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Single molecule demonstration of Debye-Stokes-Einstein breakdown in polystyrene near the glass transition temperature. Nat Commun 2022; 13:3580. [PMID: 35739122 PMCID: PMC9226357 DOI: 10.1038/s41467-022-31318-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 06/10/2022] [Indexed: 11/25/2022] Open
Abstract
Rotational-translational decoupling, in which translational motion is apparently enhanced over rotational motion in violation of Stokes-Einstein (SE) and Debye-Stokes-Einstein (DSE) predictions, has been observed in materials near their glass transition temperatures (Tg). This has been posited to result from ensemble averaging in the context of dynamic heterogeneity. In this work, ensemble and single molecule experiments are performed in parallel on a fluorescent probe in high molecular weight polystyrene near its Tg. Ensemble results show decoupling onset at approximately 1.15Tg, increasing to over three orders of magnitude at Tg. Single molecule measurements also show a high degree of decoupling, with typical molecules at Tg showing translational diffusion coefficients nearly 400 times higher than expected from SE/DSE predictions. At the single molecule level, higher degree of breakdown is associated with particularly mobile molecules and anisotropic trajectories, providing support for anomalous diffusion as a critical driver of rotational-translational decoupling and SE/DSE breakdown. Experiments with high-molecular-weight polystyrene provide insights into the mechanisms behind rotational-translational decoupling in glassy systems. Specifically, particularly mobile molecules exhibiting anisotropic trajectories are found to play a key role in Debye-Stokes-Einstein breakdown.
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Berthier L. Self-Induced Heterogeneity in Deeply Supercooled Liquids. PHYSICAL REVIEW LETTERS 2021; 127:088002. [PMID: 34477435 DOI: 10.1103/physrevlett.127.088002] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 07/29/2021] [Indexed: 06/13/2023]
Abstract
A theoretical treatment of deeply supercooled liquids is difficult because their properties emerge from spatial inhomogeneities that are self-induced, transient, and nanoscopic. I use computer simulations to analyze self-induced static and dynamic heterogeneity in equilibrium systems approaching the experimental glass transition. I characterize the broad sample-to-sample fluctuations of salient dynamic and thermodynamic properties in elementary mesoscopic systems. Findings regarding local lifetimes and distributions of dynamic heterogeneity are in excellent agreement with recent single molecule studies. Surprisingly broad thermodynamic fluctuations are also found, which correlate well with dynamic fluctuations, thus providing a local test of the thermodynamic origin of slow dynamics.
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Affiliation(s)
- Ludovic Berthier
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France and Yusuf Hamied Deprtment of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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Zhang G, Rocha S, Lu G, Yuan H, Uji-i H, Floudas GA, Müllen K, Xiao L, Hofkens J, Debroye E. Spatially and Temporally Resolved Heterogeneities in a Miscible Polymer Blend. ACS OMEGA 2020; 5:23931-23939. [PMID: 32984713 PMCID: PMC7513360 DOI: 10.1021/acsomega.0c03173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 08/25/2020] [Indexed: 06/11/2023]
Abstract
Mapping the spatial and temporal heterogeneities in miscible polymer blends is critical for understanding and further improving their material properties. However, a complete picture on the heterogeneous dynamics is often obscured in ensemble measurements. Herein, the spatial and temporal heterogeneities in fully miscible polystyrene/oligostyrene blend films are investigated by monitoring the rotational diffusion of embedded individual probe molecules using defocused wide-field fluorescence microscopy. In the same blend film, three significantly different types of dynamical behaviors (referred to as modes) of the probe molecules can be observed at the same time, namely, immobile, continuously rotating, and intermittently rotating probe molecules. This reveals a prominent spatial heterogeneity in local dynamics at the nanometer scale. In addition to that, temporal heterogeneity is uncovered by the nonexponential characteristic of the rotational autocorrelation functions of single-molecule probes. Moreover, the occurrence probabilities of these different modes strongly depend on the polystyrene: oligostyrene ratios in the blend films. Remarkably, some probe molecules switch between the continuous and intermittent rotational modes at elevated temperature, indicating a possible alteration in local dynamics that is triggered by the dynamic heterogeneity in the blends. Although some of these findings can be discussed by the self-concentration model and the results provided by ensemble averaging techniques (e.g., dielectric spectroscopy), there are implications that go beyond current models of blend dynamics.
