1
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Zhai Q, Gao XY, Lee CS, Ong CY, Yan K, Deng HY, Yang S, Lam CH. Surface mobility gradient and emergent facilitation in glassy films. SOFT MATTER 2024; 20:4389-4394. [PMID: 38757511 DOI: 10.1039/d4sm00221k] [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
Confining glassy polymers into films can substantially modify their local and film-averaged properties. We present a lattice model of film geometry with void-mediated facilitation behaviors but free from any elasticity effect. We analyze the spatially varying viscosity to delineate the transport properties of glassy films. The film mobility measurements reported by Yang et al., Science, 2010, 328, 1676 are successfully reproduced. The flow exhibits a crossover from a simple viscous flow to a surface-dominated regime as the temperature decreases. The propagation of a highly mobile front induced by the free surface is visualized in real space. Our approach provides a microscopic treatment of the observed glassy phenomena.
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Affiliation(s)
- Qiang Zhai
- School of Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an, Shaanxi, 710049, China.
| | - Xin-Yuan Gao
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Chun-Shing Lee
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Chin-Yuan Ong
- School of Physics, Yale University, New Haven, Connecticut, 06520, USA
| | - Ke Yan
- School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
| | - Hai-Yao Deng
- School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, CF24 3AA, Wales, UK.
| | - Sen Yang
- School of Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an, Shaanxi, 710049, China.
| | - Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China.
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2
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Phan AD, Schweizer KS. Effect of the nature of the solid substrate on spatially heterogeneous activated dynamics in glass forming supported films. J Chem Phys 2024; 160:074902. [PMID: 38364012 DOI: 10.1063/5.0188016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Accepted: 01/10/2024] [Indexed: 02/18/2024] Open
Abstract
We extend the force-level elastically collective nonlinear Langevin equation theory to treat the spatial gradients of the alpha relaxation time and glass transition temperature, and the corresponding film-averaged quantities, to the geometrically asymmetric case of finite thickness supported films with variable fluid-substrate coupling. The latter typically nonuniversally slows down motion near the solid-liquid interface as modeled via modification of the surface dynamic free energy caging constraints that are spatially transferred into the film and which compete with the accelerated relaxation gradient induced by the vapor interface. Quantitative applications to the foundational hard sphere fluid and a polymer melt are presented. The strength of the effective fluid-substrate coupling has very large consequences for the dynamical gradients and film-averaged quantities in a film thickness and thermodynamic state dependent manner. The interference of the dynamical gradients of opposite nature emanating from the vapor and solid interfaces is determined, including the conditions for the disappearance of a bulk-like region in the film center. The relative importance of surface-induced modification of local caging vs the generic truncation of the long range collective elastic component of the activation barrier is studied. The conditions for the accuracy and failure of a simple superposition approximation for dynamical gradients in thin films are also determined. The emergence of near substrate dead layers, large gradient effects on film-averaged response functions, and a weak non-monotonic evolution of dynamic gradients in thick and cold films are briefly discussed. The connection of our theoretical results to simulations and experiments is briefly discussed, as is the extension to treat more complex glass-forming systems under nanoconfinement.
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Affiliation(s)
- Anh D Phan
- Faculty of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Vietnam
- Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam
| | - Kenneth S Schweizer
- Departments of Materials Science, Chemistry, Chemical and Biomolecular Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
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3
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Yin J, Forrest JA. Film Thickness Dependent Stability and Glass Transition Temperature of Polymer Films Produced by Physical Vapor Deposition. PHYSICAL REVIEW LETTERS 2023; 130:168101. [PMID: 37154633 DOI: 10.1103/physrevlett.130.168101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/12/2023] [Accepted: 03/17/2023] [Indexed: 05/10/2023]
Abstract
We report measurements of the onset temperature of rejuvenation, T_{onset}, and the fictive temperature, T_{f}, for ultrathin stable polystyrene with thicknesses from 10 to 50 nm prepared by physical vapor deposition. We also measure the T_{g} of these glasses on the first cooling after rejuvenation as well as the density anomaly of the as-deposited material. Both the T_{g} in rejuvenated films and the T_{onset} in stable films decrease with decreasing film thickness. The T_{f} value increases for decreasing film thickness. The density increase typical of stable glasses also decreases with decreasing film thickness. Collectively, the results are consistent with a decrease in apparent T_{g} due to the existence of a mobile surface layer, as well as a decrease in the film stability as the thickness is decreased. The results provide the first self-consistent set of measurements of stability in ultrathin films of stable glass.
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Affiliation(s)
- Junjie Yin
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - James A Forrest
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
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4
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Zhang Q, Li W, Qiao K, Han Y. Surface premelting and melting of colloidal glasses. SCIENCE ADVANCES 2023; 9:eadf1101. [PMID: 36930717 PMCID: PMC10022898 DOI: 10.1126/sciadv.adf1101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
The nature of liquid-to-glass transition is a major puzzle in science. A similar challenge exists in glass-to-liquid transition, i.e., glass melting, especially for the poorly investigated surface effects. Here, we assemble colloidal glasses by vapor deposition and melt them by tuning particle attractions. The structural and dynamic parameters saturate at different depths, which define a surface liquid layer and an intermediate glassy layer. The power-law growth of both layers and melting front behaviors at different heating rates are similar to crystal premelting and melting, suggesting that premelting and melting can be generalized to amorphous solids. The measured single-particle kinetics reveal various features and confirm theoretical predictions for glass surface layer.
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Affiliation(s)
- Qi Zhang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Wei Li
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Kaiyao Qiao
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yilong Han
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
- Hong Kong University of Science and Technology, Shenzhen Research Institute, Shenzhen 518057, China
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5
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Yin J, Pedersen C, Thees MF, Carlson A, Salez T, Forrest JA. Surface and bulk relaxation of vapor-deposited polystyrene glasses. J Chem Phys 2023; 158:094901. [PMID: 36889949 DOI: 10.1063/5.0133668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
We have studied the liquid-like response of the surface of vapor-deposited glassy films of polystyrene to the introduction of gold nanoparticles on the surface. The build-up of polymer material was measured as a function of time and temperature for both as-deposited films, as well as films that have been rejuvenated to become normal glasses cooled from the equilibrium liquid. The temporal evolution of the surface profile is well described by the characteristic power law of capillary-driven surface flows. In all cases, the surface evolution of the as-deposited films and the rejuvenated films is enhanced compared to bulk and is not easily distinguishable from each other. The temperature dependence of the measured relaxation times determined from the surface evolution is found to be quantitatively comparable to similar studies for high molecular weight spincast polystyrene. Comparisons to numerical solutions of the glassy thin film equation provide quantitative estimates of the surface mobility. For temperatures sufficiently close to the glass-transition temperature, particle embedding is also measured and used as a probe of bulk dynamics, and, in particular, bulk viscosity.
