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Y Li, S Tang, M Kroger, WK Liu,
Molecular simulation guided constitutive modeling on finite strain viscoelasticity of elastomers
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 88 (2016) 204
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Viscoelasticity characterizes the most important mechanical behavior of elastomers. Understanding the viscoelasticity, especially finite strain viscoelasticity, of elastomers is the key for continuation of their dedicated use in industrial applications. In this work, we present a mechanistic and physics-based constitutive model to describe and design the finite strain viscoelastic behavior of elastomers. Mathematically, the viscoelasticity of elastomers has been decomposed into hyperelastic and viscous parts, which are attributed to the nonlinear deformation of the cross-linked polymer network and the diffusion of free chains, respectively. The hyperelastic deformation of a cross-linked polymer network is governed by the cross-linking density, the molecular weight of the polymer strands between cross-linkages, and the amount of entanglements between different chains, which we observe through large scale molecular dynamics (MD) simulations. Moreover, a recently developed non-affine network model (Davidson and Goulbourne, 2013) is confirmed in the current work to be able to capture these key physical mechanisms using MD simulation. The energy dissipation during a loading and unloading process of elastomers is governed by the diffusion of free chains, which can be understood through their reptation dynamics. The viscous stress can be formulated using the classical tube model (Doi and Edwards, 1986); however, it cannot be used to capture the energy dissipation during finite deformation. By considering the tube deformation during this process, as observed from the MD simulations, we propose a modified tube model to account for the finite deformation behavior of free chains. Combing the non-affine network model for hyper elasticity and modified tube model for viscosity, both understood by molecular simulations, we develop a mechanism-based constitutive model for finite strain viscoelasticity of elastomers. All the parameters in the proposed constitutive model have physical meanings, which are signatures of polymer chemistry, physics or dynamics. Therefore, parametric materials design concepts can be easily gleaned from the model, which is also demonstrated in this study. The finite strain viscoelasticity obtained from our simulations agrees qualitatively with experimental data on both un-vulcanized and vulcanized rubbers, which captures the effects of cross-linking density, the molecular weight of the polymer chain and the strain rate. (C) 2015 Elsevier Ltd. All rights reserved. Kroger, Martin/C-1946-2008; Liu, Wing/B-7599-2009 Kroger, Martin/0000-0003-1402-6714; AFOSR [FA9550-14-1-0032]; NSF of Chongqing [0211002431039]; NSF of China [11472065]; Swiss National Science Foundation [200021_156106]; Office of the Provost; Office for Research; Northwestern University Information Technology We are grateful to Jacob Smith for critical reading of the paper and helpful discussions. Y.L. and W.K.L. warmly thank the support from AFOSR grant No. FA9550-14-1-0032. S.T. thanks NSF of Chongqing (Project no. 0211002431039) and NSF of China (Project no. 11472065). M.K. acknowledges support by the Swiss National Science Foundation through Grant 200021_156106. This research was supported in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. [hide]
Principal Investigators
Leonard Sagis (PL)
Polymer Physics, ETH Zurich, Switzerland ►
Wageningen University, Netherlands ►
Patrick Ilg (PL)
Polymer Physics, ETH Zurich, Switzerland ►
University of Reading, United Kingdom ►
Peter Fischer (Co-PI)
Inst. Food, nutrition and health, ETH Zurich, Switzerland ►
Martin Kröger (PI)
Polymer Physics, ETH Zurich, Switzerland ►
Secretary
Patricia Horn
Polymer Physics, ETH Zurich, Switzerland ►
Involved Students
Ahmad Moghimikheirabadi
Polymer Physics, ETH Zurich, Switzerland ►
Enjoy your reading
LMC Sagis, BX Liu, Y Li, J Essers, J Yang, A Moghimikheirabadi, E Hinderink, C Berton-Carabin, K Schroen,
Dynamic heterogeneity in complex interfaces of soft interface-dominated materials
SCIENTIFIC REPORTS 9 (2019) 2938
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A Moghimikheirabadi, LMC Sagis, M Kroger, P Ilg,
Gas-liquid phase equilibrium of a model Langmuir monolayer captured by a multiscale approach
