1
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Micro-mechanical properties of foamed polymer rehabilitation material: A molecular dynamics study. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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2
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Wang J, in ’t Veld PJ, Robbins MO, Ge T. Effects of Coarse-Graining on Molecular Simulation of Craze Formation in Polymer Glass. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c01969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jiuling Wang
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | | | - Mark O. Robbins
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ting Ge
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
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3
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Nan K, Abritta P, Hoy RS. How Does the Character of Glassy-Polymeric Cavitation Depend on Entanglement Density and the Local Poisson Ratio? Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01128] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kai Nan
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Pedro Abritta
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Robert S. Hoy
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
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4
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Kwon T, Sung BJ. Confinement effects on the mechanical heterogeneity of polymer fiber glasses. Phys Rev E 2020; 102:052501. [PMID: 33327119 DOI: 10.1103/physreve.102.052501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 10/13/2020] [Indexed: 11/07/2022]
Abstract
Both polymer fiber glasses and bulk polymer glasses exhibit nonlinear mechanical responses under uniaxial deformation. In polymer fibers, however, polymer chains are confined strongly and the surface area is relatively large compared to their volume. The confinement and the surface may lead to the spatially heterogeneous relaxation of chains in polymer fibers. In this work we perform molecular dynamics simulations and investigate the relation between the heterogeneous dynamics and the nonlinear mechanical responses at a molecular level. Our molecular simulations capture successfully not only the nonlinear mechanical response but also the dependence of mechanical properties on the strain rate of typical polymer glasses as in experiments. We find that the local elastic modulus and the nonaffine displacement are spatially heterogeneous in the pre-yield regime, which results in a lower elastic modulus for polymer fibers than bulk polymer glasses. In the post-yield regime, those mechanical properties become relatively homogeneous. Monomers with large nonaffine displacement are localized mainly at the interfacial region in the pre-yield regime while highly nonaffine monomers are distributed throughout the fibers in the post-yield regime. We show that the nonaffine displacement during deformation relates closely to the mechanical response of the polymer fibers. We also find that in the strain-hardening regime there is a significant difference in the energetic contribution to the stress between polymer fibers and bulk polymers, for which the modulus of the strain-hardening regime of the polymer fibers is smaller than that of bulk polymers.
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Affiliation(s)
- Taejin Kwon
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
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5
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Affiliation(s)
- Qing Peng
- Physics Department King Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia
- Researcher at K.A.CARE Energy Research & Innovation Center at Dhahran Dhahran 31261 Saudi Arabia
| | - Binghui Deng
- Manufacturing Technology and Engineering Corning Incorporated Corning NY 14831 USA
| | - Marcel Utz
- School of Chemistry University of Southampton Southampton SO17 1BJ U.K
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6
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Hu C, Lu T, Guo H. Developing a Transferable Coarse-Grained Model for the Prediction of Thermodynamic, Structural, and Mechanical Properties of Polyimides at Different Thermodynamic State Points. J Chem Inf Model 2019; 59:2009-2025. [DOI: 10.1021/acs.jcim.8b00887] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chenchen Hu
- Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Sciences and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Teng Lu
- Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Sciences and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongxia Guo
- Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Sciences and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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7
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Molinari N, Sutton AP, Mostofi AA. Mechanisms of reinforcement in polymer nanocomposites. Phys Chem Chem Phys 2018; 20:23085-23094. [DOI: 10.1039/c8cp03281e] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Qualitatively different stress–strain responses of polymer nanocomposites are shown to result from the dynamical evolution of three principal molecular structural motifs in the polymer–filler network.