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Affiliation(s)
- Junjie Yin
- Department of Physics and Astronomy, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada
| | - Christian Pedersen
- Mechanics Division, Department of Mathematics, University of Oslo, 0316 Oslo, Norway
| | - Michael F Thees
- Department of Physics and Astronomy, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada
| | - Andreas Carlson
- Mechanics Division, Department of Mathematics, University of Oslo, 0316 Oslo, Norway
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33400 Talence, France
| | - James A Forrest
- Department of Physics and Astronomy, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada
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6
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Bonneau H, Arutkin M, Chen R, Forrest JA, Raphaël E, Salez T. On the bridge hypothesis in the glass transition of freestanding polymer films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:8. [PMID: 36856883 DOI: 10.1140/epje/s10189-023-00272-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
Freestanding thin polymer films with high molecular weights exhibit an anomalous decrease in the glass-transition temperature with film thickness. Specifically, in such materials, the measured glass-transition temperature evolves in an affine way with the film thickness, with a slope that weakly depends on the molecular weight. De Gennes proposed a sliding mechanism as the hypothetical dominant relaxation process in these systems, where stress kinks could propagate in a reptation-like fashion through so-called bridges, i.e. from one free interface to the other along the backbones of polymer macromolecules. Here, by considering the exact statistics of finite-sized random walks within a confined box, we investigate in details the bridge hypothesis. We show that the sliding mechanism cannot reproduce the basic features appearing in the experiments, and we exhibit the fundamental reasons behind such a fact.
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Affiliation(s)
- Haggai Bonneau
- Gulliver, CNRS UMR 7083, ESPCI Paris, Univ. PSL, 75005, Paris, France
| | - Maxence Arutkin
- School of Chemistry, Center for the Physics and Chemistry of Living Systems, Ratner Institute for Single Molecule Chemistry, and the Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Rainni Chen
- Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - James A Forrest
- Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Elie Raphaël
- Gulliver, CNRS UMR 7083, ESPCI Paris, Univ. PSL, 75005, Paris, France
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33400, Talence, France.
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7
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Chu W, Yu J, Ren N, Wang Z, Hu L. A fractal structural feature related to dynamic crossover in metallic glass-forming liquids. Phys Chem Chem Phys 2023; 25:4151-4160. [PMID: 36655679 DOI: 10.1039/d2cp04840j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The dynamic crossover in supercooled liquids initially predicted by model coupling theory has been widely accepted, but its underlying structural origin is still an open issue for glass-forming liquids. By molecular dynamics simulations of binary CuZr liquids, the present work verifies that high pressure could enhance this crossover, facilitating the studies on the structural features at the crossover temperature Tc. We discover that the topological connectivity of icosahedral clusters is responsible for this dynamic crossover, rather than all clusters. Tc is the temperature at which the connectivity degree between these clusters reaches a maximum and the dynamic heterogeneity begins to keep stable. Below Tc, the fractal topological structures appear in the medium-range order scale. The icosahedral clusters with a certain connectivity pattern can be regarded as a fractal structural unit. By employing the established fractal analysis method, the fractal dimension D of the icosahedral network is calculated. Our results indicate that the D value increases monotonically with increasing pressure and the fractal behavior of the icosahedral network is an inherent feature of metallic glasses. We also find similar fractal behavior in clusters with high local five-fold symmetry. Our findings shed light on the origin of a dynamic crossover in the deep supercooled region of metallic glasses and also demonstrate the important role of icosahedral clusters in uncovering the fractal behavior of metallic glass.
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Affiliation(s)
- Wei Chu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, 250061, China
| | - Jinhua Yu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, 250061, China
| | - Nannan Ren
- School of Materials Science and Engineering, Anhui University of Technology, Ma'anshan, 243032, Anhui Provence, China
| | - Zheng Wang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, 250061, China
| | - Lina Hu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, 250061, China
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8
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Slade J, Merunka D, Peric M. Radical Diffusion Crossover Phenomenon in Glass-Forming Liquids. J Phys Chem Lett 2022; 13:3510-3515. [PMID: 35417657 DOI: 10.1021/acs.jpclett.2c00305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We studied the diffusivities of a nitroxide radical at various temperatures in six glass-forming molecular liquids by electron spin resonance. By comparing the radical diffusivities and solvent self-diffusivities, we found that the radical diffusivities are lower than the self-diffusivities at high temperatures and approach them at low temperatures in all liquids. This crossover behavior was considered as evidence that a single-molecule diffusion process transforms into a collective process with temperature lowering. The crossover phenomenon was analyzed by a novel, simple diffusion model, combining collective and single-molecule diffusion processes, and it was compared to the Arrhenius crossover phenomenon. The obtained results suggest that future studies of tracer diffusion could contribute to a better understanding of diffusion mechanisms in glass-forming liquids. The proposed diffusion model could be used to study the crossover phenomena of tracer diffusion measured by other techniques, and it could serve as a base for developing more advanced models.
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Affiliation(s)
- Jakov Slade
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
| | - Dalibor Merunka
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
| | - Miroslav Peric
- Department of Physics and Astronomy, California State University, Northridge, Northridge, California 91330, United States
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9
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Spieckermann F, Şopu D, Soprunyuk V, Kerber MB, Bednarčík J, Schökel A, Rezvan A, Ketov S, Sarac B, Schafler E, Eckert J. Structure-dynamics relationships in cryogenically deformed bulk metallic glass. Nat Commun 2022; 13:127. [PMID: 35013192 PMCID: PMC8748940 DOI: 10.1038/s41467-021-27661-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 12/03/2021] [Indexed: 11/21/2022] Open
Abstract
The atomistic mechanisms occurring during the processes of aging and rejuvenation in glassy materials involve very small structural rearrangements that are extremely difficult to capture experimentally. Here we use in-situ X-ray diffraction to investigate the structural rearrangements during annealing from 77 K up to the crystallization temperature in Cu44Zr44Al8Hf2Co2 bulk metallic glass rejuvenated by high pressure torsion performed at cryogenic temperatures and at room temperature. Using a measure of the configurational entropy calculated from the X-ray pair correlation function, the structural footprint of the deformation-induced rejuvenation in bulk metallic glass is revealed. With synchrotron radiation, temperature and time resolutions comparable to calorimetric experiments are possible. This opens hitherto unavailable experimental possibilities allowing to unambiguously correlate changes in atomic configuration and structure to calorimetrically observed signals and can attribute those to changes of the dynamic and vibrational relaxations (α-, β- and γ-transition) in glassy materials. The results suggest that the structural footprint of the β-transition is related to entropic relaxation with characteristics of a first-order transition. Dynamic mechanical analysis data shows that in the range of the β-transition, non-reversible structural rearrangements are preferentially activated. The low-temperature γ-transition is mostly triggering reversible deformations and shows a change of slope in the entropic footprint suggesting second-order characteristics. Understanding of the atomic-scale mechanisms of rejuvenation of bulk metallic glass still remains unclear. Here, using configurational entropy derived from X-ray experiments, authors show a clear picture of the relaxation process during annealing of a metallic glass.
