1
|
Flämig M, Gabrielyan L, Minikejew R, Markarian S, Rössler EA. Dielectric relaxation and proton field-cycling NMR relaxometry study of dimethyl sulfoxide/glycerol mixtures down to glass-forming temperatures. Phys Chem Chem Phys 2020; 22:9014-9028. [PMID: 32293628 DOI: 10.1039/d0cp00501k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mixtures of glycerol and dimethyl sulfoxide (DMSO) are studied by dielectric spectroscopy (DS) and by 1H field-cycling (FC) NMR relaxometry in the entire concentration range and down to glass-forming temperatures (170-323 K). Molecular dynamics is accessed for 0 < xDMSO ≤ 0.64, at higher concentration phase separation occurs. The FC technique provides the frequency dependence of the spin-lattice relaxation rate which is transformed to the susceptibility representation and thus allows comparing NMR and DS results. The DS spectra virtually do not change with xDMSO and T, only the relaxation times become shorter. This is in contrast to the non-associated mixture toluene/quinaldine for which strong spectral changes occur. The FC relaxation spectra of glycerol in solution with DMSO or (deuterated) DMSO-d6 display a bimodal structure with a high-frequency part reflecting rotational and a low-frequency part reflecting translational dynamics. Regarding the rotational contribution in the glycerol/DMSO-d6 mixtures, no spectral change with xDMSO and T is observed. Yet, the non-deuterated mixture reveals a broader relaxation spectrum. Time constants τrot(T) probed by the two techniques complement each, a range 10-11 s < τ < 10 s is covered. The glass transition temperature Tg(xDMSO) is determined, yielding Tg = 149.5 ± 1 K of pure DMSO by extrapolation. Analysing the low-frequency FC NMR spectra allows to determine the diffusion coefficient Dtrans. Its logarithm shows a linear xDMSO-dependence as does lg τrot. The ratio Dtrans/Drot is independent of xDMSO and its low value indicates large separation of translation and rotation. The corresponding unphysically small hydrodynamic radius indicates strong failure of Stokes-Einstein-Debye relation. Such anomaly is taken as characteristics of a 3d hydrogen-bonded network. We conclude, although DMSO is an aprotic liquid the molecule is continuously incorporated in the hydrogen network of glycerol. Both molecules display common dynamics, i.e., no decoupling of the component dynamics is found in contrast to quinaldine/toluene with a similar Tg difference of its components.
Collapse
Affiliation(s)
- Max Flämig
- Nordbayerisches NMR-Zentrum, Universität Bayreuth, 95440 Bayreuth, Germany.
| | - Liana Gabrielyan
- Chair of Physical Chemistry, Yerevan State University, 0025 Yerevan, Armenia
| | - Rafael Minikejew
- Nordbayerisches NMR-Zentrum, Universität Bayreuth, 95440 Bayreuth, Germany.
| | - Shiraz Markarian
- Chair of Physical Chemistry, Yerevan State University, 0025 Yerevan, Armenia
| | - Ernst A Rössler
- Nordbayerisches NMR-Zentrum, Universität Bayreuth, 95440 Bayreuth, Germany.
| |
Collapse
|
2
|
Körber T, Krohn F, Neuber C, Schmidt HW, Rössler EA. Main and secondary relaxations of non-polymeric high-T g glass formers as revealed by dielectric spectroscopy. Phys Chem Chem Phys 2020; 22:9086-9097. [PMID: 32300764 DOI: 10.1039/d0cp00930j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of high-Tg glass formers with Tg values varying between 347 and 390 K and molar masses in the range of 341 and 504 g mol-1 are investigated by dielectric spectroscopy. They are compared to paradigmatic reference systems. Differently polar side groups are attached to a rigid non-polar core unit at different positions. Thereby, the dielectric relaxation strength varies over more than two decades. All the relaxation features typical of molecular glass formers are rediscovered, i.e. stretching of the main (α-) relaxation, a more or less pronounced secondary (β-) process, and a fragility index quite similar to that of other molecular systems. The position of the polar nitrile side group influences the manifestation of the β-relaxation. The α-relaxation stretching displays the trend to become less with higher relaxation strength Δεα, confirming recent reports. Typical for a generic β-process is the increase of its amplitude above Tg, which is found to follow a power-law behaviour as a function of the ratio τα/τβ with a universal exponent; yet, its relative amplitude to that of the α-relaxation varies as does the temporal separation of both processes. The mean activation energy of the β-process as well as the width of the energy distribution gβ(E) increases more or less systematically with Tg. The latter is determined from the dielectric spectra subjected to a scaling procedure assuming a thermally activated process. Plotting gβ(E) as a function of the reduced energy scale E/Tg, the distributions are centred between 19-35 and their widths differ by a factor 2-3.
