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Körber T, Pötzschner B, Krohn F, Rössler EA. Reorientational dynamics in highly asymmetric binary low-molecular mixtures-A quantitative comparison of dielectric and NMR spectroscopy results. J Chem Phys 2021; 155:024504. [PMID: 34266265 DOI: 10.1063/5.0056838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Previously, we scrutinized the dielectric spectra of a binary glass former made by a low-molecular high-Tg component 2-(m-tertbutylphenyl)-2'-tertbutyl-9,9'-spirobi[9H]fluorene (m-TPTS; Tg = 350 K) and low-Tg tripropyl phosphate (TPP; Tg = 134 K) [Körber et al., Phys. Chem. Chem. Phys. 23, 7200 (2021)]. Here, we analyze nuclear magnetic resonance (NMR) spectra and stimulated echo decays of deuterated m-TPTS-d4 (2H) and TPP (31P) and attempt to understand the dielectric spectra in terms of component specific dynamics. The high-Tg component (α1) shows relaxation similar to that of neat systems, yet with some broadening upon mixing. This correlates with high-frequency broadening of the dielectric spectra. The low-Tg component (α2) exhibits highly stretched relaxations and strong dynamic heterogeneities indicated by "two-phase" spectra, reflecting varying fractions of fast and slow liquid-like reorienting molecules. Missing for the high-Tg component, such two-phase spectra are identified down to wTPP = 0.04, indicating that isotropic reorientation prevails in the rigid high-Tg matrix stretching from close to Tg TPP to Tg1 wTPP. This correlates with low-frequency broadening of the dielectric spectra. Two Tg values are defined: Tg1 (wTPP) displays a plasticizer effect, whereas Tg2 (wTPP) passes through a maximum, signaling extreme separation of the component dynamics at low wTPP. We suggest understanding the latter counter-intuitive feature by referring to a crossover from "single glass" to "double glass" scenario revealed by recent MD simulations. Analyses reveal that a second population of TPP molecules exists, which is associated with the dynamics of the high-Tg component. However, the fractions are lower than suggested by the dielectric spectra. We discuss this discrepancy considering the role of collective dynamics probed by dielectric but not by NMR spectroscopy.
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Affiliation(s)
- Thomas Körber
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
| | - Björn Pötzschner
- 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
| | - Ernst A Rössler
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
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Körber T, Krohn F, Neuber C, Schmidt HW, Rössler EA. Reorientational dynamics of highly asymmetric binary non-polymeric mixtures – a dielectric spectroscopy study. Phys Chem Chem Phys 2021; 23:7200-7212. [DOI: 10.1039/d0cp06652d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two separated relaxations α1 and α2 with different temperature dependences are identified in the mixtures. They are attributed to the dynamics associated with the high-Tg (α1) and the low-Tg component (α2) with distinct Tg concentration dependences.
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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
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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.
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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.
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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 .
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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.
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Gambino T, Alegría A, Arbe A, Colmenero J, Malicki N, Dronet S, Schnell B, Lohstroh W, Nemkovski K. Applying Polymer Blend Dynamics Concepts to a Simplified Industrial System. A Combined Effort by Dielectric Spectroscopy and Neutron Scattering. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b00881] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas Gambino
- Centro
de Física
de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Manufacture Française
des Pneumatiques MICHELIN, Site de Ladoux, 23 place des Carmes Déchaux, Cedex 9 F-63040, Clermont-Ferrand, France
| | - Angel Alegría
- Centro
de Física
de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, E-20080 San Sebastián, Spain
| | - Arantxa Arbe
- Centro
de Física
de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Juan Colmenero
- Centro
de Física
de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, E-20080 San Sebastián, Spain
- Donostia International
Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
| | - Nicolas Malicki
- Manufacture Française
des Pneumatiques MICHELIN, Site de Ladoux, 23 place des Carmes Déchaux, Cedex 9 F-63040, Clermont-Ferrand, France
| | - Séverin Dronet
- Manufacture Française
des Pneumatiques MICHELIN, Site de Ladoux, 23 place des Carmes Déchaux, Cedex 9 F-63040, Clermont-Ferrand, France
| | - Benoît Schnell
- Manufacture Française
des Pneumatiques MICHELIN, Site de Ladoux, 23 place des Carmes Déchaux, Cedex 9 F-63040, Clermont-Ferrand, France
| | - Wiebke Lohstroh
- Heinz Maier-Leibnitz Zentrum, Technische Universität München, Lichtenbergstraße 1, D-85748 Garching, Germany
| | - Kirill Nemkovski
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
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