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Affiliation(s)
- Florian Spieckermann
- Department of Materials Science, Chair of Materials Physics, Montanuniversität Leoben, Jahnstraße 12, 8700, Leoben, Austria.
| | - Daniel Şopu
- Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria.,Institut für Materialwissenschaft, Fachgebiet Materialmodellierung, Technische Universität Darmstadt, Otto-Berndt-Strasse 3, Darmstadt, D-64287, Germany
| | - Viktor Soprunyuk
- Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria.,Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090, Vienna, Austria
| | - Michael B Kerber
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090, Vienna, Austria
| | - Jozef Bednarčík
- Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607, Hamburg, Germany.,P. J. Šafarik University in Košice, Faculty of Science, Institute of Physics, Park Angelinum 9, 041 54, Košice, Slovakia
| | - Alexander Schökel
- Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607, Hamburg, Germany
| | - Amir Rezvan
- Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria
| | - Sergey Ketov
- Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria
| | - Baran Sarac
- Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria
| | - Erhard Schafler
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090, Vienna, Austria
| | - Jürgen Eckert
- Department of Materials Science, Chair of Materials Physics, Montanuniversität Leoben, Jahnstraße 12, 8700, Leoben, Austria.,Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria
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10
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Dearman M, Ogbonna ND, Amofa CA, Peters AJ, Lawrence J. Versatile strategies to tailor the glass transition temperatures of bottlebrush polymers. Polym Chem 2022. [DOI: 10.1039/d2py00819j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The glass transition temperature (Tg) of bottlebrush polymers can be controlled via side-chain length, blend composition and brush topology. Elucidating interactions between these parameters and their design rules enables accurate targeting of Tg at arbitrary molecular weights.
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Affiliation(s)
- Michael Dearman
- Department of Chemical Engineering, Louisiana State University, Baton Rouge, 70803, USA
| | - Nduka D. Ogbonna
- Department of Chemical Engineering, Louisiana State University, Baton Rouge, 70803, USA
| | - Chamberlain A. Amofa
- Department of Chemical Engineering, Louisiana State University, Baton Rouge, 70803, USA
| | - Andrew J. Peters
- Department of Chemical Engineering, Louisiana Tech University, Ruston, Louisiana, 71272, USA
| | - Jimmy Lawrence
- Department of Chemical Engineering, Louisiana State University, Baton Rouge, 70803, USA
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11
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White RP, Lipson JEG. The dynamics of freestanding films: predictions for poly(2-chlorostyrene) based on bulk pressure dependence and thoughtful sample averaging. SOFT MATTER 2021; 17:9755-9764. [PMID: 34647951 DOI: 10.1039/d1sm01175h] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this paper we model the segmental relaxation in poly(2-chlorostyrene) 18 nm freestanding films, using only data on bulk samples to characterize the system, and predict film relaxation times (τ) as a function of temperature that are in semi-quantitative agreement with film data. The ability to translate bulk characterization into film predictions is a direct result of our previous work connecting the effects of free surfaces in films with those of changing pressure in the bulk. Our approach combines the Locally Correlated Lattice (LCL) equation of state for prediction of free volume values (Vfree) at any given density (ρ), which are then used in the Cooperative Free Volume (CFV) rate model to predict τ(T, Vfree). A key feature of this work is that we calculate the locally averaged density profile as a function of distance from the surface, ρav(z), using the CFV-predicted lengthscale, Lcoop(z), over which rearranging molecular segments cooperate. As we have shown in the past, ρav(z) is significantly broader than the localized profile, ρ(z), which translates into a relaxation profile, τ(z), exhibiting a breadth that mirrors experimental and simulated results. In addition, we discuss the importance of averaging the log of position dependent relaxation times across a film sample (〈log τ(z)〉), as opposed to averaging the relaxation times, themselves, in order to best approximate a whole sample-averaged value that can be directly compared to experiment.
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Affiliation(s)
- Ronald P White
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - Jane E G Lipson
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
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12
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Mei B, Dell ZE, Schweizer KS. Theory of Transient Localization, Activated Dynamics, and a Macromolecular Glass Transition in Ring Polymer Liquids. ACS Macro Lett 2021; 10:1229-1235. [PMID: 35549053 DOI: 10.1021/acsmacrolett.1c00530] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We construct a segmental scale force level theory for the center-of-mass diffusion constant and corresponding relaxation time for globally compact unconcatenated ring polymer solutions and melts (degree of polymerization N). The approach is based on slowly decaying macromolecular scale intermolecular force dynamic correlations as the origin of their unusual dynamics. Unentangled Rouse, weakly caged, and activated regimes are predicted. The barrier of the activated regime scales linearly with N and as a power law of concentration, which drives a kinetic glass transition on the radius-of-gyration scale. The values of N at the two dynamic crossovers (Rouse to weakly caged, weakly caged to activated) are proportional, with nonuniversality entering mainly via macromolecular volume fraction and dimensionless compressibility. Quantitative comparisons with simulation data reveal good agreement. Aspects of intermediate time dynamics are analyzed, and predictions are made for the conditions required to observe a macromolecular glass transition in the laboratory and on the computer.
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13
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Sasaki T, Tsuzuki Y, Nakane T. A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers. Polymers (Basel) 2021; 13:3424. [PMID: 34641239 PMCID: PMC8512962 DOI: 10.3390/polym13193424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 10/02/2021] [Accepted: 10/03/2021] [Indexed: 11/23/2022] Open
Abstract
The non-Arrhenius behavior of segmental dynamics in glass-forming liquids is one of the most profound mysteries in soft matter physics. In this article, we propose a dynamically correlated network (DCN) model to understand the growing behavior of dynamically correlated regions during cooling, which leads to the viscous slowdown of supercooled liquids. The fundamental concept of the model is that the cooperative region of collective motions has a network structure that consists of string-like parts, and networks of various sizes interpenetrate each other. Each segment undergoes dynamical coupling with its neighboring segments via a finite binding energy. Monte Carlo simulations showed that the fractal dimension of the DCNs generated at different temperatures increased and their size distribution became broader with decreasing temperature. The segmental relaxation time was evaluated based on a power law with four different exponents for the activation energy of rearrangement with respect to the DCN size. The results of the present DCN model are consistent with the experimental results for various materials of molecular and polymeric liquids.
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Affiliation(s)
- Takashi Sasaki
- Department of Materials Science and Engineering, University of Fukui, Fukui 9108507, Japan; (Y.T.); (T.N.)
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14
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The Relationship between Free Volume and Cooperative Rearrangement: From the Temperature-Dependent Neutron Total Scattering Experiment of Polystyrene. Polymers (Basel) 2021; 13:polym13183042. [PMID: 34577943 PMCID: PMC8470135 DOI: 10.3390/polym13183042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/05/2021] [Accepted: 09/06/2021] [Indexed: 11/17/2022] Open
Abstract
Although many theories have been proposed to describe the nature of glass formation, its microscopic picture is still missing. Here, by a combination of neutron scattering and molecular dynamics simulation, we present the temperature-dependent atomic structure variation of polystyrene at the glass formation, free volume and cooperative rearrangement. When it is close to glass formation, the polymer is confined in tubes, whose diameter is the main chain–main chain distance, in a “static cage” from its neighbors. This definition can not only account for the kinetic pathway dependence of Williams-Landel-Ferry (WLF) free volume, but also be testified in a set of six polymers. However, the free volume which allows a monomer to move cannot be found in any frame of its real-space image. Monomers, thus, have to move cooperatively to be out of the cage. During glass formation, dynamic heterogeneity develops, and string-like cooperative rearrangement region (CRR) grows over a long range of time and length scales. All of these CRRs tend to walk through loose “static cages”. Our observation unifies the concepts of free volume and cooperative rearrangement. The former is a statistical average leading to a polydisperse “static cage” formation; while a loose “static cage” provides the way that CRRs move.
