1
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Patel P, Maitra Bhattacharyya S. Effect of the presence of pinned particles on the structural parameters of a liquid and correlation between structure and dynamics at the local level. J Chem Phys 2024; 160:164501. [PMID: 38647308 DOI: 10.1063/5.0191680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 04/04/2024] [Indexed: 04/25/2024] Open
Abstract
Pinning particles at the equilibrium configuration of the liquid is expected not to affect the structure and any property that depends on the structure while slowing down the dynamics. This leads to a breakdown of the structure dynamics correlation. Here, we calculate two structural quantities: the pair excess entropy, S2, and the mean field caging potential, the inverse of which is our structural order parameter (SOP). We show that when the pinned particles are treated the same way as the mobile particles, both S2 and SOP of the mobile particles remain the same as those of the unpinned system, and the structure dynamics correlation decreases with an increase in pinning density, "c." However, when we treat the pinned particles as a different species, even if we consider that the structure does not change, the expression of S2 and SOP changes. The microscopic expressions show that the interaction between a pinned particle and a mobile particle affects S2 and SOP more than the interaction between two mobile particles. We show that a similar effect is also present in the calculation of the excess entropy and is the primary reason for the well-known vanishing of the configurational entropy at high temperatures. We further show that, contrary to the common belief, the pinning process does change the structure. When these two effects are considered, both S2 and SOP decrease with an increase in "c," and the correlation between the structural parameters and the dynamics continues even for higher values of "c."
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Affiliation(s)
- Palak Patel
- Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Sarika Maitra Bhattacharyya
- Polymer Science and Engineering Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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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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Das R, Bhowmik BP, Puthirath AB, Narayanan TN, Karmakar S. Soft pinning: Experimental validation of static correlations in supercooled molecular glass-forming liquids. PNAS NEXUS 2023; 2:pgad277. [PMID: 37680690 PMCID: PMC10482383 DOI: 10.1093/pnasnexus/pgad277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/14/2023] [Indexed: 09/09/2023]
Abstract
Enormous enhancement in the viscosity of a liquid near its glass transition is a hallmark of glass transition. Within a class of theoretical frameworks, it is connected to growing many-body static correlations near the transition, often called "amorphous ordering." At the same time, some theories do not invoke the existence of such a static length scale in the problem. Thus, proving the existence and possible estimation of the static length scales of amorphous order in different glass-forming liquids is very important to validate or falsify the predictions of these theories and unravel the true physics of glass formation. Experiments on molecular glass-forming liquids become pivotal in this scenario as the viscosity grows several folds (∼ 10 14 ), and simulations or colloidal glass experiments fail to access these required long-time scales. Here we design an experiment to extract the static length scales in molecular liquids using dilute amounts of another large molecule as a pinning site. Results from dielectric relaxation experiments on supercooled Glycerol with different pinning concentrations of Sorbitol and Glucose, as well as the simulations on a few model glass-forming liquids with pinning sites, indicate the versatility of the proposed method, opening possible new avenues to study the physics of glass transition in other molecular liquids.
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Affiliation(s)
- Rajsekhar Das
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, USA
- TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India
| | - Bhanu Prasad Bhowmik
- TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India
- Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Anand B Puthirath
- TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Tharangattu N Narayanan
- TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India
| | - Smarajit Karmakar
- TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India
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4
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Merrill JH, Li R, Roth CB. End-Tethered Chains Increase the Local Glass Transition Temperature of Matrix Chains by 45 K Next to Solid Substrates Independent of Chain Length. ACS Macro Lett 2023; 12:1-7. [PMID: 36516977 DOI: 10.1021/acsmacrolett.2c00582] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The local glass transition temperature Tg of pyrene-labeled polystyrene (PS) chains intermixed with end-tethered PS chains grafted to a neutral silica substrate was measured by fluorescence spectroscopy. To isolate the impact of the grafted chains, the films were capped with bulk neat PS layers eliminating competing effects of the free surface. Results demonstrate that end-grafted chains strongly increase the local Tg of matrix chains by ≈45 K relative to bulk Tg, independent of grafted chain molecular weight from Mn = 8.6 to 212 kg/mol and chemical end-group, over a wide range of grafting densities σ = 0.003 to 0.33 chains/nm2 spanning the mushroom-to-brush transition regime. The tens-of-degree increase in local Tg resulting from immobilization of the chain ends by covalent bonding in this athermal system suggests a mechanism that substantially increases the local activation energy required for cooperative rearrangements.