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Affiliation(s)
- N. Molinari
- Department of Physics and the Thomas Young Centre for Theory and Simulation of Materials
- Imperial College London
- London SW7 2AZ
- UK
| | - A. P. Sutton
- Department of Physics and the Thomas Young Centre for Theory and Simulation of Materials
- Imperial College London
- London SW7 2AZ
- UK
| | - A. A. Mostofi
- Department of Physics and the Thomas Young Centre for Theory and Simulation of Materials
- Imperial College London
- London SW7 2AZ
- UK
- Department of Materials and the Thomas Young Centre for Theory and Simulation of Materials
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8
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Lin P, Xu Q, Cheng S, Li X, Zhao Z, Sun S, Peng C, Joy A, Wang SQ. Effects of Molecular Weight Reduction on Brittle–Ductile Transition and Elastic Yielding Due to Noninvasive γ Irradiation on Polymer Glasses. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b00238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Panpan Lin
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Quan Xu
- State
Key Laboratory of Heavy Oil Processing, Institute of New Energy Beijing Key Laboratory of Biogas Upgrading Utilization, China University of Petroleum (Beijing), Beijing 102249, China
| | - Shiwang Cheng
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Xiaoxiao Li
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Zhichen Zhao
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shuangyi Sun
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Chao Peng
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Abraham Joy
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shi-Qing Wang
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325-3909, United States
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9
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Zhao Y, Liu J, Li X, Lu Y, Wang SQ. How and Why Polymer Glasses Lose Their Ductility Due to Plasticizers. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02158] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yue Zhao
- Department of Polymer Science
and Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Jianning Liu
- Department of Polymer Science
and Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Xiaoxiao Li
- Department of Polymer Science
and Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Yue Lu
- Department of Polymer Science
and Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shi-Qing Wang
- Department of Polymer Science
and Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
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10
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Nazarychev VM, Lyulin AV, Larin SV, Gofman IV, Kenny JM, Lyulin SV. Correlation between the High-Temperature Local Mobility of Heterocyclic Polyimides and Their Mechanical Properties. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00602] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Victor M. Nazarychev
- Institute
of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi
pr. 31 (V.O.), 199004 St. Petersburg, Russia
| | - Alexey V. Lyulin
- Theory
of Polymers and Soft Matter Group, Technische Universiteit Eindhoven, PO Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Sergey V. Larin
- Institute
of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi
pr. 31 (V.O.), 199004 St. Petersburg, Russia
| | - Iosif V. Gofman
- Institute
of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi
pr. 31 (V.O.), 199004 St. Petersburg, Russia
| | - José M. Kenny
- Institute
of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi
pr. 31 (V.O.), 199004 St. Petersburg, Russia
- Materials
Science and Technology Centre, University of Perugia, Loc. Pentima,
4, 05100 Terni, Italy
| | - Sergey V. Lyulin
- Institute
of Macromolecular Compounds, Russian Academy of Sciences, Bol’shoi
pr. 31 (V.O.), 199004 St. Petersburg, Russia
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11
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Nazarychev VM, Lyulin AV, Larin SV, Gurtovenko AA, Kenny JM, Lyulin SV. Molecular dynamics simulations of uniaxial deformation of thermoplastic polyimides. SOFT MATTER 2016; 12:3972-3981. [PMID: 27033967 DOI: 10.1039/c6sm00230g] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The results of atomistic molecular-dynamics simulations of mechanical properties of heterocyclic polymer subjected to uniaxial deformation are reported. A new amorphous thermoplastic polyimide R-BAPO with a repeat unit consisting of dianhydride 1,3-bis-(3',4,-dicarboxyphenoxy)diphenyl (dianhydride R) and diamine 4,4'-bis-(4''-aminophenoxy)diphenyloxide (diamine BAPO) was chosen for the simulations. Our primary goal was to establish the impact of various factors (sample preparation method, molecular mass, and cooling and deformation rates) on the elasticity modulus. In particular, we found that the elasticity modulus was only slightly affected by the degree of equilibration, the molecular mass and the size of the simulation box. This is most likely due to the fact that the main contribution to the elasticity modulus is from processes on scales smaller than the entanglement length. Essentially, our simulations reproduce the logarithmic dependence of the elasticity modulus on cooling and deformation rates, which is normally observed in experiments. With the use of the temperature dependence analysis of the elasticity modulus we determined the flow temperature of R-BAPO to be 580 K in line with the experimental data available. Furthermore, we found that the application of high external pressure to the polymer sample during uniaxial deformation can improve the mechanical properties of the polyimide. Overall, the results of our simulations clearly demonstrate that atomistic molecular-dynamics simulations represent a powerful and accurate tool for studying the mechanical properties of heterocyclic polymers and can therefore be useful for the virtual design of new materials, thereby supporting cost-effective synthesis and experimental research.
