51
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Ingebrigtsen TS, Tanaka H. Effect of Size Polydispersity on the Nature of Lennard-Jones Liquids. J Phys Chem B 2015; 119:11052-62. [PMID: 26069998 DOI: 10.1021/acs.jpcb.5b02329] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polydisperse fluids are encountered everywhere in biological and industrial processes. These fluids naturally show a rich phenomenology exhibiting fractionation and shifts in critical point and freezing temperatures. We study here the effect of size polydispersity on the basic nature of Lennard-Jones (LJ) liquids, which represent most molecular liquids without hydrogen bonds, via two- and three-dimensional molecular dynamics computer simulations. A single-component liquid constituting spherical particles and interacting via the LJ potential is known to exhibit strong correlations between virial and potential energy equilibrium fluctuations at constant volume. This correlation significantly simplifies the physical description of the liquid, and these liquids are now known as Roskilde-simple (RS) liquids. We show that this simple nature of the single-component LJ liquid is preserved even for very high polydispersities (above 40% polydispersity for the studied uniform distribution). We also investigate isomorphs of moderately polydisperse LJ liquids. Isomorphs are curves in the phase diagram of RS liquids along which structure, dynamics, and some thermodynamic quantities are invariant in dimensionless units. We find that isomorphs are a good approximation even for polydisperse LJ liquids. The theory of isomorphs thus extends readily to size polydisperse fluids and can be used to improve even further the understanding of these intriguing systems.
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Affiliation(s)
- Trond S Ingebrigtsen
- Institute of Industrial Science, University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Hajime Tanaka
- Institute of Industrial Science, University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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52
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Saw S, Kamil SM, Dasgupta C. Spatial modulation of the composition of a binary liquid near a repulsive wall. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:052406. [PMID: 26066182 DOI: 10.1103/physreve.91.052406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Indexed: 06/04/2023]
Abstract
When a binary liquid is confined by a strongly repulsive wall, the local density is depleted near the wall and an interface similar to that between the liquid and its vapor is formed. This analogy suggests that the composition of the binary liquid near this interface should exhibit spatial modulation similar to that near a liquid-vapor interface even if the interactions of the wall with the two components of the liquid are the same. The Guggenheim adsorption relation quantifies the concentrations of two components of a binary mixture near a liquid-vapor interface and qualitatively states that the majority (minority) component enriches the interface for negative (positive) mixing energy if the surface tensions of the two components are not very different. From molecular dynamics simulations of binary mixtures with different compositions and interactions we find that the Guggenheim relation is qualitatively satisfied at wall-induced interfaces for systems with negative mixing energy at all state points considered. For systems with positive mixing energy, this relation is found to be qualitatively valid at low densities, while it is violated at state points with high density where correlations in the liquid are strong. This observation is validated by a calculation of the density profiles of the two components of the mixture using density functional theory with the Ramakrishnan-Yussouff free-energy functional. Possible reasons for the violation of the Guggenheim relation are discussed.
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Affiliation(s)
- Shibu Saw
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012, India
| | - S M Kamil
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012, India
- Department of Physics, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar 201314, India
| | - Chandan Dasgupta
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012, India
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53
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Harrach MF, Drossel B. Structure and dynamics of TIP3P, TIP4P, and TIP5P water near smooth and atomistic walls of different hydroaffinity. J Chem Phys 2015; 140:174501. [PMID: 24811640 DOI: 10.1063/1.4872239] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We perform molecular dynamics simulations to observe the structure and dynamics of water using different water models (TIP3P, TIP4P, TIP5P) at ambient conditions, constrained by planar walls, which are either modeled by smooth potentials or regular atomic lattices, imitating the honeycomb-structure of graphene. We implement walls of different hydroaffinity, different lattice constant, and different types of interaction with the water molecules. We find that in the hydrophobic regime the smooth wall generally represents a good abstraction of the atomically rough walls, while in the hydrophilic regime there are noticeable differences in structure and dynamics between all stages of wall roughness. For a small lattice constant however the smooth and the atomically rough wall still share a number of structural and dynamical similarities. Out of the three water models, TIP5P water shows the largest degree of tetrahedral ordering and is often the one that is least perturbed by the presence of the wall.
