51
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Wang DH, Wie JJ, Lee KM, White TJ, Tan LS. Impact of Backbone Rigidity on the Photomechanical Response of Glassy, Azobenzene-Functionalized Polyimides. Macromolecules 2014. [DOI: 10.1021/ma402178z] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- David H. Wang
- Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7750, United States
| | - Jeong Jae Wie
- Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7750, United States
| | - Kyung Min Lee
- Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7750, United States
| | - Timothy J. White
- Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7750, United States
| | - Loon-Seng Tan
- Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7750, United States
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52
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Priezjev NV. Dynamical heterogeneity in periodically deformed polymer glasses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:012601. [PMID: 24580249 DOI: 10.1103/physreve.89.012601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Indexed: 06/03/2023]
Abstract
The dynamics of structural relaxation in a model polymer glass subject to spatially homogeneous, time-periodic shear deformation is investigated using molecular dynamics simulations. We study a coarse-grained bead-spring model of short polymer chains below the glass transition temperature. It is found that at small strain amplitudes, the segmental dynamics is nearly reversible over about 10^{4} cycles, while at strain amplitudes above a few percent, polymer chains become fully relaxed after a hundred cycles. At the critical strain amplitude, the transition from slow to fast relaxation dynamics is associated with the largest number of dynamically correlated monomers as indicated by the peak value of the dynamical susceptibility. The analysis of individual monomer trajectories showed that mobile monomers tend to assist their neighbors to become mobile and aggregate into relatively compact transient clusters.
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Affiliation(s)
- Nikolai V Priezjev
- Department of Mechanical and Materials Engineering, Wright State University, Dayton, Ohio 45435, USA
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53
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Jancar J, Hoy RS, Lesser AJ, Jancarova E, Zidek J. Effect of Particle Size, Temperature, and Deformation Rate on the Plastic Flow and Strain Hardening Response of PMMA Composites. Macromolecules 2013. [DOI: 10.1021/ma400965c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Josef Jancar
- CEITEC, Brno University of Technology, 61200 Brno, Czech Republic
| | - Robert S. Hoy
- Department
of Physics, University of South Florida, Tampa, Florida, 33620, United States
| | - Alan J. Lesser
- Department of Polymer Engineering and Science, University of Massachussetts, Amherst, Massachussetts, 01003, United States
| | - Ema Jancarova
- CEITEC, Brno University of Technology, 61200 Brno, Czech Republic
| | - Jan Zidek
- CEITEC, Brno University of Technology, 61200 Brno, Czech Republic
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54
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Chao H, Riggleman RA. Effect of particle size and grafting density on the mechanical properties of polymer nanocomposites. POLYMER 2013. [DOI: 10.1016/j.polymer.2013.07.018] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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55
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Hoy RS, Karayiannis NC. Simple model for chain packing and crystallization of soft colloidal polymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:012601. [PMID: 23944480 DOI: 10.1103/physreve.88.012601] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Indexed: 06/02/2023]
Abstract
We study a simple bead-spring polymer model exhibiting competing crystallization and glass transitions. Constant-pressure molecular dynamics simulations are employed to study phase behavior and morphological order. For adequately slow quench rates, chain systems exhibit a first-order phase transition (crystallization) below a critical temperature T=T(cryst). We observe the formation of close-packed crystallites of FCC and/or HCP order, separated by domain walls, twin defects, and amorphous regions. Such crystal structures closely resemble the corresponding ordered morphologies of athermal polymer packings: fully flexible chains retain random-walk-like configurations in the crystalline state and do not form lamellae, while semiflexible chains do form lamellae. The model presented here is well suited to the modeling of granular and colloidal polymers, in particular for elucidating the factors that dictate the formation of specific ordered morphologies.
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Affiliation(s)
- Robert S Hoy
- Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
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56
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Shavit A, Riggleman RA. Influence of Backbone Rigidity on Nanoscale Confinement Effects in Model Glass-Forming Polymers. Macromolecules 2013. [DOI: 10.1021/ma400210w] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amit Shavit
- Department of Chemical
and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
19104, United States
| | - Robert A. Riggleman
- Department of Chemical
and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
19104, United States
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57
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58
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59
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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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60
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Luo C, Sommer JU. Disentanglement of Linear Polymer Chains Toward Unentangled Crystals. ACS Macro Lett 2013; 2:31-34. [PMID: 35581821 DOI: 10.1021/mz300552x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Large scale and long time molecular dynamics simulations and primitive path analysis are used to investigate the disentanglement of long linear polymer chains during their crystallization from the melt state. In general, two competitive processes, a slow decrease of average entanglement length during cooling caused by stiffening of chains and a strong increase during crystallization, can be observed. In both homogeneous and heterogeneous nucleation, disentanglement occurs via forming folds from locally unentangled segments and continues in postcrystallization processes (slow reorganization), in particular, during annealing. Re-entanglement processes after melting are slow and can lead to memory effects in heating-recooling protocols such as self-seeding.
