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Wang Y, Patil S, Cheng S, Do C. The influence of elongation-induced concentration fluctuations on segmental friction in polymer blends. SOFT MATTER 2024; 20:4257-4269. [PMID: 38757213 DOI: 10.1039/d4sm00219a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
Recent experimental studies have revealed a lack of universality in the extensional behavior of linear polymers, which is not envisioned by classical molecular theories. These surprising findings, particularly the sharp contrast between polymer melts and solutions, have catalyzed the development of new theoretical ideas, including the concept of friction reduction in highly stretched polymer melts. By presenting evidence from rheology and small-angle neutron scattering, this work shows that deformation-induced demixing, which is due to the viscoelastic asymmetry in binary mixtures, contributes to the observed nonuniversality. In the case of polystyrene/oligostyrene blends, demixing increases the effective glass transition temperature of the long chain, leading to an apparent friction enhancement. On the other hand, the opposite case is found for the polystyrene/poly(α-methylstyrene) blend. These results highlight the important influence of deformation-induced concentration fluctuations on polymer segmental friction.
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Affiliation(s)
- Yangyang Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
| | - Shalin Patil
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
| | - Shiwang Cheng
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
| | - Changwoo Do
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Sun R, Yang J, Patil S, Liu Y, Zuo X, Lee A, Yang W, Wang Y, Cheng S. Relaxation dynamics of deformed polymer nanocomposites as revealed by small-angle scattering and rheology. SOFT MATTER 2022; 18:8867-8884. [PMID: 36377377 DOI: 10.1039/d2sm00775d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The relaxation dynamics of polystyrene (PS)/silica nanocomposites after a large step deformation are studied by a combination of small-angle scattering techniques and rheology. Small-angle X-ray scattering measurements and rheology show clear signatures of nanoparticle aggregation that enhances the mechanical properties of the polymer nanocomposites (PNCs) in the linear viscoelastic regime and during the initial phase of stress relaxation along with accelerated relaxation dynamics. Small-angle neutron scattering experiments under the zero-average-contrast condition reveal, however, smaller structural anisotropy in the PNCs than that in the neat polymer matrix, as well as accelerated anisotropy relaxation. In addition, the degrees of anisotropy reduction and relaxation dynamics acceleration increase with increasing nanoparticle loading. These results are in sharp contrast to the prevailing viewpoint of enhanced molecular deformation as the main mechanism for the mechanical enhancement in PNCs. Furthermore, the observed acceleration of stress relaxation and reduction in structural anisotropy point to two types of nonlinear effects in the relaxation dynamics of PNCs at large deformation.
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Affiliation(s)
- Ruikun Sun
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
| | - Jie Yang
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
- College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, P. R. China
| | - Shalin Patil
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
| | - Yun Liu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Andre Lee
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
| | - Wei Yang
- College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, P. R. China
| | - Yangyang Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
| | - Shiwang Cheng
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
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Ma J, Carrillo JMY, Do C, Chen WR, Falus P, Shen Z, Hong K, Sumpter BG, Wang Y. Spatial correlations of entangled polymer dynamics. Phys Rev E 2021; 104:024503. [PMID: 34525580 DOI: 10.1103/physreve.104.024503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 08/03/2021] [Indexed: 11/07/2022]
Abstract
The spatial correlations of entangled polymer dynamics are examined by molecular dynamics simulations and neutron spin-echo spectroscopy. Due to the soft nature of topological constraints, the initial spatial decays of intermediate scattering functions of entangled chains are, to the first approximation, surprisingly similar to those of an unentangled system in the functional forms. However, entanglements reveal themselves as a long tail in the reciprocal-space correlations, implying a weak but persistent dynamic localization in real space. Comparison with a number of existing theoretical models of entangled polymers suggests that they cannot fully describe the spatial correlations revealed by simulations and experiments. In particular, the strict one-dimensional diffusion idea of the original tube model is shown to be flawed. The dynamic spatial correlation analysis demonstrated in this work provides a useful tool for interrogating the dynamics of entangled polymers. Lastly, the failure of the investigated models to even qualitatively predict the spatial correlations of collective single-chain density fluctuations points to a possible critical role of incompressibility in polymer melt dynamics.
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Affiliation(s)
- Jihong Ma
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Jan-Michael Y Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Changwoo Do
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Wei-Ren Chen
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Péter Falus
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble CEDEX 9, France
| | - Zhiqiang Shen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Bobby G Sumpter
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Yangyang Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Wang Y, Wang W, Hong K, Liu Y. Quantification of Deformation-Induced Concentration Fluctuations in Polymeric Liquids by Small-Angle Neutron Scattering. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yangyang Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Weiyu Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Yun Liu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States
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Sun R, Melton M, Safaie N, Ferrier RC, Cheng S, Liu Y, Zuo X, Wang Y. Molecular View on Mechanical Reinforcement in Polymer Nanocomposites. PHYSICAL REVIEW LETTERS 2021; 126:117801. [PMID: 33798376 DOI: 10.1103/physrevlett.126.117801] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 02/19/2021] [Indexed: 06/12/2023]
Abstract
The microscopic origin of mechanical enhancement in polymer nanocomposite (PNC) melts is investigated through the combination of rheology and small-angle neutron scattering. It is shown that in the absence of an extensive particle network, the molecular deformation of polymer chains dominates the stress response on intermediate time scales. Quantitative analyses of small-angle neutron scattering spectra, however, reveal no enhanced structural anisotropy in the PNCs, compared with the pristine polymers under the same deformation conditions. These results demonstrate that the mechanical reinforcement of PNCs is not due to molecular overstraining, but instead a redistribution of strain field in the polymer matrix, akin to the classical picture of hydrodynamic effect of nanoparticles.
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Affiliation(s)
- Ruikun Sun
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, USA
| | - Matthew Melton
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, USA
| | - Niloofar Safaie
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Robert C Ferrier
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, USA
| | - Shiwang Cheng
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, USA
| | - Yun Liu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Yangyang Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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