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Affiliation(s)
- V M Nazarychev
- Institute of Macromolecular Compounds, Russian Academy of Sciences, Bol'shoi pr. 31 (V.O.), St. Petersburg, 199004, Russia.
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12
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Lin P, Liu J, Wang SQ. Delineating nature of stress responses during ductile uniaxial extension of polycarbonate glass. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.02.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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13
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Liu J, Lin P, Cheng S, Wang W, Mays JW, Wang SQ. Polystyrene Glasses under Compression: Ductile and Brittle Responses. ACS Macro Lett 2015; 4:1072-1076. [PMID: 35614806 DOI: 10.1021/acsmacrolett.5b00442] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polystyrene of different molecular weights and their binary mixtures are studied in terms of their various mechanical responses to uniaxial compression at different temperatures. PS of Mw = 25 kg/mol is completely brittle until it is above its glass transition temperature Tg. In contrast, upon incorporation of a high molecular weight component, PS mixtures turn from barely ductile a few degrees below its Tg to ductile over 40° below Tg. In the upper limit, a PS of Mw = 319 kg/mol yields and undergoes plastic flow, even at T = -70 °C. The observed dependence of mechanical responses on molecular weight and molecular weight distribution can be adequately rationalized by the idea that yielding and plastic compression are caused by chain networking.
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Affiliation(s)
- Jianning Liu
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325, United States
| | - Panpan Lin
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325, United States
| | - Shiwang Cheng
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Weiyu Wang
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jimmy W. Mays
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Shi-Qing Wang
- Department
of Polymer Science, University of Akron, Akron, Ohio 44325, United States
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14
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Lin P, Cheng S, Wang SQ. Strain Hardening During Uniaxial Compression of Polymer Glasses. ACS Macro Lett 2014; 3:784-787. [PMID: 35590699 DOI: 10.1021/mz5004129] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The origin of high mechanical stresses in large deformation of polymer glasses has been elusive because both plasticity and elasticity take place. In this work on the nature of the mechanical responses, we carry out uniaxial compression experiments to make simultaneous mechanical and thermal measurements of polycarbonate. Our results confirm that two factors contribute to the growing mechanical stress in the post-yield regime, which is known as "strain hardening". Besides plastic deformation that is intersegmental in origin, chain tension as an intrasegmental component contributes considerably to the measured stress in post-yield. Such a conclusion modifies the previous consensus regarding the nature of strain hardening in mechanical deformation of polymer glasses.