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15
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Ghanekarade A, Phan AD, Schweizer KS, Simmons DS. Nature of dynamic gradients, glass formation, and collective effects in ultrathin freestanding films. Proc Natl Acad Sci U S A 2021; 118:e2104398118. [PMID: 34326262 PMCID: PMC8346796 DOI: 10.1073/pnas.2104398118] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular, polymeric, colloidal, and other classes of liquids can exhibit very large, spatially heterogeneous alterations of their dynamics and glass transition temperature when confined to nanoscale domains. Considerable progress has been made in understanding the related problem of near-interface relaxation and diffusion in thick films. However, the origin of "nanoconfinement effects" on the glassy dynamics of thin films, where gradients from different interfaces interact and genuine collective finite size effects may emerge, remains a longstanding open question. Here, we combine molecular dynamics simulations, probing 5 decades of relaxation, and the Elastically Cooperative Nonlinear Langevin Equation (ECNLE) theory, addressing 14 decades in timescale, to establish a microscopic and mechanistic understanding of the key features of altered dynamics in freestanding films spanning the full range from ultrathin to thick films. Simulations and theory are in qualitative and near-quantitative agreement without use of any adjustable parameters. For films of intermediate thickness, the dynamical behavior is well predicted to leading order using a simple linear superposition of thick-film exponential barrier gradients, including a remarkable suppression and flattening of various dynamical gradients in thin films. However, in sufficiently thin films the superposition approximation breaks down due to the emergence of genuine finite size confinement effects. ECNLE theory extended to treat thin films captures the phenomenology found in simulation, without invocation of any critical-like phenomena, on the basis of interface-nucleated gradients of local caging constraints, combined with interfacial and finite size-induced alterations of the collective elastic component of the structural relaxation process.
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Affiliation(s)
- Asieh Ghanekarade
- Department of Chemical, Biological and Materials Engineering, University of South Florida, Tampa, FL 33620
| | - Anh D Phan
- Faculty of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Vietnam;
| | - Kenneth S Schweizer
- Department of Materials Science, University of Illinois, Urbana, IL 61801;
- Department of Chemistry, University of Illinois, Urbana, IL 61801
- Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801
| | - David S Simmons
- Department of Chemical, Biological and Materials Engineering, University of South Florida, Tampa, FL 33620;
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16
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Chatterjee D, Annamareddy A, Ketkaew J, Schroers J, Morgan D, Voyles PM. Fast Surface Dynamics on a Metallic Glass Nanowire. ACS NANO 2021; 15:11309-11316. [PMID: 34152730 DOI: 10.1021/acsnano.1c00500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The dynamics near the surface of glasses can be much faster than in the bulk. We studied the surface dynamics of a Pt-based metallic glass using electron correlation microscopy with sub-nanometer resolution. Our studies show an ∼20 K suppression of the glass transition temperature at the surface. The enhancement in surface dynamics is suppressed by coating the metallic glass with a thin layer of amorphous carbon. Parallel molecular dynamics simulations on Ni80P20 show a similar temperature suppression of the surface glass transition temperature and that the enhanced surface dynamics are arrested by a capping layer that chemically binds to the glass surface. Mobility in the near-surface region occurs via atomic caging and hopping, with a strong correlation between slow dynamics and high cage-breaking barriers and stringlike cooperative motion. Surface and bulk dynamics collapse together as a function of temperature rescaled by their respective glass transition temperatures.
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Affiliation(s)
- Debaditya Chatterjee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ajay Annamareddy
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Jittisa Ketkaew
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States
| | - Jan Schroers
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States
| | - Dane Morgan
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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17
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White RP, Lipson JEG. Dynamics across a Free Surface Reflect Interplay between Density and Cooperative Length: Application to Polystyrene. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02742] [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)
- Ronald P. White
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Jane E. G. Lipson
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
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18
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Zha H, Wang Q, Wang X, Cangialosi D, Zuo B. Enhanced Free Surface Mobility Facilitates the Release of Free-Volume Holes in Thin-Film Polymer Glasses. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02887] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Hao Zha
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Qing Wang
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Xinping Wang
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Daniele Cangialosi
- Centro de Física de Materiales, Paseo Manuel de Lardizabal 5, San Sebastian 20018, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, San Sebastian 20018, Spain
| | - Biao Zuo
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
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19
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DeFelice J, Lipson JEG. The influence of additives on polymer matrix mobility and the glass transition. SOFT MATTER 2021; 17:376-387. [PMID: 33169780 DOI: 10.1039/d0sm01634a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the region near an interface, the microscopic properties of a glass forming liquid may be perturbed from their equilibrium bulk values. In this work, we probe how the interfacial effects of additive particles dispersed in a matrix can influence the local mobility of the material and its glass transition temperature, Tg. Experimental measurements and simulation results indicate that additives, such as nanoparticles, gas molecules, and oligomers, can shift the mobility and Tg of a surrounding polymer matrix (even for relatively small concentrations of additive; e.g., 5-10% by volume) relative to the pure bulk matrix, thus leading to Tg enhancement or suppression. Additives thus provide a potential route for modifying the properties of a polymer material without significantly changing its chemical composition. Here we apply the Limited Mobility (LM) model to simulate a matrix containing additive species. We show that both additive concentration, as well as the strength of its very local influence on the surrounding matrix material, will determine whether the Tg of the system is raised or lowered, relative to the pure matrix. We demonstrate that incorporation of additives into the simple LM simulation method, which has successfully described the behavior of bulk and thin film glassy solids, leads to direct connections with available experimental and simulation results for a broad range of polymer/additive systems.
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Affiliation(s)
- Jeffrey DeFelice
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - Jane E G Lipson
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
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20
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Mei B, Dell ZE, Schweizer KS. Microscopic Theory of Long-Time Center-of-Mass Self-Diffusion and Anomalous Transport in Ring Polymer Liquids. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01737] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Baicheng Mei
- Department of Materials Science, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
| | - Zachary E. Dell
- Department of Physics, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
| | - Kenneth S. Schweizer
- Department of Materials Science, University of Illinois, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
- Department of Chemical & Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
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21
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Dumont D, Soulard P, Salez T, Raphaël E, Damman P. Microscopic Picture of Erosion and Sedimentation Processes in Dense Granular Flows. PHYSICAL REVIEW LETTERS 2020; 125:208002. [PMID: 33258653 DOI: 10.1103/physrevlett.125.208002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 05/28/2020] [Accepted: 09/29/2020] [Indexed: 06/12/2023]
Abstract
Gravity-driven flows of granular matter are involved in a wide variety of situations, ranging from industrial processes to geophysical phenomena, such as avalanches or landslides. These flows are characterized by the coexistence of solid and fluid phases, whose stability is directly related to the erosion and sedimentation occurring at the solid-fluid interface. To describe these mechanisms, we build a microscopic model involving friction, geometry, and a nonlocal cooperativity emerging from the propagation of collisions. This new picture enables us to obtain a detailed description of the exchanges between the fluid and solid phases. The model predicts a phase diagram including the limits of erosion and sedimentation, in quantitative agreement with experiments and discrete-element-method simulations.