Collapse
Affiliation(s)
- Thomas Körber
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany.
| | - Felix Krohn
- Department of Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, 95440 Bayreuth, Germany
| | - Christian Neuber
- Department of Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, 95440 Bayreuth, Germany
| | - Hans-Werner Schmidt
- Department of Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, 95440 Bayreuth, Germany
| | - Ernst A Rössler
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany.
| |
Collapse
|
3
|
Körber T, Minikejew R, Pötzschner B, Bock D, Rössler EA. Dynamically asymmetric binary glass formers studied by dielectric and NMR spectroscopy. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:143. [PMID: 31773406 DOI: 10.1140/epje/i2019-11909-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/16/2019] [Indexed: 06/10/2023]
Abstract
We investigate the component dynamics in asymmetric binary glass formers. Focusing on the dielectric spectra of the high-Tg components m-tricresyl phosphate and quinaldine mixed with toluene as low-Tg component, the broadend spectra cannot be described by Kohlrausch or Cole-Davidson (CD) functions. Instead, we apply a generalized CD function which allows to control the width of the susceptibility independently of its high-frequency flank. The spectra show a common broadening and failure of the frequency-temperature superposition with increasing toluene concentration. This is confirmed by stimulated echo experiments showing an increased stretching of the probed orientational correlation function. In analogy to the definition of Tg, we consider "isodynamic points". For each component, a different but linear concentration dependence of 1/Tiso is revealed, indicating different time scales. Qualitativly, we do not find significant differences for the present mixtures with Tg-contrasts of 63-89K compared to those with larger Tg-contrast ( [Formula: see text] K): Whereas the high-Tg component shows relaxation features similar to those of neat glass formers, yet, with "atypical" weak relaxation broadening, the faster low-Tg component displays pronounced dynamic heterogeneities. This is supported by scrutinizing NMR relaxation data of several mixtures investigated previously as a function of concentration. A universal evolution of the dynamics of the high-Tg as well as the low-Tg component is suggested for mixtures with high [Formula: see text]Tg .
Collapse
Affiliation(s)
- Th Körber
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - R Minikejew
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - B Pötzschner
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - D Bock
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - E A Rössler
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany.
| |
Collapse
|
4
|
Caporaletti F, Capaccioli S, Valenti S, Mikolasek M, Chumakov AI, Monaco G. A microscopic look at the Johari-Goldstein relaxation in a hydrogen-bonded glass-former. Sci Rep 2019; 9:14319. [PMID: 31586113 PMCID: PMC6778113 DOI: 10.1038/s41598-019-50824-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 09/03/2019] [Indexed: 11/23/2022] Open
Abstract
Understanding the glass transition requires getting the picture of the dynamical processes that intervene in it. Glass-forming liquids show a characteristic decoupling of relaxation processes when they are cooled down towards the glassy state. The faster (βJG) process is still under scrutiny, and its full explanation necessitates information at the microscopic scale. To this aim, nuclear γ-resonance time-domain interferometry (TDI) has been utilized to investigate 5-methyl-2-hexanol, a hydrogen-bonded liquid with a pronounced βJG process as measured by dielectric spectroscopy. TDI probes in fact the center-of-mass, molecular dynamics at scattering-vectors corresponding to both inter- and intra-molecular distances. Our measurements demonstrate that, in the undercooled liquid phase, the βJG relaxation can be visualized as a spatially-restricted rearrangement of molecules within the cage of their closest neighbours accompanied by larger excursions which reach out at least the inter-molecular scale and are related to cage-breaking events. In-cage rattling and cage-breaking processes therefore coexist in the βJG relaxation.