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 21 (2019) 2295
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PS Stephanou, M Kroger,
Assessment of the Tumbling-Snake Model against Linear and Nonlinear Rheological Data of Bidisperse Polymer Blends
POLYMERS 11 (2019) 376
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SA Vasudevan, A Rauh, M Kroger, M Karg, L Isa,
Dynamics and Wetting Behavior of Core-Shell Soft Particles at a Fluid-Fluid Interface
LANGMUIR 34 (2018) 15370
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YR Sliozberg, IC Yeh, M Kroger, KA Masser, JL Lenhart, JW Andzelm,
Ordering and Crystallization of Entangled Polyethylene Melts under Uniaxial Tension: A Molecular Dynamics Study
MACROMOLECULES 51 (2018) 9635
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J Kirk, M Kroger, P Ilg,
Surface Disentanglement and Slip in a Polymer Melt: A Molecular Dynamics Study
MACROMOLECULES 51 (2018) 8996
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A Moghimikheirabadi, LM Sagis, P Ilg,
Effective interaction potentials for model amphiphilic surfactants adsorbed at fluid-fluid interfaces
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 20 (2018) 16238
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A Ramirez-Hernandez, BL Peters, L Schneider, M Andreev, JD Schieber, M Muller, M Kroger, JJ de Pablo,
A Detailed Examination of the Topological Constraints of Lamellae-Forming Block Copolymers
MACROMOLECULES 51 (2018) 2110
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ZQ Shen, HL Ye, C Zhou, M Kroger, Y Li,
Size of graphene sheets determines the structural and mechanical properties of 3D graphene foams
NANOTECHNOLOGY 29 (2018) 104001
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ZQ Shen, HL Ye, M Kroger, Y Li,
Aggregation of polyethylene glycol polymers suppresses receptor-mediated endocytosis of PEGylated liposomes
NANOSCALE 10 (2018) 4545
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ZQ Shen, HL Ye, M Kroger, Y Li,
Self-assembled core-polyethylene glycol-lipid shell nanoparticles demonstrate high stability in shear flow
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (2017) 13294
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Z Shen, M Roding, M Kroger, Y Li,
Carbon Nanotube Length Governs the Viscoelasticity and Permeability of Buckypaper
POLYMERS 9 (2017) 115
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CF Luo, M Kroger, JU Sommer,
Molecular dynamics simulations of polymer crystallization under confinement: Entanglement effect
POLYMER 109 (2017) 71
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CF Luo, M Kroger, JU Sommer,
Entanglements and Crystallization of Concentrated Polymer Solutions: Molecular Dynamics Simulations
MACROMOLECULES 49 (2016) 9017
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M Schuppler, FC Keber, M Kroger, AR Bausch,
Boundaries steer the contraction of active gels
NATURE COMMUNICATIONS 7 (2016) 13120
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MK Singh, P Ilg, RM Espinosa-Marzal, ND Spencer, M Kroger,
Influence of Chain Stiffness, Grafting Density and Normal Load on the Tribological and Structural Behavior of Polymer Brushes: A Nonequilibrium-Molecular-Dynamics Study
POLYMERS 8 (2016) 254
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YR Sliozberg, M Kroger, TL Chantawansri,
Fast equilibration protocol for million atom systems of highly entangled linear polyethylene chains
JOURNAL OF CHEMICAL PHYSICS 144 (2016) 154901
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PS Stephanou, M Kroger,
Solution of the complete Curtiss-Bird model for polymeric liquids subjected to simple shear flow
JOURNAL OF CHEMICAL PHYSICS 144 (2016) 124905
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ZQ Shen, DT Loe, JK Awino, M Kroger, JL Rouge, Y Li,
Self-assembly of core-polyethylene glycol-lipid shell (CPLS) nanoparticles and their potential as drug delivery vehicles
NANOSCALE 8 (2016) 14821
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A Halperin, M Kroger, FM Winnik,
Poly(N-isopropylacrylamide) Phase Diagrams: Fifty Years of Research
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 54 (2015) 15342
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MK Singh, P Ilg, RM Espinosa-Marzal, M Kroger, ND Spencer,
Polymer Brushes under Shear: Molecular Dynamics Simulations Compared to Experiments
LANGMUIR 31 (2015) 4798
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Selected conferences (co-)organized by project membersIWNET 2015