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Affiliation(s)
- Chuanfu Luo
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Strasse
6, 01069 Dresden, Germany
| | - Jens-Uwe Sommer
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Strasse
6, 01069 Dresden, Germany
- Institut für
Theoretische Physik, Technische Universität Dresden, Zellescher Weg 17, 01062 Dresden, Germany
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61
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Senden DJA, Krop S, van Dommelen JAW, Govaert LE. Rate- and temperature-dependent strain hardening of polycarbonate. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/polb.23165] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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62
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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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63
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Brown E, Nasto A, Athanassiadis AG, Jaeger HM. Strain stiffening in random packings of entangled granular chains. PHYSICAL REVIEW LETTERS 2012; 108:108302. [PMID: 22463461 DOI: 10.1103/physrevlett.108.108302] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Indexed: 05/26/2023]
Abstract
Random packings of granular chains are presented as a model system to investigate the contribution of entanglements to strain stiffening. The chain packings are sheared in uniaxial compression experiments. For short chain lengths, these packings yield when the shear stress exceeds the scale of the confining pressure, similar to granular packings of unconnected particles. In contrast, packings of chains which are long enough to form loops exhibit strain stiffening, in which the effective stiffness of the material increases with strain, similar to many polymer materials. The latter packings can sustain stresses orders-of-magnitude greater than the confining pressure, and do not yield until the chain links break. X-ray tomography measurements reveal that the strain-stiffening packings contain system-spanning clusters of entangled chains.
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Affiliation(s)
- Eric Brown
- James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
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64
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Kaczmarek H, Gałka P, Szalla A. Atomic force microscopy studies of poly(methyl methacrylate) doped with photoinitiator. J Appl Polym Sci 2011. [DOI: 10.1002/app.34811] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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65
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66
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Hoy RS, O'Hern CS. Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:041803. [PMID: 21230304 DOI: 10.1103/physreve.82.041803] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 08/06/2010] [Indexed: 05/30/2023]
Abstract
A simple theory for glassy-polymeric mechanical response that accounts for large-scale chain relaxation is presented. It captures the crossover from perfect-plastic response to Gaussian strain hardening as the degree of polymerization N increases, without invoking entanglements. By relating hardening to interactions on the scale of monomers and chain segments, we correctly predict its magnitude. Strain-activated relaxation arising from the need to maintain constant chain contour length reduces the characteristic relaxation time by a factor ~εN during active deformation at strain rate ε. This prediction is consistent with results from recent experiments and simulations, and we suggest how it may be further tested experimentally.
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Affiliation(s)
- Robert S Hoy
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520-8286, USA.
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67
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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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68
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69
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Senden DJA, van Dommelen JAW, Govaert LE. Strain hardening and its relation to Bauschinger effects in oriented polymers. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/polb.22056] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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70
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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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71
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Warren M, Rottler J. Microscopic view of accelerated dynamics in deformed polymer glasses. PHYSICAL REVIEW LETTERS 2010; 104:205501. [PMID: 20867036 DOI: 10.1103/physrevlett.104.205501] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Indexed: 05/29/2023]
Abstract
A molecular level analysis of segmental trajectories obtained from molecular dynamics simulations is used to obtain the full relaxation time spectrum in aging polymer glasses subject to three different deformation protocols. As in experiments, dynamics can be accelerated by several orders of magnitude, and a narrowing of the distribution of relaxation times during creep is directly observed. Additionally, the acceleration factor describing the transformation of the relaxation time distributions is computed and found to obey a universal dependence on the strain, independent of age and deformation protocol.