Collapse
Affiliation(s)
- F Caporaletti
- Dipartimento di Fisica, Università di Trento, I-38123, Povo, Trento, Italy.
| | - S Capaccioli
- Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, I-56127, Pisa, Italy
- CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127, Pisa, Italy
| | - S Valenti
- Grup de Caracterització de Materials, Department of Physics, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019, Barcelona, Spain
| | - M Mikolasek
- ESRF-The European Synchrotron, CS40 220, 38043, Grenoble, Cedex 9, France
| | - A I Chumakov
- ESRF-The European Synchrotron, CS40 220, 38043, Grenoble, Cedex 9, France
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | - G Monaco
- Dipartimento di Fisica, Università di Trento, I-38123, Povo, Trento, Italy.
| |
Collapse
|
5
|
Pötzschner B, Mohamed F, Bächer C, Wagner E, Lichtinger A, Bock D, Kreger K, Schmidt HW, Rössler EA. Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy. J Chem Phys 2018; 146:164504. [PMID: 28456197 DOI: 10.1063/1.4980085] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one finds indications that the β2-process starts to disintegrate. More and more TPP molecules get immobilized upon decreasing cTPP. We conclude that the β-process is a cooperative process.
Collapse
Affiliation(s)
- B Pötzschner
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - F Mohamed
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - C Bächer
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - E Wagner
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - A Lichtinger
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - D Bock
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - K Kreger
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - H-W Schmidt
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| | - E A Rössler
- Experimentalphysik II, University of Bayreuth, 95447 Bayreuth, Germany and Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth, Germany
| |
Collapse
|
6
|
Yu HB, Richert R, Samwer K. Structural rearrangements governing Johari-Goldstein relaxations in metallic glasses. SCIENCE ADVANCES 2017; 3:e1701577. [PMID: 29159283 PMCID: PMC5693560 DOI: 10.1126/sciadv.1701577] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 10/20/2017] [Indexed: 05/10/2023]
Abstract
The Johari-Goldstein secondary (β) relaxations are an intrinsic feature of supercooled liquids and glasses. They are crucial to many properties of glassy materials, but the underlying mechanisms are still not established. In a model metallic glass, we study the atomic rearrangements by molecular dynamics simulations at time scales of up to microseconds. We find that the distributions of single-particle displacements exhibit multiple peaks, whose positions quantitatively match the pair distribution function. These are identified as the structural signature of cooperative string-like excitations. Furthermore, the most probable time of the string-like motions coincides with the β-relaxation time as probed by dynamical mechanical simulations over a wide temperature range and is consistent with a theoretical model. Our results provide insights into the long-standing puzzle regarding the structural origin of β relaxations in glassy metallic materials.
Collapse
Affiliation(s)
- Hai-Bin Yu
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 Hubei, China
- Corresponding author. (H.-B.Y.); (R.R.); (K.S.)
| | - Ranko Richert
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
- Corresponding author. (H.-B.Y.); (R.R.); (K.S.)
| | - Konrad Samwer
- I. Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany
- Corresponding author. (H.-B.Y.); (R.R.); (K.S.)
| |
Collapse
|
7
|
Fragiadakis D, Roland CM. Participation in the Johari–Goldstein Process: Molecular Liquids versus Polymers. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b00621] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D. Fragiadakis
- Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375-5342, United States
| | - C. M. Roland
- Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375-5342, United States
| |
Collapse
|
8
|
Körber T, Mohamed F, Hofmann M, Lichtinger A, Willner L, Rössler EA. The Nature of Secondary Relaxations: The Case of Poly(ethylene-alt-propylene) Studied by Dielectric and Deuteron NMR Spectroscopy. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02536] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Thomas Körber
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Fathia Mohamed
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Marius Hofmann
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Anne Lichtinger
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Lutz Willner
- Institute
of Complex Systems, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Ernst A. Rössler
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| |
Collapse
|
9
|
Wang M, Li X, Guo Y, Wu T, Liu YD, Ngai KL, Wang LM. A new secondary relaxation in the rigid and planar 1-methylindole: Evidence from binary mixture studies. J Chem Phys 2016; 145:214501. [DOI: 10.1063/1.4968564] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Meng Wang
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| | - Xiangqian Li
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| | - Yuxing Guo
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| | - Tao Wu