05 Jul - 10 Jul 2015, 7th International workshop on nonequilibrium thermodynamics (IWNET 2015), Hilvarenbeek, The Netherlands ►IWNET 2018
01 Jul - 06 Jul 2018, 8th International Workshop on Nonequilibrium Thermodynamics (IWNET 2018), Sint-Michielsgestel, The Netherlands ►
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About this project
Complex fluid-fluid interfaces are interfaces in which the adsorbed species self-assemble
into complex microstructures. Such interfaces are ubiquitous in nature, industrial processes,
and consumer products, and can be found in living cells, nano- and microcapsules, vesicles,
food emulsions, or foam. Compared to simple liquid-like interfaces (stabilized by
low molecular weight surfactants), complex interfaces display significant viscoelasticity,
with high values for their surface shear and dilatational moduli. Their stress-deformation
behavior dominates the macroscopic dynamics of multiphase materials that contain
such interfaces, and when this occurs those materials can be referred to as
Interface-Dominated Materials (IDMs).
Complex interfaces can be formed by a wide range of surface active components, such
as proteins, colloidal particles, polymers, lipids, or mixtures of these components.
In this proposal we will focus on complex interfaces stabilized by amphiphilic multi-block
copolymers. These polymers consist of alternating blocks of a hydrophilic repeating unit A,
and a hydrophobic repeating unit B. Amphiphilic copolymers can form interfaces with
exceptional mechanical properties. This makes them ideal candidates for application
in highly stable emulsions, or encapsulation systems with high mechanical stability, for application in food and pharmaceutical products.
Amphiphilic copolymers may form 2d gels, 2d (soft) glass phases, 2d (liquid) crystalline
phases, or even 2d metastable emulsions (phase-separated mixtures of immiscible copolymers)
after adsorption. The type of structure formed depends on surface concentration,
and length, distribution, rigidity, and hydrophobicity of the sub-blocks of the copolymer.
The response of polymer stabilized fluid-fluid interfaces to deformations or gradients in
temperature is often highly nonlinear. The nonlinearity in their response to perturbations
is a result of changes in this interfacial microstructure, induced by the applied
gradients. The effect of deformations on interfacial microstructure, and the effect
of these changes on macroscopic dynamics of interface-dominated materials is still
poorly understood. A more fundamental understanding of the nonlinear response of
polymer interfaces, is essential for a targeted design of high-end polymer stabilized
IDMs, such as encapsulation systems with environmental triggers, nanoparticles with
structured interfaces, or foam and emulsions with extreme stability. In view of the
widespread occurrence of IDMs, the study of dynamic mechanical properties of these
interfaces is highly relevant for many disciplines, such as colloid and interface
science, physical chemistry, polymer physics, pharmaceutical science, food science,
coating technology, or soft matter physics.
The aim of this project is to characterize the microstructure and mechanical properties
of interfaces stabilized by multi-block copolymers, using a multiscale multidisciplinary
approach, which integrates state of the art computational methods with surface rheological
experiments, and experimental interfacial structure evaluation. The computational
modeling will be done using Monte Carlo (MC) and Molecular Dynamics (MD) simulations.
We will measure both shear and dilatational surface properties, and the microstructure
will be evaluated using various forms of microscopy (AFM, TEM, SEM), and neutron
and X-ray reflectivity measurements. We will determine the mechanical properties
and interfacial structure as a function of surface polymer concentration, chemical
structure of the polymers (variation of number, size, and distribution of blocks),
and degree of hydrophobicity and rigidity of the sub-blocks. A detailed insight in
the dynamic behavior of copolymer interfaces will provide new insight in the macroscopic
dynamic behavior of polymer stabilized interface-dominated materials (emulsions,
foam, encapsulation systems, nanoparticles), and will allow a more targeted design
of these systems with tailor made properties, tuned for specific industrial applications.
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