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Affiliation(s)
- Mya Warren
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, V6T 1Z1, Canada
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72
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Wendlandt M, Tervoort TA, Suter UW. Strain-hardening modulus of cross-linked glassy poly(methyl methacrylate). ACTA ACUST UNITED AC 2010. [DOI: 10.1002/polb.21979] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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73
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Majumder MK, S R, Mahajan DK, Basu S. Coarse-graining scheme for simulating uniaxial stress-strain response of glassy polymers through molecular dynamics. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011803. [PMID: 20365391 DOI: 10.1103/physreve.81.011803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Indexed: 05/29/2023]
Abstract
Simulation of the deformation of polymers below their glass transition through molecular dynamics provides an useful route to correlate their molecular architecture to deformation behavior. However, present computational capabilities severely restrict the time and length scales that can be simulated when detailed models of these macromolecules are used. Coarse-graining techniques for macromolecular structures intend to make bigger and longer simulations possible by grouping atoms into superatoms and devising ways of determining reasonable force fields for the superatoms in a manner that retains essential macromolecular features relevant to the process under study but jettisons unnecessary details. In this work we systematically develop a coarse-graining scheme aimed at simulating uniaxial stress-strain behavior of polymers below their glass transition. The scheme involves a two step process of obtaining the coarse grained force field parameters above glass transition. This seems to be enough to obtain "faithful" stress-strain responses after quenching to below the glass transition temperature. We apply the scheme developed to a commercially important polymer polystyrene, derive its complete force field parameters and thus demonstrate the effectiveness of the technique.
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Affiliation(s)
- Manoj K Majumder
- Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
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74
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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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75
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Karayiannis NC, Kröger M. Combined molecular algorithms for the generation, equilibration and topological analysis of entangled polymers: methodology and performance. Int J Mol Sci 2009; 10:5054-5089. [PMID: 20087477 PMCID: PMC2808023 DOI: 10.3390/ijms10115054] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 11/17/2009] [Accepted: 11/20/2009] [Indexed: 12/02/2022] Open
Abstract
We review the methodology, algorithmic implementation and performance characteristics of a hierarchical modeling scheme for the generation, equilibration and topological analysis of polymer systems at various levels of molecular description: from atomistic polyethylene samples to random packings of freely-jointed chains of tangent hard spheres of uniform size. Our analysis focuses on hitherto less discussed algorithmic details of the implementation of both, the Monte Carlo (MC) procedure for the system generation and equilibration, and a postprocessing step, where we identify the underlying topological structure of the simulated systems in the form of primitive paths. In order to demonstrate our arguments, we study how molecular length and packing density (volume fraction) affect the performance of the MC scheme built around chain-connectivity altering moves. In parallel, we quantify the effect of finite system size, of polydispersity, and of the definition of the number of entanglements (and related entanglement molecular weight) on the results about the primitive path network. Along these lines we approve main concepts which had been previously proposed in the literature.
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Affiliation(s)
- Nikos Ch. Karayiannis
- Institute for Optoelectronics and Microsystems (ISOM) and ETSII, Universidad Politécnica de Madrid (UPM), José Gutiérrez Abascal 2, E-28006 Madrid, Spain
| | - Martin Kröger
- Polymer Physics, Swiss Federal Institute of Technology, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8049 Zurich, Switzerland
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76
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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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77
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Robbins MO, Hoy RS. Scaling of the strain hardening modulus of glassy polymers with the flow stress. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/polb.21734] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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78
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Makke A, Perez M, Lame O, Barrat JL. Mechanical testing of glassy and rubbery polymers in numerical simulations: Role of boundary conditions in tensile stress experiments. J Chem Phys 2009; 131:014904. [DOI: 10.1063/1.3148381] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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79
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Riggleman RA, Toepperwein GN, Papakonstantopoulos GJ, de Pablo JJ. Dynamics of a Glassy Polymer Nanocomposite during Active Deformation. Macromolecules 2009. [DOI: 10.1021/ma802865n] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robert A. Riggleman
- Department of Chemical Engineering; University of California, Santa Barbara, California 93106; Department of Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin 53706; and Analytical and Systems Division, Arkema Inc. R&D Center, King of Prussia, Pennsylvania 19406
| | - Gregory N. Toepperwein
- Department of Chemical Engineering; University of California, Santa Barbara, California 93106; Department of Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin 53706; and Analytical and Systems Division, Arkema Inc. R&D Center, King of Prussia, Pennsylvania 19406
| | - George J. Papakonstantopoulos
- Department of Chemical Engineering; University of California, Santa Barbara, California 93106; Department of Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin 53706; and Analytical and Systems Division, Arkema Inc. R&D Center, King of Prussia, Pennsylvania 19406
| | - Juan J. de Pablo
- Department of Chemical Engineering; University of California, Santa Barbara, California 93106; Department of Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin 53706; and Analytical and Systems Division, Arkema Inc. R&D Center, King of Prussia, Pennsylvania 19406
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80
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Vorselaars B, Lyulin AV, Michels MAJ. Deforming glassy polystyrene: Influence of pressure, thermal history, and deformation mode on yielding and hardening. J Chem Phys 2009; 130:074905. [DOI: 10.1063/1.3077859] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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81
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Chen K, Schweizer KS. Suppressed segmental relaxation as the origin of strain hardening in polymer glasses. PHYSICAL REVIEW LETTERS 2009; 102:038301. [PMID: 19257400 DOI: 10.1103/physrevlett.102.038301] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Indexed: 05/27/2023]
Abstract
A nanometer scale dynamical theory is proposed for the large amplitude strain hardening phenomenon in polymer glasses. The new physical picture is that external deformation induces anisotropic chain conformations, which modifies interchain packing, resulting in density fluctuation suppression and intensification of localizing dynamical constraints and activation barriers. The resulting stresses are of intermolecular origin and arise primarily from prolongation of segmental relaxation, not single chain entropic rubber elasticity. Theoretical predictions for the magnitude, temperature, and deformation rate dependence of the hardening modulus are consistent with experiments and simulations.