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Affiliation(s)
- Panpan Lin
- Maurice
Morton Institute
of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shiwang Cheng
- Maurice
Morton Institute
of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shi-Qing Wang
- Maurice
Morton Institute
of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
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15
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Strelnikov IA, Mazo MA, Balabaev NK, Oleinik EF. Computer simulation of rearrangements in chains of glassy polymethylene subjected at low temperature inelastic deformation. POLYMER SCIENCE SERIES A 2014. [DOI: 10.1134/s0965545x14030158] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Affiliation(s)
- Shiwang Cheng
- Maurice Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
| | - Shi-Qing Wang
- Maurice Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United States
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17
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Larin SV, Falkovich SG, Nazarychev VM, Gurtovenko AA, Lyulin AV, Lyulin SV. Molecular-dynamics simulation of polyimide matrix pre-crystallization near the surface of a single-walled carbon nanotube. RSC Adv 2014. [DOI: 10.1039/c3ra45010d] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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18
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Rosch TW, Brennan JK, Izvekov S, Andzelm JW. Exploring the ability of a multiscale coarse-grained potential to describe the stress-strain response of glassy polystyrene. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:042606. [PMID: 23679442 DOI: 10.1103/physreve.87.042606] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 03/01/2013] [Indexed: 06/02/2023]
Abstract
A new particle-based bottom-up method to develop coarse-grained models of polymers is presented and applied to polystyrene. The multiscale coarse-graining (MS-CG) technique of Izvekov et al. [J. Chem. Phys. 120, 10896 (2004)] is applied to a polymer system to calculate nonbonded interactions. The inverse Boltzmann inversion method was used to parametrize the bonded and bond-angle bending interactions. Molecular dynamics simulations were performed, and the CG model exhibited a significantly lower modulus compared to the atomistic model at low temperature and high strain rate. In an attempt to improve the CG model performance, several other parametrization schemes were used to build other models from this base model. The first of these models included standard frictional forces through use of the constant-temperature dissipative particle dynamics method that improved the modulus, yet was not transferrable to higher temperatures and lower strain rates. Other models were built by increasing the attraction between CG beads through direct manipulation of the nonbonded potential, where an improvement of the stress response was found. For these models, two parametrization protocols that shifted the force to more attractive values were explored. The first protocol involved a uniform shift, while the other protocol shifted the force in a more localized region. The uniformly shifted potential greatly affected the structure of the equilibrium model as compared to the locally shifted potential, yet was more transferrable to different temperatures and strain rates. Further improvements in the coarse-graining protocol to generate models that more satisfactorily capture mechanical properties are suggested.
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Affiliation(s)
- Thomas W Rosch
- U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005-5066, USA
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19
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Cheng S, Wang SQ. Elastic yielding in cold drawn polymer glasses well below the glass transition temperature. PHYSICAL REVIEW LETTERS 2013; 110:065506. [PMID: 23432274 DOI: 10.1103/physrevlett.110.065506] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 11/30/2012] [Indexed: 06/01/2023]
Abstract
This Letter reports elastic-driven internal yielding in strained ductile polymer glasses. After cold drawing of two different polymer glasses to neck at room temperature, we show that the samples display considerable retractive stress when warmed up above the storage temperature but still considerably below their glass transition temperatures. We conclude that the elastic yielding arises from the distortion of backbones leading to intra-segmental tension in the chain network.
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Affiliation(s)
- Shiwang Cheng
- Maurice Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325, USA
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20
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Zartman GD, Cheng S, Li X, Lin F, Becker ML, Wang SQ. How Melt-Stretching Affects Mechanical Behavior of Polymer Glasses. Macromolecules 2012. [DOI: 10.1021/ma300955h] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gregory D. Zartman
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
| | - Shiwang Cheng
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
| | - Xin Li
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
| | - Fei Lin
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
| | - Matthew L. Becker
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
| | - Shi-Qing Wang
- Morton Institute of Polymer Science and Engineering, University of Akron, Akron, Ohio 44325-3909, United
States
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21
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Chen X, Ye Y, Hao L. Atomistic picture of isothermal volume relaxation behavior of atactic polystyrene glass provided by a molecular dynamics simulation. J Chem Phys 2012; 137:044907. [PMID: 22852655 DOI: 10.1063/1.4737664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using an atomistic molecular dynamics (MD) simulation, we study the volume relaxation behavior of atactic polystyrene and attempt to correlate this macroscopic behavior with certain microscopic aspects. To this end, the gyration radius, the dimensionless relative shape anisotropy, the mean-squared displacement, and the non-Gaussian parameter are examined simultaneously. Our result shows that the structures characterized at different length scales change in a self-similar way and these changes are intimately correlated to the translational mobility of atoms. The initial incubation of structural changes at the different scales originates from the restriction of mobility due to the cage effect. The applicability of the MD simulation to the investigation of the bulk properties is discussed.
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Affiliation(s)
- Xiaoyu Chen
- School of Material Engineering, Jinling Institute of Technology, Nanjing, 211169, People's Republic of China.