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Affiliation(s)
- Michael F Harrach
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - Barbara Drossel
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
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54
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Li L, Chen J, Deng W, Zhang C, Sha Y, Cheng Z, Xue G, Zhou D. Glass Transitions of Poly(methyl methacrylate) Confined in Nanopores: Conversion of Three- and Two-Layer Models. J Phys Chem B 2015; 119:5047-54. [DOI: 10.1021/jp511248q] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Linling Li
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Jiao Chen
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Weijia Deng
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Chen Zhang
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Ye Sha
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Zhen Cheng
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Gi Xue
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Dongshan Zhou
- Key
Laboratory of High Performance Polymer Materials and Technology of
Ministry of Education, Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, State Key Laboratory
of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China
- Xinjiang
Laboratory of Phase Transitions and Microstructures in Condensed Matters,
College of Physical Science and Technology, Yili Normal University, Yining 835000, P. R. China
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55
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56
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Hoang VV, Thoa DK, Odagaki T, Qui LN. Substrate effects on glass formation in simple monatomic supercooled liquids. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2014.11.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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57
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Dhotel A, Chen Z, Sun J, Youssef B, Saiter JM, Schönhals A, Tan L, Delbreilh L. From monomers to self-assembled monolayers: the evolution of molecular mobility with structural confinements. SOFT MATTER 2015; 11:719-731. [PMID: 25466448 DOI: 10.1039/c4sm01893a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effect of structural constriction on molecular mobility is investigated by broadband dielectric spectroscopy (BDS) within three types of molecular arrangements: monomers, oligomers and self-assembled monolayers (SAMs). While disordered monomers exhibit a variety of cooperative and local relaxation processes, the constrained nanodomains of oligomers and highly ordered structure of monolayers exhibit much hindered local molecular fluctuations. Particularly, in SAMs, motions of the silane headgroups are totally prevented whereas the polar endgroups forming the monolayer canopy show only one cooperative relaxation process. This latter molecular fluctuation is, for the first time, observed independently from other overlapping dielectric signals. Numerous electrostatic interactions among those dipolar endgroups are responsible for the strong cooperativity and heterogeneity of the canopy relaxation process. Our data analyses also revealed that the bulkiness of dipolar endgroups can disrupt the organization of the monolayer canopy thus increasing their ability to fluctuate as temperature is increased.
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Affiliation(s)
- Alexandre Dhotel
- AMME-LECAP, EA4528, International Lab., Av. de l'Université, B.P. 12, Normandie Univ. France, Université and INSA Rouen, 76801 Saint Etienne du Rouvray, France.
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58
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Harrach MF, Klameth F, Drossel B, Vogel M. Effect of the hydroaffinity and topology of pore walls on the structure and dynamics of confined water. J Chem Phys 2015; 142:034703. [DOI: 10.1063/1.4905557] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Michael F. Harrach
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - Felix Klameth
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - Barbara Drossel
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - Michael Vogel
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
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59
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Williams I, Oğuz EC, Bartlett P, Löwen H, Royall CP. Flexible confinement leads to multiple relaxation regimes in glassy colloidal liquids. J Chem Phys 2015; 142:024505. [PMID: 25591370 DOI: 10.1063/1.4905472] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Understanding relaxation of supercooled fluids is a major challenge and confining such systems can lead to bewildering behaviour. Here, we exploit an optically confined colloidal model system in which we use reduced pressure as a control parameter. The dynamics of the system are "Arrhenius" at low and moderate pressure, but at higher pressures relaxation is faster than expected. We associate this faster relaxation with a decrease in density adjacent to the confining boundary due to local ordering in the system enabled by the flexible wall.