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Affiliation(s)
- Denis Dumont
- Laboratoire Interfaces et Fluides Complexes, Université de Mons, 20 Place du Parc, B-7000 Mons, Belgium
| | - Pierre Soulard
- UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, 060-0808 Sapporo, Japan
| | - Elie Raphaël
- UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - Pascal Damman
- Laboratoire Interfaces et Fluides Complexes, Université de Mons, 20 Place du Parc, B-7000 Mons, Belgium
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22
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Fujimoto D, MacFarlane WA, Rottler J. Energy barriers and cooperative motion at the surface of freestanding glassy polystyrene films. J Chem Phys 2020; 153:154901. [PMID: 33092352 DOI: 10.1063/5.0022958] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the near-surface relaxation of freestanding atactic polystyrene films with molecular dynamics simulations. As in previous coarse-grained simulations, relaxation times for backbone segments and phenyl rings are linked to their bulk relaxation times via a power-law coupling relation. Variation of the coupling exponent with distance from the surface is consistent with depth-dependent activation barriers. We also quantify a reduction in dynamical heterogeneity at the interface, which can be interpreted in the framework of cooperative models for glassy dynamics.
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Affiliation(s)
- D Fujimoto
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - W A MacFarlane
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - J Rottler
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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23
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Glass transition and fragility of nanosized polymeric fibers and spheres predicted from a surface-controlled model. Polym J 2020. [DOI: 10.1038/s41428-020-00431-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Phan AD, Jedrzejowska A, Paluch M, Wakabayashi K. Theoretical and Experimental Study of Compression Effects on Structural Relaxation of Glass-Forming Liquids. ACS OMEGA 2020; 5:11035-11042. [PMID: 32455224 PMCID: PMC7241026 DOI: 10.1021/acsomega.0c00860] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 04/22/2020] [Indexed: 06/11/2023]
Abstract
We develop the elastically collective nonlinear Langevin equation theory of bulk relaxation of glass-forming liquids to investigate molecular mobility under compression conditions. The applied pressure restricts more molecular motion and therefore significantly slows down the molecular dynamics when increasing the pressure. We quantitatively determine the temperature and pressure dependence of the structural relaxation time. To validate our model, dielectric spectroscopy experiments for three rigid and nonpolymeric supramolecules are carried out at ambient and elevated pressures. The numerical results quantitatively agree with experimental data.
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Affiliation(s)
- Anh D. Phan
- Faculty
of Materials Science and Engineering, Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam
- Faculty
of Computer Science, Artificial Intelligence Laboratory, Phenikaa University, Hanoi 12116, Vietnam
| | - Agnieszka Jedrzejowska
- Institute
of Physics, University of Silesia, SMCEBI, 75 Puku Piechoty 1a, 41-500 Chorzów, Poland
| | - Marian Paluch
- Institute
of Physics, University of Silesia, SMCEBI, 75 Puku Piechoty 1a, 41-500 Chorzów, Poland
| | - Katsunori Wakabayashi
- Department
of Nanotechnology for Sustainable Energy, School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337, Hyogo, Japan
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25
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Phan AD, Schweizer KS. Theory of Spatial Gradients of Relaxation, Vitrification Temperature and Fragility of Glass-Forming Polymer Liquids Near Solid Substrates. ACS Macro Lett 2020; 9:448-453. [PMID: 35648500 DOI: 10.1021/acsmacrolett.0c00006] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We employ a new force-level statistical mechanical theory to predict spatial gradients of the structural relaxation time and Tg of polymer liquids near microscopically rough and smooth hard surfaces and contrast the results with vapor interface systems. Repulsive rough (smooth) surfaces induce large slowing down (modest speeding up) of the relaxation time compared to the bulk. Nevertheless, a remarkable degree of universality of distinctive dynamical behaviors is predicted for different polymer chemistries and all interfaces, including a double exponential form of the alpha time gradient, power law decoupling of the relaxation time from its bulk value with exponential spatial variation of the exponent, exponential spatial gradient of Tg, weak dependence of normalized Tg gradients on vitrification criterion, and near linear growth with cooling of the slowed down layer thickness near a rough hard interface. The results appear consistent with simulations and experiments, and multiple testable predictions are made.
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Affiliation(s)
- Anh D. Phan
- Faculty of Materials Science and Engineering, Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam
- Faculty of Information Technology, Artificial Intelligence Laboratory, Phenikaa University, Hanoi 12116, Vietnam
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26
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Arutkin M, Raphaël E, Forrest JA, Salez T. Cooperative strings and glassy dynamics in various confined geometries. Phys Rev E 2020; 101:032122. [PMID: 32289913 DOI: 10.1103/physreve.101.032122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 02/27/2020] [Indexed: 11/07/2022]
Abstract
Previously, we developed a minimal model based on random cooperative strings for the relaxation of supercooled liquids in the bulk and near free interfaces, and we recovered some key experimental observations. In this article, after recalling the main ingredients of the cooperative string model, we study the effective glass transition and surface mobility of various experimentally relevant confined geometries: freestanding films, supported films, spherical particles, and cylindrical particles, with free interfaces and/or passive substrates. Finally, by canceling and restarting any cooperative-chain realization reaching the boundary with a smaller number of steps than the bulk cooperativity, we account for a purely attractive substrate, and explore the impact of the latter in the previous geometries.
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Affiliation(s)
- Maxence Arutkin
- Perimeter Institute for Theoretical Physics, 31 Caroline St N, Waterloo, Ontario, Canada N2L 2Y5.,UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - Elie Raphaël
- UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France
| | - James A Forrest
- Perimeter Institute for Theoretical Physics, 31 Caroline St N, Waterloo, Ontario, Canada N2L 2Y5.,UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France.,Department of Physics & Astronomy and Guelph-Waterloo Physics Institute, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
| | - Thomas Salez
- Perimeter Institute for Theoretical Physics, 31 Caroline St N, Waterloo, Ontario, Canada N2L 2Y5.,Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France.,Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 060-0808, Japan
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27
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Chai Y, Salez T, Forrest JA. Using Mw Dependence of Surface Dynamics of Glassy Polymers to Probe the Length Scale of Free-Surface Mobility. Macromolecules 2020. [DOI: 10.1021/acs.macromol.9b01728] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Yu Chai
- Department of Physics, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Hokkaido 060-0808, Japan
| | - James A. Forrest
- Department of Physics & Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada
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28
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Schweizer KS, Simmons DS. Progress towards a phenomenological picture and theoretical understanding of glassy dynamics and vitrification near interfaces and under nanoconfinement. J Chem Phys 2019; 151:240901. [PMID: 31893888 DOI: 10.1063/1.5129405] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The nature of alterations to dynamics and vitrification in the nanoscale vicinity of interfaces-commonly referred to as "nanoconfinement" effects on the glass transition-has been an open question for a quarter century. We first analyze experimental and simulation results over the last decade to construct an overall phenomenological picture. Key features include the following: after a metrology- and chemistry-dependent onset, near-interface relaxation times obey a fractional power law decoupling relation with bulk relaxation; relaxation times vary in a double-exponential manner with distance from the interface, with an intrinsic dynamical length scale appearing to saturate at low temperatures; the activation barrier and vitrification temperature Tg approach bulk behavior in a spatially exponential manner; and all these behaviors depend quantitatively on the nature of the interface. We demonstrate that the thickness dependence of film-averaged Tg for individual systems provides a poor basis for discrimination between different theories, and thus we assess their merits based on the above dynamical gradient properties. Entropy-based theories appear to exhibit significant inconsistencies with the phenomenology. Diverse free-volume-motivated theories vary in their agreement with observations, with approaches invoking cooperative motion exhibiting the most promise. The elastically cooperative nonlinear Langevin equation theory appears to capture the largest portion of the phenomenology, although important aspects remain to be addressed. A full theoretical understanding requires improved confrontation with simulations and experiments that probe spatially heterogeneous dynamics within the accessible 1-ps to 1-year time window, minimal use of adjustable parameters, and recognition of the rich quantitative dependence on chemistry and interface.