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22
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Yang J, Schweizer KS. Glassy dynamics and mechanical response in dense fluids of soft repulsive spheres. II. Shear modulus, relaxation-elasticity connections, and rheology. J Chem Phys 2011; 134:204909. [PMID: 21639479 DOI: 10.1063/1.3592565] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We apply the quiescent and mechanically driven versions of nonlinear Langevin equation theory to study how particle softness influences the shear modulus, the connection between shear elasticity and activated relaxation, and nonlinear rheology of the repulsive Hertzian contact model of dense soft sphere fluids. Below the soft jamming threshold, the shear modulus follows a power law dependence on volume fraction over a narrow interval with an apparent exponent that grows with particle stiffness. To a first approximation, the elastic modulus and transient localization length are controlled by a single coupling constant determined by local fluid structure. In contrast to the behavior of hard spheres, an approximately linear relation between the shear modulus and activation barrier is predicted. This connection has recently been observed for microgel suspensions and provides a microscopic realization of the elastic shoving model. Yielding, shear and stress thinning of the alpha relaxation time and viscosity, and flow curves are also studied. Yield strains are relatively weakly dependent on volume fraction and particle stiffness. Shear thinning commences at values of the effective Peclet number far less than unity, a signature of stress-assisted activated relaxation when barriers are high. Apparent power law reduction of the viscosity with shear rate is predicted with a thinning exponent less than unity. In the vicinity of the soft jamming threshold, a power law flow curve occurs over an intermediate reduced shear rate range with an apparent exponent that decreases as fluid volume fraction and/or repulsion strength increase.
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Affiliation(s)
- Jian Yang
- Department of Materials Science and Frederick Seitz Materials Research Laboratory, University of Illinois, 1304 W. Green Street, Urbana, Illinois 61801, USA
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23
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Metatla N, Soldera A. Effect of the Molar Volume on the Elastic Properties of Vinylic Polymers: A Static Molecular Modeling Approach. MACROMOL THEOR SIMUL 2011. [DOI: 10.1002/mats.201000088] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Léonforte F. Evolution of entanglements during the response to a uniaxial deformation of lamellar triblock copolymers and polymer glasses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:041802. [PMID: 21230303 DOI: 10.1103/physreve.82.041802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2010] [Indexed: 05/30/2023]
Abstract
Using coarse-grained molecular-dynamics simulations, a generic styrene-block-butadiene-block-styrene triblock copolymer under lamellar conformation is used in order to investigate the mutual entanglement evolution when a structure of alternating glassy (S)/rubbery (B) layers is submitted to an imposed deformation. By varying the amount of loop chains between each phase, i.e., noncrossing chains, it is possible to generate different types of S/B interface definitions. A specific boundary driven tensile strain protocol has been developed in order to mimic "real" experiments and measure the stress-strain curve. The same protocol is also applied to a reference state consisting in a directed glassy homopolymers, as well as to an isotropic glassy polymer. The evolution of initial mutual entanglements from the undeformed samples during the whole deformation process is monitored. It is shown for all considered systems that initial entanglements mostly participate to the preyield regime of the stress-strain curve and that this network is debonded during the strain-hardening regime. For triblocks with a non-null amount of crossing chains, the lower the amount is, the longer the memory effect of the initial entanglement network in the postyield regime is. On the fly distributions of entanglements, which depart from the postyield regime, depict memory effects and long-time correlations during the strain-hardening regime. For triblocks, loop chains reinforce these effects.