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Affiliation(s)
- James H Merrill
- Department of Physics, Emory University, Atlanta, Georgia30322, United States
| | - Ruoyu Li
- Department of Physics, Emory University, Atlanta, Georgia30322, United States
| | - Connie B Roth
- Department of Physics, Emory University, Atlanta, Georgia30322, United States
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5
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Singh A, Singh Y. Structure ordering and glass transition in size-asymmetric ternary mixtures of hard spheres: Variation from fragile to strong glasses. Phys Rev E 2023; 107:014119. [PMID: 36797956 DOI: 10.1103/physreve.107.014119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/21/2022] [Indexed: 01/15/2023]
Abstract
We investigate the structure and activated dynamics of a binary mixture of colloidal particles dispersed in a solvent of much smaller-sized particles. The solvent degrees of freedom are traced out from the grand partition function of the colloid-solvent mixture which reduces the system from ternary to effective binary mixture of colloidal particles. In the effective binary mixture colloidal particles interact via effective potential that consists of bare potential plus the solvent-induced interaction. Expressions for the effective potentials and pair correlation functions are derived. We used the result of pair correlation functions to determine the number of particles in a cooperatively reorganizing cluster (CRC) in which localized particles form "long-lived" nonchemical bonds with the central particle. For an event of relaxation to take place these bonds have to reorganize irreversibly, the energy involved in the processes is the effective activation energy of relaxation. Results are reported for hard sphere colloidal particles dispersed in a solvent of hard sphere particles. Our results show that the concentration of solvent can be used as a control parameter to fine-tune the microscopic structural ordering and the size of CRC that governs the glassy dynamics. We show that a small variation in the concentration of solvent creates a bigger change in the kinetic fragility which highlights a wide variation in behavior, ranging from fragile to strong glasses. We conclude that the CRC which is determined from the static pair correlation function and the fluctuations embedded in the system is probably the sole player in the physics of glass transition.
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Affiliation(s)
- Ankit Singh
- Department of Physics, Banaras Hindu University, Varanasi 221 005, India
| | - Yashwant Singh
- Department of Physics, Banaras Hindu University, Varanasi 221 005, India
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6
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Phan AD. Screening and collective effects in randomly pinned fluids: a new theoretical framework. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:435101. [PMID: 35985315 DOI: 10.1088/1361-648x/ac8b51] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 08/19/2022] [Indexed: 06/15/2023]
Abstract
We propose a theoretical framework for the dynamics of bulk isotropic hard-sphere systems in the presence of randomly pinned particles and apply this theory to supercooled water to validate it. Structural relaxation is mainly governed by local and non-local activated process. As the pinned fraction grows, a local caging constraint becomes stronger and the long range collective aspect of relaxation is screened by immobile obstacles. Different responses of the local and cooperative motions results in subtle predictions for how the alpha relaxation time varies with pinning and density. Our theoretical analysis for the relaxation time of water with pinned molecules quantitatively well describe previous simulations. In addition, the thermal dependence of relaxation for unpinned bulk water is also consistent with prior computational and 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
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7
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Mei B, Lin TW, Sheridan GS, Evans CM, Sing CE, Schweizer KS. Structural Relaxation and Vitrification in Dense Cross-Linked Polymer Networks: Simulation, Theory, and Experiment. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c00277] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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
| | - Tsai-Wei Lin
- Department of Chemical & Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
| | - Grant S. Sheridan
- Department of Materials Science, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
| | - Christopher M. Evans
- Department of Materials Science, 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
| | - Charles E. Sing
- Department of Materials Science, 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
| | - 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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8
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Phan AD. Confinement Effects on the Spatially Inhomogeneous Dynamics in Metallic Glass Films. J Phys Chem B 2022; 126:1609-1614. [PMID: 35166111 DOI: 10.1021/acs.jpcb.1c08862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work develops the elastically collective nonlinear Langevin equation theory to investigate, for the first time, the glassy dynamics in capped metallic glass thin films. Finite-size effects on the spatial gradient of structural relaxation time and glass transition temperature (Tg) are calculated at different temperatures and vitrification criteria. Molecular dynamics is significantly slowed down near rough solid surfaces, and the dynamics at location far from the interfaces is sped up. In thick films, the mobility gradient normalized by the bulk value obeys the double-exponential form since interference effects between two surfaces are weak. Reducing the film thickness induces a strong dynamic coupling between two surfaces and flattens the relaxation gradient. The normalized gradient of the glass transition temperature is independent of vitrification time scale criterion and can be fitted by a superposition function as the films are not ultrathin. The local fragility is found to remain unchanged with location. This finding suggests that one can use Angell plots of bulk relaxation time and the Tg spatial gradient to characterize glassy dynamics in metallic glass films. Our computational results agree well with experimental data and simulation.