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Affiliation(s)
- Kenneth S Schweizer
- Departments of Materials Science, Chemistry and Chemical & Biomolecular Engineering, Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - David S Simmons
- Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, Florida 33620, USA
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29
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Zhang W, Starr FW, Douglas JF. Collective Motion in the Interfacial and Interior Regions of Supported Polymer Films and Its Relation to Relaxation. J Phys Chem B 2019; 123:5935-5941. [PMID: 31192601 PMCID: PMC7430234 DOI: 10.1021/acs.jpcb.9b04155] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To understand the role of collective motion in the often large changes in interfacial molecular mobility observed in polymer films, we investigate the extent of collective motion in the interfacial regions of a thin supported polymer film and within the film interior by molecular dynamics simulation. Contrary to commonly stated expectations, we find that the extent of collective motion, as quantified by string-like molecular exchange motion, is similar in magnitude in the polymer-air interfacial layer as the film interior and distinct from the bulk material. This finding is consistent with Adam-Gibbs description of the segmental dynamics within mesoscopic film regions, where the extent of collective motion is related to the configurational entropy of the film as a whole rather than a locally defined extent of collective motion or configurational entropy.
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Affiliation(s)
- Wengang Zhang
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Department of Physics, Wesleyan University, Middletown, Connecticut 06459-0155, United States
| | - Francis W. Starr
- Department of Physics, Wesleyan University, Middletown, Connecticut 06459-0155, United States
| | - Jack F. Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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30
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Phan AD, Schweizer KS. Influence of Longer Range Transfer of Vapor Interface Modified Caging Constraints on the Spatially Heterogeneous Dynamics of Glass-Forming Liquids. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b00754] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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31
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Sasaki T, Nakane T, Sato A. Segmental dynamics of free-standing and supported polymer thin films predicted from a surface-controlled model. POLYMER 2019. [DOI: 10.1016/j.polymer.2019.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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32
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Chang T, Zhang H, Shen X, Hu Z. Polymer-Polymer Interfacial Perturbation on the Glass Transition of Supported Low Molecular Weight Polystyrene Thin Films. ACS Macro Lett 2019; 8:435-441. [PMID: 35651128 DOI: 10.1021/acsmacrolett.9b00118] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Clarifying interfacial perturbation on polymer relaxation is important for polymer material development. Herein we investigated polymer-polymer interfacial perturbation on low molecular weight (MW) polystyrene (PS) thin film (15-180 nm) glass transition by depositing various polymers atop PS films. Overall, rubbery topcoats induced Tg depression of PS thin film (below 60 nm), while glassy topcoats induced Tg elevation of PS thin film (below 30 nm). Importantly, for the rubbery topcoat, Tg perturbation strength is largely dependent on the Tg difference between interfacial polymers and a larger Tg difference would induce stronger perturbation, while for the glassy topcoat this dependence is inconspicuous. Meanwhile, the interfacial perturbation length during PS glass transition by rubbery topcoats is estimated to be around 8 nm, while it is considered to be about 3.5 nm for glassy topcoats. The different interfacial perturbation length induced by disparate topcoats was accounted for by their different perturbation strength on adjacent PS molecules and disparate interfacial roughness. The results can promote the understanding of polymer interfacial perturbation and benefit the design and development of polymer-based materials.
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Affiliation(s)
- Tongxin Chang
- School of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
- Soft Condensed Matter Physics and Interdisciplinary Research Center, Soochow University, Suzhou 215006, China
- Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, China
| | - Hui Zhang
- School of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
- Soft Condensed Matter Physics and Interdisciplinary Research Center, Soochow University, Suzhou 215006, China
- Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, China
| | - Xuezhen Shen
- School of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
- Soft Condensed Matter Physics and Interdisciplinary Research Center, Soochow University, Suzhou 215006, China
- Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, China
| | - Zhijun Hu
- School of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
- Soft Condensed Matter Physics and Interdisciplinary Research Center, Soochow University, Suzhou 215006, China
- Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, China
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33
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Phan AD, Schweizer KS. Theory of the spatial transfer of interface-nucleated changes of dynamical constraints and its consequences in glass-forming films. J Chem Phys 2019; 150:044508. [PMID: 30709240 DOI: 10.1063/1.5079250] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We formulate a new theory for how caging constraints in glass-forming liquids at a surface or interface are modified and then spatially transferred, in a layer-by-layer bootstrapped manner, into the film interior in the context of the dynamic free energy concept of the Nonlinear Langevin Equation (NLE) theory approach. The dynamic free energy at any mean location (cage center) involves contributions from two adjacent layers where confining forces are not the same. At the most fundamental level of the theory, the caging component of the dynamic free energy varies essentially exponentially with distance from the interface, saturating deep enough into the film with a correlation length of modest size and weak sensitivity to the thermodynamic state. This imparts a roughly exponential spatial variation of all the key features of the dynamic free energy required to compute gradients of dynamical quantities including the localization length, jump distance, cage barrier, collective elastic barrier, and alpha relaxation time. The spatial gradients are entirely of dynamical, not structural or thermodynamic, origin. The theory is implemented for the hard sphere fluid and diverse interfaces which can be a vapor, a rough pinned particle solid, a vibrating (softened) pinned particle solid, or a smooth hard wall. Their basic description at the level of the spatially heterogeneous dynamic free energy is identical, with the crucial difference arising from the first layer where dynamical constraints can be weakened, softened, or hardly changed depending on the specific interface. Numerical calculations establish the spatial dependence and fluid volume fraction sensitivity of the key dynamical property gradients for five different model interfaces. A comparison of the theoretical predictions for the dynamic localization length and glassy modulus with simulations and experiments for systems with a vapor interface reveals good agreement. The present advance sets the stage for using the Elastically Collective NLE theory to make quantitative predictions for the alpha relaxation time gradient, decoupling phenomena, Tg gradient, and many film-averaged properties of both model and experimental (colloids, molecules, and polymers) systems with diverse interfaces and chemical makeup.