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Affiliation(s)
- F Léonforte
- Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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25
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Ge T, Robbins MO. Anisotropic plasticity and chain orientation in polymer glasses. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/polb.22015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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27
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MacNeill D, Rottler J. From macroscopic yield criteria to atomic stresses in polymer glasses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011804. [PMID: 20365392 DOI: 10.1103/physreve.81.011804] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Indexed: 05/29/2023]
Abstract
The relationship between macroscopic shear yield criteria and local stress distributions in deformed polymer glasses is investigated via molecular dynamics simulations on different scales of coarse-graining. Macroscopic shear stresses at the yield point obey a pressure-modified von Mises (pmvM) criterion for many different loading conditions and strain rates. Average local stresses in small volume elements obey the same yield criterion for volumes containing approx. 100 atoms or more. Qualitatively different behavior is observed on smaller scales: the average octahedral atomic shear stress has a simple linear relationship to hydrostatic pressure regardless of macroscopic stress state and failure mode. Local plastic events are identified through a threshold in the mean-squared nonaffine displacement and compared to the local stress state. We find that the pmvM criterion only predicts local yield events when stress and displacements are averaged over at least 100 atoms. By contrast, macroscopic shear yield criteria appear to lose their ability to predict plastic activity on the atomic scale.
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Affiliation(s)
- David MacNeill
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
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Hoy RS, Robbins MO. Strain hardening in bidisperse polymer glasses: Separating the roles of chain orientation and interchain entanglement. J Chem Phys 2009; 131:244901. [DOI: 10.1063/1.3276800] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Chen K, Saltzman EJ, Schweizer KS. Segmental dynamics in polymers: from cold melts to ageing and stressed glasses. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:503101. [PMID: 21836211 DOI: 10.1088/0953-8984/21/50/503101] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent progress in developing statistical mechanical theories of supercooled polymer melts and glasses is reviewed. The focus is on those approaches that are either explicitly formulated for polymers, or are applications of more generic theories to interpret polymeric phenomena. These include two configurational entropy theories, a percolated free volume distribution model, and the activated barrier hopping nonlinear Langevin theory. Both chemically-specific and universal aspects are discussed. After a brief summary of classic phenomenological approaches, a discussion of the relevant length scales and key experimental phenomena in both the supercooled liquid and glassy solid state is presented including ageing and nonlinear mechanical response. The central concepts that underlie the theories in the molten state are then summarized and key predictions discussed, including the glass transition in oriented polymer liquids and deformed rubber networks. Physical ageing occurs in the nonequilibrium glass, and theories for its consequences on the alpha relaxation are discussed. Very recent progress in developing a segment scale theory for the dramatic effects of external stress on polymer glasses, including acceleration of relaxation, yielding, plastic flow and strain hardening, is summarized. The article concludes with a discussion of outstanding theoretical challenges.
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Rottler J. Fracture in glassy polymers: a molecular modeling perspective. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:463101. [PMID: 21715863 DOI: 10.1088/0953-8984/21/46/463101] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Over the past 25 years, molecular modeling and simulations have provided important insights into the physics of deformation and fracture of glassy polymers. This review presents an overview of key results discussed in the context of experimentally observed polymer behavior. Both atomistic and coarse-grained polymer models have been used in different deformation protocols to study elastic properties, shear yielding, creep, physical aging, strain hardening and crazing. Simulations reproduce most of the macroscopic features of plasticity in polymer glasses such as stress-strain relations and creep response, and reveal information about the underlying atomistic processes. Trends of the shear yield stress with loading conditions, temperature and strain rate, and the atomistic dynamics under load have been systematically explored. Most polymers undergo physical aging, which leads to a history-dependent mechanical response. Simulations of strain hardening and crazing demonstrate the nature of polymer entanglements in the glassy state and the role of local plasticity and provide insight into the origin of fracture toughness of amorphous polymers.
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Affiliation(s)
- Jörg Rottler
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, V6T 1Z1, Canada
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Buell S, Van Vliet KJ, Rutledge GC. Mechanical Properties of Glassy Polyethylene Nanofibers via Molecular Dynamics Simulations. Macromolecules 2009. [DOI: 10.1021/ma900250y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sezen Buell
- Department of Materials Science and Engineering
- Department of Chemical Engineering
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Krystyn J. Van Vliet
- Department of Materials Science and Engineering
- Department of Chemical Engineering
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Gregory C. Rutledge
- Department of Materials Science and Engineering
- Department of Chemical Engineering
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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