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Affiliation(s)
- Ian Williams
- H.H. Wills Physics Laboratory, Tyndall Ave., Bristol BS8 1TL, United Kingdom
| | - Erdal C Oğuz
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Paul Bartlett
- School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Hartmut Löwen
- Institut für Theoretische Physik II, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| | - C Patrick Royall
- H.H. Wills Physics Laboratory, Tyndall Ave., Bristol BS8 1TL, United Kingdom
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60
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Rouha M, Cummings PT. Thickness-dependent structural arrangement in nano-confined imidazolium-based ionic liquid films. Phys Chem Chem Phys 2015; 17:4152-9. [DOI: 10.1039/c4cp05138f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nano-confined ionic liquid interfacial layers showing lateral and perpendicular structural changes dependent on thickness of adsorbed film.
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Affiliation(s)
- Michael Rouha
- Department of Chemical and Biomolecular Engineering
- Vanderbilt University
- Nashville
- USA
- Institute for Nanomaterials
| | - Peter T. Cummings
- Department of Chemical and Biomolecular Engineering
- Vanderbilt University
- Nashville
- USA
- Center for Nanophase Materials Sciences
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61
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Tong H, Xu N. Order parameter for structural heterogeneity in disordered solids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:010401. [PMID: 25122238 DOI: 10.1103/physreve.90.010401] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Indexed: 06/03/2023]
Abstract
We construct a structural order parameter from the energy equipartition of normal modes of vibration to quantify the structural heterogeneity in disordered solids. The order parameter exhibits strong spatial correlations with low-temperature dynamics and local structural entropy. To characterize the role of particles with the most defective local structures identified by the order parameter, we pin them and measure the system response. It turns out that particles with the largest value of the order parameter are responsible for the quasilocalized low-frequency vibration, instability, softening, and nonaffinity of disordered solids. The order parameter thus crucially links the heterogeneous structure to low-temperature dynamics and mechanical properties of disordered solids.
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Affiliation(s)
- Hua Tong
- CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Ning Xu
- CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
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62
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Ingebrigtsen TS, Dyre JC. The impact range for smooth wall-liquid interactions in nanoconfined liquids. SOFT MATTER 2014; 10:4324-31. [PMID: 24791276 DOI: 10.1039/c3sm52441h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Bulk and nanoconfined liquids have very different physics; for instance, nanoconfined liquids show stratification and position-dependent relaxation processes. A number of similarities between bulk and nanoconfined liquids have nevertheless been reported in computer simulations during the last decade. Inspired by these observations, we present results from molecular dynamics computer simulations of four nanoconfined liquids (the single-component Lennard-Jones liquid, the Kob-Andersen binary Lennard-Jones mixture, an asymmetric dumbbell model, and the Dzugutov liquid) demonstrating also a microscopic similarity between bulk and nanoconfined liquids. The results show that the interaction range for the wall-liquid and liquid-liquid interactions of the nanoconfined liquid is identical to that of the bulk liquid if the liquid is "Roskilde simple" in bulk as well as nanoconfinement, i.e., exhibits strong correlations between virial and potential-energy equilibrium fluctuations in the NVT ensemble. Under this condition, interactions beyond the first coordination shell may be ignored, in particular for the wall-liquid interactions. This is shown not to be the case for non-Roskilde-simple liquids.
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Affiliation(s)
- Trond S Ingebrigtsen
- DNRF Centre "Glass and Time", IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark.
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63
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Hanakata PZ, Douglas JF, Starr FW. Interfacial mobility scale determines the scale of collective motion and relaxation rate in polymer films. Nat Commun 2014; 5:4163. [DOI: 10.1038/ncomms5163] [Citation(s) in RCA: 182] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 05/20/2014] [Indexed: 11/10/2022] Open
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64
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Direct measurement of osmotic pressure via adaptive confinement of quasi hard disc colloids. Nat Commun 2014; 4:2555. [PMID: 24084759 DOI: 10.1038/ncomms3555] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 09/04/2013] [Indexed: 11/08/2022] Open
Abstract
Confining a system in a small volume profoundly alters its behaviour. Hitherto, attention has focused on static confinement where the confining wall is fixed such as in porous media. However, adaptive confinement where the wall responds to the interior has clear relevance in biological systems. Here we investigate this phenomenon with a colloidal system of quasi hard discs confined by a ring of particles trapped in holographic optical tweezers, which form a flexible elastic wall. This elasticity leads to quasi-isobaric conditions within the confined region. By measuring the displacement of the tweezed particles, we obtain the radial osmotic pressure. We further find a novel bistable state of a hexagonal structure and concentrically layered fluid mimicking the shape of the confinement. The hexagonal configurations are found at lower pressure than those of the fluid, thus the bistability is driven by the higher entropy of disordered arrangements, unlike bulk hard systems.