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Affiliation(s)
- Anh D Phan
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
| | - Kenneth S Schweizer
- Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
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35
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Lam CH. Deeper penetration of surface effects on particle mobility than on hopping rate in glassy polymer films. J Chem Phys 2018; 149:164909. [PMID: 30384677 DOI: 10.1063/1.5052659] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China
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36
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Sakaue T. Topological free volume and quasi-glassy dynamics in the melt of ring polymers. SOFT MATTER 2018; 14:7507-7515. [PMID: 30152832 DOI: 10.1039/c8sm00968f] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Motivated by recent observations that non-concatenated ring polymers in their dense solution exhibit a glass-like dynamics, we propose a free volume description of the motion of such rings based on the notion of topological volume. We first construct a phenomenological free energy which enables one to quantify the degree of topological crowding measured by the coordination number. Then we pinpoint a key role of the cooperative dynamics of neighboring rings, which is responsible for an anomalous dependence of the global structural relaxation (diffusion) time on ring length. Predictions on molecular weight dependence of both static (ring size, coordination number) and dynamic (relaxation time, diffusion coefficient) quantities are in very good agreement with reported numerical simulations. Throughout the discussion, the entanglement length Ne is assumed to be a unique characteristic length for the topological constraint, and hence, all the physical quantities are universally described in terms of the rescaled chain length N/Ne. Finally, we discuss how the dense solution of rings is analogous to yet different from ordinary glassy systems.
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Affiliation(s)
- Takahiro Sakaue
- Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan.
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37
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Phan AD, Schweizer KS. Dynamic Gradients, Mobile Layers, Tg Shifts, Role of Vitrification Criterion, and Inhomogeneous Decoupling in Free-Standing Polymer Films. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01094] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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38
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White RP, Lipson JEG. Explaining the T,V-dependent dynamics of glass forming liquids: The cooperative free volume model tested against new simulation results. J Chem Phys 2018; 147:184503. [PMID: 29141440 DOI: 10.1063/1.5001714] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this article, we derive a rate model, the "cooperative free volume" (CFV) model, to explain relaxation dynamics in terms of a system's free volume, Vfree, and its temperature, T, over widely varied pressure dependent conditions. In the CFV model, the rate a molecule moves a distance on the order of its own size is dependent on the cooperation of surrounding molecules to open up enough free space. To test CFV, we have generated extensive T,V dependent simulation data for structural relaxation times, τ, on a Kob and Andersen type Lennard-Jones (KA-LJ) fluid. The Vfree = V - Vhc values are obtained by estimating the limiting hard core volume, Vhc, through analysis of the KA-LJ PVT data. We provide the first simulation evidence that shows ln τ to be linearly proportional to 1/Vfree on isotherms, with T-dependent slopes, thus confirming our recent analysis of experimental systems. The linear relationship exhibited by the simulation data is further shown to occur at temperatures both above and below the transition to Arrhenius behavior. We also show that the gas kinetic T-dependent contribution is important in simulation results and that there can be a significant entropic contribution from lingering molecular hard-cores at high T. A key result is that non-Arrhenius relaxation behavior is always exhibited on isobars of the KA-LJ fluid, even at high T. The CFV model predicts all of this behavior over a surprisingly wide range of the KA-LJ T,V space, fitting it with just a single set of three parameters. The CFV approach leads to a framework wherein the number of cooperating particles, and thus, the process free energy of activation, is inversely proportional to Vfree, and this is the foundation for the form of the model's volume contribution, a form that we find to hold for all systems and at all temperatures.
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Affiliation(s)
- Ronald P White
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Jane E G Lipson
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA
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Xu J, Li Y, Wu X, Zuo B, Wang X, Zhang W, Tsui OKC. Thickness of the Surface Mobile Layer with Accelerated Crystallization Kinetics in Poly(ethylene terephthalate) Films: Direct Measurement and Analysis. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b00396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Jianquan Xu
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Yun Li
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Xiaoling Wu
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Biao Zuo
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Xinping Wang
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Wei Zhang
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Ophelia K. C. Tsui
- Department of Physics, Hong Kong University of Science & Technology, Clear Water Bay, Hong Kong, China
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40
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Zhang P, Maldonis JJ, Liu Z, Schroers J, Voyles PM. Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy. Nat Commun 2018; 9:1129. [PMID: 29555920 PMCID: PMC5859095 DOI: 10.1038/s41467-018-03604-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 02/25/2018] [Indexed: 11/08/2022] Open
Abstract
Supercooled liquids exhibit spatial heterogeneity in the dynamics of their fluctuating atomic arrangements. The length and time scales of the heterogeneous dynamics are central to the glass transition and influence nucleation and growth of crystals from the liquid. Here, we report direct experimental visualization of the spatially heterogeneous dynamics as a function of temperature in the supercooled liquid state of a Pt-based metallic glass, using electron correlation microscopy with sub-nanometer resolution. An experimental four-point space-time correlation function demonstrates a growing dynamic correlation length, ξ, upon cooling of the liquid toward the glass transition temperature. ξ as a function of the relaxation time τ are in good agreement with Adam-Gibbs theory, inhomogeneous mode-coupling theory and random first-order transition theory of the glass transition. The same experiments demonstrate the existence of a nanometer thickness near-surface layer with order of magnitude shorter relaxation time than inside the bulk.
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Affiliation(s)
- Pei Zhang
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jason J Maldonis
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Ze Liu
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Jan Schroers
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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41
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Sato A, Sasaki T. Cooperativity of dynamics in supercooled polymeric materials and its temperature dependence predicted from a surface controlled model. Eur Polym J 2018. [DOI: 10.1016/j.eurpolymj.2018.01.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cangialosi D. Glass Transition and Physical Aging of Confined Polymers Investigated by Calorimetric Techniques. RECENT ADVANCES, TECHNIQUES AND APPLICATIONS 2018. [DOI: 10.1016/b978-0-444-64062-8.00013-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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43
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Yoon H, McKenna GB. “Rubbery Stiffening” and Rupture Behavior of Freely Standing Nanometric Thin PIB Films. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b02009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Heedong Yoon
- Department of Chemical Engineering,
Whitacre College of Engineering, Texas Tech University, Lubbock, Texas 79409-4121, United States
| | - Gregory B. McKenna
- Department of Chemical Engineering,
Whitacre College of Engineering, Texas Tech University, Lubbock, Texas 79409-4121, United States
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Madkour S, Szymoniak P, Hertwig A, Heidari M, von Klitzing R, Napolitano S, Sferrazza M, Schönhals A. Decoupling of Dynamic and Thermal Glass Transition in Thin Films of a PVME/PS Blend. ACS Macro Lett 2017; 6:1156-1161. [PMID: 35650935 DOI: 10.1021/acsmacrolett.7b00625] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The discussions on the nanoconfinement effect on the glass transition and glassy dynamics phenomena have yielded many open questions. Here, the thickness dependence of the thermal glass transition temperature Tgtherm of thin films of a PVME/PS blend is investigated by ellipsometry. Its thickness dependence was compared to that of the dynamic glass transition (measured by specific heat spectroscopy) and the deduced Vogel temperature (T0). While Tgtherm and T0 showed a monotonous increase, with decreasing film thickness, the dynamic glass transition temperature (Tgdyn) measured at a finite frequency showed a nonmonotonous dependence that peaks at 30 nm. This was discussed by assuming different cooperativity length scales at these temperatures, which have different sensitivities to composition and thickness. This nonmonotonous thickness dependence of Tgdyn disappears for frequencies characteristic for T0. Further analysis of the fragility parameter showed a change in the glassy dynamics from strong to fragile, with decreasing film thickness.