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| | - Ying Dan Liu
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| | - K. L. Ngai
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
- CNR-IPCF, Largo B. Pontecorvo 3, Pisa I-56127, Italy
| | - Li-Min Wang
- State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
| |
Collapse
|
10
|
Pötzschner B, Mohamed F, Lichtinger A, Bock D, Rössler EA. Dynamics of asymmetric non-polymeric binary glass formers—A nuclear magnetic resonance and dielectric spectroscopy study. J Chem Phys 2015; 143:154506. [DOI: 10.1063/1.4932981] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- B. Pötzschner
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - F. Mohamed
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - A. Lichtinger
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - D. Bock
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - E. A. Rössler
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| |
Collapse
|
11
|
Mohamed F, Hofmann M, Pötzschner B, Fatkullin N, Rössler EA. Dynamics of PPI Dendrimers: A Study by Dielectric and 2H NMR Spectroscopy and by Field-Cycling 1H NMR Relaxometry. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00486] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- F. Mohamed
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - M. Hofmann
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - B. Pötzschner
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - N. Fatkullin
- Institute
of Physics, Kazan Federal University, Kazan 420008, Tatarstan Russia
| | - E. A. Rössler
- Experimentalphysik
II, Universität Bayreuth, 95440 Bayreuth, Germany
| |
Collapse
|
12
|
Abstract
Abstract
Focusing on metallic glasses as model systems, we review the features and mechanisms of the β-relaxations, which are intrinsic and universal to supercooled liquids and glasses, and demonstrate their importance in understanding many crucial unresolved issues in glassy physics and materials science, including glass transition phenomena, mechanical properties, shear-banding dynamics and deformation mechanisms, diffusion and the breakdown of the Stokes–Einstein relation as well as crystallization and stability of glasses. We illustrate that it is an attractive prospect to incorporate these insights into the design of new glassy materials with extraordinary properties. We also outline important questions regarding the nature of β-relaxations and highlight some emerging research directions in this still-evolving field.
Collapse
Affiliation(s)
- Hai Bin Yu
- Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany
| | - Wei Hua Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hai Yang Bai
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Konrad Samwer
- Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany
| |
Collapse
|
13
|
Bock D, Kahlau R, Pötzschner B, Körber T, Wagner E, Rössler EA. Dynamics of asymmetric binary glass formers. II. Results from nuclear magnetic resonance spectroscopy. J Chem Phys 2014; 140:094505. [DOI: 10.1063/1.4865945] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
14
|
Kahlau R, Dörfler T, Rössler EA. Secondary relaxations in a series of organic phosphate glasses revealed by dielectric spectroscopy. J Chem Phys 2013; 139:134504. [DOI: 10.1063/1.4822002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
15
|
Bock D, Kahlau R, Micko B, Pötzschner B, Schneider GJ, Rössler EA. On the cooperative nature of the β-process in neat and binary glasses: a dielectric and nuclear magnetic resonance spectroscopy study. J Chem Phys 2013; 139:064508. [PMID: 23947872 DOI: 10.1063/1.4816374] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
By means of dielectric as well as (2)H and (31)P nuclear magnetic resonance spectroscopy (NMR) the component dynamics of the binary glass tripropyl phosphate (TPP)/polystyrene (PS/PS-d3) is selectively investigated for concentrations distributed over the full range. We study the secondary (β-) relaxation below T(g), which is found in all investigated samples containing TPP, but not in neat polystyrene. The dielectric spectrum of the β-process is described by an asymmetric distribution of activation energies, essentially not changing in the entire concentration regime; its most probable value is E/k ≅ 24 T(g). Persistence of the β-process is confirmed by (31)P NMR Hahn-echo and spin-lattice relaxation experiments on TPP, which identify the nature of the β-process as being highly spatially hindered as found for other (neat) glasses studied previously, or re-investigated within this work. The corresponding (2)H NMR experiments on PS-d3 confirm the absence of a β-process in neat PS-d3, but reveal a clear signature of a β-process in the mixture, i.e., polystyrene monomers perform essentially the same type of secondary relaxation as the TPP molecules. Yet, there are indications that some fractions of PS-d3 as well as TPP molecules become immobilized in the mixture in contrast to the case of neat glasses. We conclude that in a binary glass the β-process introduced by one component induces a highly similar motion in the second component, and this may be taken as an indication of its cooperative nature.
Collapse
Affiliation(s)
- D Bock
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | | | | | | | | | | |
Collapse
|