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Affiliation(s)
- Guofeng Zhang
- State
Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute
of Laser Spectroscopy, Collaborative Innovation Center of Extreme
Optics, Shanxi University, Taiyuan, 030006, China
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
| | - Susana Rocha
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
| | - Gang Lu
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
- Institute
of Advanced Materials & Key Laboratory of Flexible Electronics, Nanjing Tech University, Nanjing 211816, China
| | - Haifeng Yuan
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
| | - Hiroshi Uji-i
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
- Research
Institute for Electronic Science (RIES), Hokkaido University, N20W10, Sapporo City 001-0020, Japan
| | - George A. Floudas
- Department
of Physics, University of Ioannina, GR-45110 Ioannina, Greece
- Max
Plank Institute for Polymer Research, Mainz D-55128, Germany
| | - Klaus Müllen
- Max
Plank Institute for Polymer Research, Mainz D-55128, Germany
| | - Liantuan Xiao
- State
Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute
of Laser Spectroscopy, Collaborative Innovation Center of Extreme
Optics, Shanxi University, Taiyuan, 030006, China
| | - Johan Hofkens
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
- Max
Plank Institute for Polymer Research, Mainz D-55128, Germany
| | - Elke Debroye
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
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Xie SJ, Schweizer KS. Microscopic Theory of Dynamically Heterogeneous Activated Relaxation as the Origin of Decoupling of Segmental and Chain Relaxation in Supercooled Polymer Melts. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00849] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Shi-Jie Xie
- Departments of Materials Science, University of Illinois, Urbana, Illinois 61801, United States
- Material Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
- Center for Membrane Separation and Water Science & Technology, Ocean College, Zhejiang University of Technology, Hangzhou 310014, PR China
| | - Kenneth S. Schweizer
- Departments of Materials Science, University of Illinois, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
- Material Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
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5
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Xie SJ, Schweizer KS. A collective elastic fluctuation mechanism for decoupling and stretched relaxation in glassy colloidal and molecular liquids. J Chem Phys 2020; 152:034502. [DOI: 10.1063/1.5129550] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Shi-Jie Xie
- Department of Materials Science, University of Illinois, Urbana, Illinois 61801, USA
- Material Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
- Center for Membrane Separation and Water Science and Technology, Ocean College, Zhejiang University of Technology, Hangzhou 310014, People’s Republic of China
| | - Kenneth S. Schweizer
- Department of Materials Science, University of Illinois, Urbana, Illinois 61801, USA
- Material Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA
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Manz AS, Aly M, Kaufman LJ. Correlating fragility and heterogeneous dynamics in polystyrene through single molecule studies. J Chem Phys 2019; 151:084501. [PMID: 31470706 DOI: 10.1063/1.5114905] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Many macroscopic properties of polymers depend on their molecular weight, with one notable example being glass transition temperature: polymers with higher molecular weights typically have higher glass transition temperatures than their lower molecular weight polymeric and oligomeric counterparts. Polymeric systems close to their glass transition temperatures also exhibit interesting properties, showing both high (and molecular weight dependent) fragility and strong evidence of dynamic heterogeneity. While studies have detailed the correlations between molecular weight and fragility, studies clearly detailing correlations between molecular weight and degree of heterogeneous dynamics are lacking. In this study, we use single molecule rotational measurements to investigate the impact of molecular weight on polystyrene's degree of heterogeneity near its glass transition temperature. To this end, two types of fluorescent probes are embedded in films composed of polystyrene ranging from 0.6 to 1364.0 kg mol-1. We find correlation between polystyrene molecular weight, fragility, and degree of dynamic heterogeneity as reported by single molecule stretching exponents but do not find clear correlation between these quantities and time scales associated with dynamic exchange.
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Affiliation(s)
- Alyssa S Manz
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Mariam Aly
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Laura J Kaufman
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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Ray S, Chauvier A, Walter NG. Kinetics coming into focus: single-molecule microscopy of riboswitch dynamics. RNA Biol 2018; 16:1077-1085. [PMID: 30328748 DOI: 10.1080/15476286.2018.1536594] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Riboswitches are dynamic RNA motifs that are mostly embedded in the 5'-untranslated regions of bacterial mRNAs, where they regulate gene expression transcriptionally or translationally by undergoing conformational changes upon binding of a small metabolite or ion. Due to the small size of typical ligands, relatively little free energy is available from ligand binding to overcome the often high energetic barrier of reshaping RNA structure. Instead, most riboswitches appear to take advantage of the directional and hierarchical folding of RNA by employing the ligand as a structural 'linchpin' to adjust the kinetic partitioning between alternate folds. In this model, even small, local structural and kinetic effects of ligand binding can cascade into global RNA conformational changes affecting gene expression. Single-molecule (SM) microscopy tools are uniquely suited to study such kinetically controlled RNA folding since they avoid the ensemble averaging of bulk techniques that loses sight of unsynchronized, transient, and/or multi-state kinetic behavior. This review summarizes how SM methods have begun to unravel riboswitch-mediated gene regulation.
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Affiliation(s)
- Sujay Ray
- a Single Molecule Analysis Group, Department of Chemistry, University of Michigan , Ann Arbor , MI , USA
| | - Adrien Chauvier
- a Single Molecule Analysis Group, Department of Chemistry, University of Michigan , Ann Arbor , MI , USA
| | - Nils G Walter
- a Single Molecule Analysis Group, Department of Chemistry, University of Michigan , Ann Arbor , MI , USA
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