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65
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Klameth F, Henritzi P, Vogel M. Static and dynamic length scales in supercooled liquids: Insights from molecular dynamics simulations of water and tri-propylene oxide. J Chem Phys 2014; 140:144501. [DOI: 10.1063/1.4870089] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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66
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Williams I, Oğuz EC, Jack RL, Bartlett P, Löwen H, Royall CP. The effect of boundary adaptivity on hexagonal ordering and bistability in circularly confined quasi hard discs. J Chem Phys 2014; 140:104907. [PMID: 24628205 DOI: 10.1063/1.4867785] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the "strictness" of that wall.
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Affiliation(s)
- Ian Williams
- H.H. Wills Physics Laboratory, Tyndall Ave., Bristol BS8 1TL, United Kingdom
| | - Erdal C Oğuz
- Institut für Theoretische Physik II, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| | - Robert L Jack
- Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
| | - Paul Bartlett
- School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Hartmut Löwen
- Institut für Theoretische Physik II, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| | - C Patrick Royall
- H.H. Wills Physics Laboratory, Tyndall Ave., Bristol BS8 1TL, United Kingdom
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67
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Lang S, Franosch T, Schilling R. Structural quantities of quasi-two-dimensional fluids. J Chem Phys 2014; 140:104506. [DOI: 10.1063/1.4867284] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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68
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Anomalous Decoupling of Translational and Rotational Motion Under 1D Confinement, Evidences from Crystallization and Diffusion Experiments. ADVANCES IN DIELECTRICS 2014. [DOI: 10.1007/978-3-319-06100-9_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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69
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Ingebrigtsen TS, Errington JR, Truskett TM, Dyre JC. Predicting how nanoconfinement changes the relaxation time of a supercooled liquid. PHYSICAL REVIEW LETTERS 2013; 111:235901. [PMID: 24476293 DOI: 10.1103/physrevlett.111.235901] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Indexed: 05/13/2023]
Abstract
The properties of nanoconfined fluids can be strikingly different from those of bulk liquids. A basic unanswered question is whether the equilibrium and dynamic consequences of confinement are related to each other in a simple way. We study this question by simulation of a liquid comprising asymmetric dumbbell-shaped molecules, which can be deeply supercooled without crystallizing. We find that the dimensionless structural relaxation times-spanning six decades as a function of temperature, density, and degree of confinement-collapse when plotted versus excess entropy. The data also collapse when plotted versus excess isochoric heat capacity, a behavior consistent with the existence of isomorphs in the bulk and confined states.