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Affiliation(s)
- Anh D Phan
- Faculty of Materials Science and Engineering, Computer Science, Artificial Intelligence Laboratory, Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam
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9
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Mei B, Schweizer KS. Activated penetrant dynamics in glass forming liquids: size effects, decoupling, slaving, collective elasticity and correlation with matrix compressibility. SOFT MATTER 2021; 17:2624-2639. [PMID: 33528485 DOI: 10.1039/d0sm02215b] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We employ the microscopic self-consistent cooperative hopping theory of penetrant activated dynamics in glass forming viscous liquids and colloidal suspensions to address new questions over a wide range of high matrix packing fractions and penetrant-to-matrix particle size ratios. The focus is on the mean activated relaxation time of smaller tracers in a hard sphere fluid of larger particle matrices. This quantity also determines the penetrant diffusion constant and connects directly with the structural relaxation time probed in an incoherent dynamic structure factor measurement. The timescale of the non-activated fast dissipative process is also studied and is predicted to follow power laws with the contact value of the penetrant-matrix pair correlation function and the penetrant-matrix size ratio. For long time penetrant relaxation, in the relatively lower packing fraction metastable regime the local cage barriers are dominant and matrix collective elasticity effects unimportant. As packing fraction and/or penetrant size grows, much higher barriers emerge and the collective elasticity associated with the correlated matrix dynamic displacement that facilitates penetrant hopping becomes important. This results in a non-monotonic variation with packing fraction of the degree of decoupling between the matrix and penetrant alpha relaxation times. The conditions required for penetrant hopping to become slaved to the matrix alpha process are determined, which depend mainly on the penetrant to matrix particle size ratio. By analyzing the absolute and relative importance of the cage and elastic barriers we establish a mechanistic understanding of the origin of the predicted exponential growth of the penetrant hopping time with size ratio predicted at very high packing fractions. A dynamics-thermodynamics power law connection between the penetrant activation barrier and the matrix dimensionless compressibility is established as a prediction of theory, with different scaling exponents depending on whether matrix collective elasticity effects are important. Quantitative comparisons with simulations of the penetrant relaxation time, diffusion constant, and transient localization length of tracers in dense colloidal suspensions and cold viscous liquids reveal good agreements. Multiple new predictions are made that are testable via future experiments and simulations. Extension of the theoretical approach to more complex systems of high experimental interest (nonspherical molecules, semiflexible polymers, crosslinked networks) interacting via variable hard or soft repulsions and/or short range attractions is possible, including under external deformation.
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Affiliation(s)
- Baicheng Mei
- Department of Materials Science, University of Illinois, Urbana, IL 61801, USA. and Materials Research Laboratory, University of Illinois, Urbana, IL 61801, USA
| | - Kenneth S Schweizer
- Department of Materials Science, University of Illinois, Urbana, IL 61801, USA. and Materials Research Laboratory, University of Illinois, Urbana, IL 61801, USA and Department of Chemistry, University of Illinois, Urbana, IL 61801, USA and Department of Chemical & Biomolecular Engineering, University of Illinois, Urbana, IL 61801, USA
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10
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Phan AD, Zaccone A, Lam VD, Wakabayashi K. Theory of Pressure-Induced Rejuvenation and Strain Hardening in Metallic Glasses. PHYSICAL REVIEW LETTERS 2021; 126:025502. [PMID: 33512192 DOI: 10.1103/physrevlett.126.025502] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 12/11/2020] [Indexed: 06/12/2023]
Abstract
We theoretically investigate high-pressure effects on the atomic dynamics of metallic glasses. The theory predicts compression-induced rejuvenation and the resulting strain hardening that have been recently observed in metallic glasses. Structural relaxation under pressure is mainly governed by local cage dynamics. The external pressure restricts the dynamical constraints and slows down the atomic mobility. In addition, the compression induces a rejuvenated metastable state (local minimum) at a higher energy in the free-energy landscape. Thus, compressed metallic glasses can rejuvenate and the corresponding relaxation is reversible. This behavior leads to strain hardening in mechanical deformation experiments. Theoretical predictions agree well with experiments.
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Affiliation(s)
- Anh D Phan
- Faculty of Materials Science and Engineering, Computer Science, Artificial Intelligence Laboratory, Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam
- Department of Nanotechnology for Sustainable Energy, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - Alessio Zaccone
- Department of Physics "A. Pontremoli", University of Milan, via Celoria 16, 20133 Milano, Italy
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE Cambridge, United Kingdom
- Department of Chemical Engineering and Biotechnology, Statistical Physics Group, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, United Kingdom
| | - Vu D Lam
- Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam
| | - Katsunori Wakabayashi
- Department of Nanotechnology for Sustainable Energy, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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11
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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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12
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Ghosh A, Schweizer KS. Microscopic Theory of the Effect of Caging and Physical Bonding on Segmental Relaxation in Associating Copolymer Liquids. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00415] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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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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14
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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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15
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Müller N, Vogel M. Relation between concentration fluctuations and dynamical heterogeneities in binary glass-forming liquids: A molecular dynamics simulation study. J Chem Phys 2019; 150:064502. [DOI: 10.1063/1.5059355] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Niels Müller
- Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | - Michael Vogel
- Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany
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16
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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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17
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Phan AD, Schweizer KS. Elastically Collective Nonlinear Langevin Equation Theory of Glass-Forming Liquids: Transient Localization, Thermodynamic Mapping, and Cooperativity. J Phys Chem B 2018; 122:8451-8461. [DOI: 10.1021/acs.jpcb.8b04975] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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