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Affiliation(s)
- Kang Chen
- Department of Materials Science, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801, USA
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82
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83
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Foteinopoulou K, Karayiannis NC, Laso M, Kröger M. Structure, Dimensions, and Entanglement Statistics of Long Linear Polyethylene Chains. J Phys Chem B 2008; 113:442-55. [DOI: 10.1021/jp808287s] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katerina Foteinopoulou
- Institute for Optoelectronics and Microsystems (ISOM) and ETSII, UPM, José Gutiérrez Abascal 2, E-28006 Madrid, Spain
| | - Nikos Ch. Karayiannis
- Institute for Optoelectronics and Microsystems (ISOM) and ETSII, UPM, José Gutiérrez Abascal 2, E-28006 Madrid, Spain
| | - Manuel Laso
- Institute for Optoelectronics and Microsystems (ISOM) and ETSII, UPM, José Gutiérrez Abascal 2, E-28006 Madrid, Spain
| | - Martin Kröger
- Polymer Physics, Department of Materials, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
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84
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Govaert LE, Engels TAP, Wendlandt M, Tervoort TA, Suter UW. Does the strain hardening modulus of glassy polymers scale with the flow stress? ACTA ACUST UNITED AC 2008. [DOI: 10.1002/polb.21579] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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85
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Chen K, Schweizer KS. Microscopic Constitutive Equation Theory for the Nonlinear Mechanical Response of Polymer Glasses. Macromolecules 2008. [DOI: 10.1021/ma800778v] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kang Chen
- Department of Materials Science and Engineering, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801
| | - Kenneth S. Schweizer
- Department of Materials Science and Engineering, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801
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86
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Hoy RS, Robbins MO. Strain hardening of polymer glasses: entanglements, energetics, and plasticity. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:031801. [PMID: 18517408 DOI: 10.1103/physreve.77.031801] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2007] [Indexed: 05/26/2023]
Abstract
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.
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Affiliation(s)
- Robert S Hoy
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
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87
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Hoy RS, Robbins MO. Strain hardening in polymer glasses: limitations of network models. PHYSICAL REVIEW LETTERS 2007; 99:117801. [PMID: 17930472 DOI: 10.1103/physrevlett.99.117801] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Indexed: 05/25/2023]
Abstract
Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.
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Affiliation(s)
- Robert S Hoy
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
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88
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Warren M, Rottler J. Simulations of aging and plastic deformation in polymer glasses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:031802. [PMID: 17930264 DOI: 10.1103/physreve.76.031802] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Indexed: 05/25/2023]
Abstract
We study the effect of physical aging on the mechanical properties of a model polymer glass using molecular dynamics simulations. The creep compliance is determined simultaneously with the structural relaxation under a constant uniaxial load below yield at constant temperature. The model successfully captures universal features found experimentally in polymer glasses, including signatures of mechanical rejuvenation. We analyze microscopic relaxation time scales and show that they exhibit the same aging characteristics as the macroscopic creep compliance. In addition, our model indicates that the entire distribution of relaxation times scales identically with age. Despite large changes in mobility, we observe comparatively little structural change except for a weak logarithmic increase in the degree of short-range order that may be correlated with an observed decrease in aging with increasing load.
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Affiliation(s)
- Mya Warren
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC, V6T 1Z1, Canada.
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