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Affiliation(s)
- Trond S Ingebrigtsen
- DNRF Centre "Glass and Time," IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark
| | - Jeffrey R Errington
- Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA
| | - Thomas M Truskett
- McKetta Department of Chemical Engineering and Institute for Theoretical Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Jeppe C Dyre
- DNRF Centre "Glass and Time," IMFUFA, Department of Sciences, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark
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70
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Napolitano S, Capponi S, Vanroy B. Glassy dynamics of soft matter under 1D confinement: how irreversible adsorption affects molecular packing, mobility gradients and orientational polarization in thin films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:61. [PMID: 23797356 DOI: 10.1140/epje/i2013-13061-8] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/14/2013] [Accepted: 05/17/2013] [Indexed: 06/02/2023]
Abstract
The structural dynamics of polymers and simple liquids confined at the nanometer scale has been intensively investigated in the last two decades in order to test the validity of theories on the glass transition predicting a characteristic length scale of a few nanometers. Although this goal has not yet been reached, the anomalous behavior displayed by some systems--e.g. thin films of polystyrene exhibit reductions of Tg exceeding 70 K and a tremendous increase in the elastic modulus--has attracted a broad community of researchers, and provided astonishing advancement of both theoretical and experimental soft matter physics. 1D confinement is achieved in thin films, which are commonly treated as systems at thermodynamic equilibrium where free surfaces and solid interfaces introduce monotonous mobility gradients, extending for several molecular sizes. Limiting the discussion to finite-size and interfacial effects implies that film thickness and surface interactions should be sufficient to univocally determine the deviation from bulk behavior. On the contrary, such an oversimplified picture, although intuitive, cannot explain phenomena like the enhancement of segmental mobility in proximity of an adsorbing interface, or the presence of long-lasting metastable states in the liquid state. Based on our recent work, we propose a new picture on the dynamics of soft matter confined in ultrathin films, focusing on non-equilibrium and on the impact of irreversibly chain adsorption on the structural relaxation. We describe the enhancement of dynamics in terms of the excess in interfacial free volume, originating from packing frustration in the adsorbed layer (Guiselin brush) at t(*) ≪ 1, where t(*) is the ratio between the annealing time and the time scale of adsorption. Prolonged annealing at times exceeding the reptation time (usually t(*) ≫ 1 induces densification, and thus reduces the deviation from bulk behavior. In this Colloquium, after reviewing the experimental approaches permitting to investigate the structural relaxation of films with one, two or no free surfaces by means of dielectric spectroscopy, we propose several methods to determine gradients of mobility in thin films, and then discuss on the unexploited potential of analyses based on the time, temperature and thickness dependence of the orientational polarization via the dielectric strength.
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Affiliation(s)
- Simone Napolitano
- Laboratory of Polymer and Soft Matter Dynamics, Faculté des Sciences, Université Libre de Bruxelles, Boulevard du Triomphe, Bâtiment NO, 1050, Bruxelles, Belgium.
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71
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Klameth F, Vogel M. Structure and dynamics of supercooled water in neutral confinements. J Chem Phys 2013; 138:134503. [DOI: 10.1063/1.4798217] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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72
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Leocmach M, Russo J, Tanaka H. Importance of many-body correlations in glass transition: An example from polydisperse hard spheres. J Chem Phys 2013; 138:12A536. [DOI: 10.1063/1.4769981] [Citation(s) in RCA: 43] [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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73
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Gradenigo G, Trozzo R, Cavagna A, Grigera TS, Verrocchio P. Static correlations functions and domain walls in glass-forming liquids: The case of a sandwich geometry. J Chem Phys 2013; 138:12A509. [DOI: 10.1063/1.4771973] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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74
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Supercooled liquids with enhanced orientational order. Nat Commun 2012; 3:1233. [DOI: 10.1038/ncomms2228] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/26/2012] [Indexed: 11/08/2022] Open
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75
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Tanaka H. Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization: Bond orientational order in liquids. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:113. [PMID: 23104614 DOI: 10.1140/epje/i2012-12113-y] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 09/28/2012] [Indexed: 06/01/2023]
Abstract
There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed.
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Affiliation(s)
- Hajime Tanaka
- Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8505, Tokyo, Japan.
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76
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Spannuth M, Conrad JC. Confinement-induced solidification of colloid-polymer depletion mixtures. PHYSICAL REVIEW LETTERS 2012; 109:028301. [PMID: 23030210 DOI: 10.1103/physrevlett.109.028301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Indexed: 06/01/2023]
Abstract
Using a model colloid-polymer suspension, we show that confinement induces solidification in attractive colloidal suspensions via a fundamentally different route from that active in hard sphere colloidal suspensions. For a range of polymer concentrations, the suspensions undergo a phase transition from a colloidal fluid of clusters to a colloidal gel as confinement increases while polymer and particle concentration are held constant. In both fluid- and solidlike attractive suspensions, effects of confinement on the structure and dynamics appear at much larger thicknesses than for hard-sphere suspensions. The solidification does not originate from structuring of the colloids by the walls. Instead, by analyzing cluster size distributions in the fluid phase and particle dynamics in the gel phase as a function of confinement, we find that the strength of the effective interparticle attraction increases as the samples are confined. We show that the increase in the effective attraction can be understood as a consequence of the increasing importance of excluded volume due to the walls to the free energy of the polymer as confinement is increased.
