspective.The books deal mainly with non-polar and weakly polar species and largely with results derived from experiments on structurally well-defined systems. The objective is not to ignore