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Affiliation(s)
- Sherif Madkour
- Bundesanstalt für Materialforschung und−prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Paulina Szymoniak
- Bundesanstalt für Materialforschung und−prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Andreas Hertwig
- Bundesanstalt für Materialforschung und−prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Mojdeh Heidari
- Fachbereich
für Physik, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
| | - Regine von Klitzing
- Fachbereich
für Physik, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
| | | | | | - Andreas Schönhals
- Bundesanstalt für Materialforschung und−prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
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45
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Sussman DM, Schoenholz SS, Cubuk ED, Liu AJ. Disconnecting structure and dynamics in glassy thin films. Proc Natl Acad Sci U S A 2017; 114:10601-10605. [PMID: 28928147 PMCID: PMC5635874 DOI: 10.1073/pnas.1703927114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nanometrically thin glassy films depart strikingly from the behavior of their bulk counterparts. We investigate whether the dynamical differences between a bulk and thin film polymeric glass former can be understood by differences in local microscopic structure. Machine learning methods have shown that local structure can serve as the foundation for successful, predictive models of particle rearrangement dynamics in bulk systems. By contrast, in thin glassy films, we find that particles at the center of the film and those near the surface are structurally indistinguishable despite exhibiting very different dynamics. Next, we show that structure-independent processes, already present in bulk systems and demonstrably different from simple facilitated dynamics, are crucial for understanding glassy dynamics in thin films. Our analysis suggests a picture of glassy dynamics in which two dynamical processes coexist, with relative strengths that depend on the distance from an interface. One of these processes depends on local structure and is unchanged throughout most of the film, while the other is purely Arrhenius, does not depend on local structure, and is strongly enhanced near the free surface of a film.
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Affiliation(s)
| | | | - Ekin D Cubuk
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94304
| | - Andrea J Liu
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104
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46
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Cao X, Zhang H, Han Y. Release of free-volume bubbles by cooperative-rearrangement regions during the deposition growth of a colloidal glass. Nat Commun 2017; 8:362. [PMID: 28842562 PMCID: PMC5572473 DOI: 10.1038/s41467-017-00428-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 06/28/2017] [Indexed: 11/09/2022] Open
Abstract
Vapor deposition can directly produce ultrastable glasses which are similar to conventional glasses aged over thousands of years. The highly mobile surface layer is believed to accelerate the ageing process of vapor-deposited glasses, but its microscopic kinetics have not been experimentally observed. Here we study the deposition growth kinetics of a two-dimensional colloidal glass at the single-particle level using video microscopy. We observe that newly deposited particles in the surface layer (depth, d < 14 particles) relax via out-of-cage diffusions of individual particles, while particles in the deeper middle layer (14 < d ≲ 100 particles) relax via activation of cooperative-rearrangement regions. These cooperative-rearrangement regions are much larger, more anisotropic and occur more frequently than cooperative-rearrangement regions in the bulk (d ≳ 100 particles) or after deposition. Cooperative-rearrangement regions move towards the surface and released free-volume bubbles at the surface, while the particles within cooperative-rearrangement regions move towards the bulk, resulting in a more compact bulk glass.Vapor deposition can produce ultrastable glasses similar to conventional glasses aged over thousands of years. Here authors study deposition growth kinetics of a two-dimensional colloidal glass and report relatively frequent occurrence of large and anisotropic regions of cooperative rearrangements at intermediate depths from the surface.
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Affiliation(s)
- Xin Cao
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, 999077, SAR, China
| | - Huijun Zhang
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, 999077, SAR, China
| | - Yilong Han
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, 999077, SAR, China.
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47
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Boucher VM, Cangialosi D, Alegría A, Colmenero J. Complex nonequilibrium dynamics of stacked polystyrene films deep in the glassy state. J Chem Phys 2017; 146:203312. [DOI: 10.1063/1.4977207] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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48
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McGraw JD, Klos M, Bridet A, Hähl H, Paulus M, Castillo JM, Horsch M, Jacobs K. Influence of bidisperse self-assembled monolayer structure on the slip boundary condition of thin polymer films. J Chem Phys 2017; 146:203326. [DOI: 10.1063/1.4978676] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Joshua D. McGraw
- Soft Matter Physics Group, Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
- Département de Physique, Ecole Normale Supérieure/PSL Research University, CNRS, 24 Rue Lhomond, 75005 Paris, France
| | - Mischa Klos
- Soft Matter Physics Group, Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Antoine Bridet
- Soft Matter Physics Group, Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Hendrik Hähl
- Soft Matter Physics Group, Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Michael Paulus
- Fakultät Physik/DELTA, TU Dortmund, 44221 Dortmund, Germany
| | - Juan Manuel Castillo
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schrödinger-Strasse 44, 67663 Kaiserslautern, Germany
| | - Martin Horsch
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schrödinger-Strasse 44, 67663 Kaiserslautern, Germany
| | - Karin Jacobs
- Soft Matter Physics Group, Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
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Mirigian S, Schweizer KS. Influence of chemistry, interfacial width, and non-isothermal conditions on spatially heterogeneous activated relaxation and elasticity in glass-forming free standing films. J Chem Phys 2017; 146:203301. [PMID: 28571330 DOI: 10.1063/1.4974766] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Stephen Mirigian
- Departments of Materials Science and Chemistry, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801, USA
| | - Kenneth S. Schweizer
- Departments of Materials Science and Chemistry, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801, USA
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Napolitano S, Glynos E, Tito NB. Glass transition of polymers in bulk, confined geometries, and near interfaces. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:036602. [PMID: 28134134 DOI: 10.1088/1361-6633/aa5284] [Citation(s) in RCA: 247] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
When cooled or pressurized, polymer melts exhibit a tremendous reduction in molecular mobility. If the process is performed at a constant rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass-a solid lacking long-range order. Despite almost 100 years of research on the (liquid/)glass transition, it is not yet clear which molecular mechanisms are responsible for the unique slow-down in molecular dynamics. In this review, we first introduce the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification. We then analyse the impact of connectivity, structure, and chain environment on molecular motion at the length scale of a few monomers, as well as how macromolecular architecture affects the glass transition of non-linear polymers. We then discuss a revised picture of nanoconfinement, going beyond a simple picture based on interfacial interactions and surface/volume ratio. Analysis of a large body of experimental evidence, results from molecular simulations, and predictions from theory supports, instead, a more complex framework where other parameters are relevant. We focus discussion specifically on local order, free volume, irreversible chain adsorption, the Debye-Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature. We end by highlighting the molecular origin of distributions in relaxation times and glass transition temperatures which exceed, by far, the size of a chain. Fast relaxation modes, almost universally present at the free surface between polymer and air, are also remarked upon. These modes relax at rates far larger than those characteristic of glassy dynamics in bulk. We speculate on how these may be a signature of unique relaxation processes occurring in confined or heterogeneous polymeric systems.
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Affiliation(s)
- Simone Napolitano
- Laboratory of Polymer and Soft Matter Dynamics, Faculté des Sciences, Université Libre de Bruxelles (ULB), Boulevard du Triomphe, 1050 Brussels, Belgium
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