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Affiliation(s)
- Melissa Spannuth
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, USA.
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77
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Berthier L, Kob W. Static point-to-set correlations in glass-forming liquids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:011102. [PMID: 22400507 DOI: 10.1103/physreve.85.011102] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Indexed: 05/31/2023]
Abstract
We analyze static point-to-set correlations in glass-forming liquids. The generic idea is to freeze the position of a set of particles in an equilibrium configuration and to perform sampling in the presence of this additional constraint. Qualitatively different geometries for the confining set of particles are considered and a detailed comparison of resulting static and dynamic correlation functions is performed. Our results reveal the existence of static spatial correlations not detected by conventional two-body correlators, which appear to be decoupled from, and shorter-ranged than, dynamical length scales characterizing dynamic heterogeneity. We find that the dynamics slows down dramatically under confinement, which suggests new ways to investigate the glass transition. Our results indicate that the geometry in which particles are randomly pinned is the best candidate to study static correlations.
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Affiliation(s)
- Ludovic Berthier
- Laboratoire Charles Coulomb, UMR 5221, CNRS and Université Montpellier 2, 34095 Montpellier, France
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78
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Mackowiak SA, Noble JM, Kaufman LJ. Manifestations of probe presence on probe dynamics in supercooled liquids. J Chem Phys 2011; 135:214503. [PMID: 22149798 DOI: 10.1063/1.3664125] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Experimental studies that follow behavior of single probes embedded in heterogeneous systems are increasingly common. The presence of probes may perturb the system, and such perturbations may or may not affect interpretation of host behavior from the probe observables typically measured. In this study, the manifestations of potential probe-induced changes to host dynamics in supercooled liquids are investigated via molecular dynamics simulations. It is found that probe dynamics do not necessarily mirror host dynamics as they exist either in the probe-free or probe-bearing systems. In particular, for a binary supercooled liquid, we find that smooth probes larger than the host particles induce increased translational diffusion in the host system; however, the diffusion is anisotropic and enhances caging of the probe, suppressing probe translational diffusion. This in turn may lead experiments that follow probe diffusion to suggest Stokes-Einstein behavior of the system even while both the probe-free and probe-bearing systems exhibit deviations from that behavior.
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79
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Pye JE, Roth CB. Two simultaneous mechanisms causing glass transition temperature reductions in high molecular weight freestanding polymer films as measured by transmission ellipsometry. PHYSICAL REVIEW LETTERS 2011; 107:235701. [PMID: 22182101 DOI: 10.1103/physrevlett.107.235701] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Indexed: 05/31/2023]
Abstract
We study the glass transition in confined polymer films and present the first experimental evidence indicating that two separate mechanisms can act simultaneously on the film to propagate enhanced mobility from the free surface into the material. Using transmission ellipsometry, we have measured the thermal expansion of ultrathin, high molecular-weight (MW), freestanding polystyrene films over an extended temperature range. For two different MWs, we observed two distinct reduced glass transition temperatures (T(g)'s), separated by up to 60 K, within single films with thicknesses h less than 70 nm. The lower transition follows the expected MW dependent, linear T(g)(h) behavior previously seen in high MW freestanding films. We also observe a much stronger upper transition with no MW dependence that exhibits the same T(g)(h) dependence as supported and low MW freestanding polymer films.
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Affiliation(s)
- Justin E Pye
- Department of Physics, Emory University, Atlanta, Georgia 30322, USA
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