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Nowok A, Grelska J, Dulski M, Szeremeta AZ, Łucak K, Jurkiewicz K, Hellwig H, Pawlus S. Normal-to-Supercooled Liquid Transition in Molecular Glass-Formers: A Hidden Structural Transformation Fuelled by Conformational Interconversion. J Phys Chem B 2024; 128:5055-5063. [PMID: 38726555 PMCID: PMC11129183 DOI: 10.1021/acs.jpcb.4c01025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 04/20/2024] [Accepted: 04/29/2024] [Indexed: 05/24/2024]
Abstract
Molecular dynamics and transport coefficients change significantly around the so-called Arrhenius crossover in glass-forming systems. In this article, we revisit the dynamic processes occurring in a glass-forming macrocyclic crown thiaether MeBzS2O above its glass transition, revealing two crossover temperatures: TB at 309 and TA at 333 K. We identify the second one as the Arrhenius crossover that is closely related to the normal-to-supercooled liquid transition in this compound. We show that the transformation occurring at this point goes far beyond molecular dynamics (where the temperature dependence of structural relaxation times changes its character from activation-like to super-Arrhenius), being reflected also in the internal structure and diffraction pattern. In this respect, we found a twofold local organization of the nearest-neighbor molecules via weak van der Waals forces, without the formation of any medium-range order or mesophases. The nearest surrounding of each molecule evolves structurally in time due to the ongoing fast conformational changes. We identify several conformers of MeBzS2O, demonstrating that its lowest-energy conformation is preferred mainly at lower temperatures, i.e., in the supercooled liquid state. Its increased prevalence modifies locally the short-range intermolecular order and promotes vitrification. Consequently, we indicate that the Arrhenius transition is fuelled rather by conformational changes in this glass-forming macrocyclic crown thiaether, which is a different scenario from the so-far existing concepts. Our studies combine broadband dielectric spectroscopy (BDS), X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations.
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Affiliation(s)
- Andrzej Nowok
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Stanisława Wyspiańskiego
27, 50-370 Wrocław, Poland
- Laboratoire
National des Champs Magnétiques Intenses, EMFL, CNRS UPR 3228, Université Toulouse, Université Toulouse
3, INSA-T, 31400 Toulouse,France
| | - Joanna Grelska
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Mateusz Dulski
- Faculty
of Science and Technology, Institute of
Materials Engineering, University of Silesia in Katowice, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland
| | - Anna Z. Szeremeta
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Kinga Łucak
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Karolina Jurkiewicz
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Hubert Hellwig
- Center
for Integrated Technology and Organic Synthesis (CiTOS), MolSys Research
Unit, University of Liège, B6a, Room 3/19, Allée du
Six Août 13, 4000 Liège, Belgium
| | - Sebastian Pawlus
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
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2
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Nowok A, Hellwig H, Dulski M, Książek M, Kusz J, Kuś P, Pawlus S. Revisiting Dynamic Processes and Relaxation Mechanisms in a Heterocyclic Glass-Former: Direct Observation of a Transient State. J Phys Chem B 2024; 128:1915-1926. [PMID: 38379513 PMCID: PMC10910497 DOI: 10.1021/acs.jpcb.3c06727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 01/10/2024] [Accepted: 02/07/2024] [Indexed: 02/22/2024]
Abstract
Despite decades of studies, a clear understanding of near-Tg phenomena remains challenging for glass-forming systems. This review delves into the intricate molecular dynamics of the small, heterocyclic thioether, 6-methyl-2,3-dihydro-1,4-benzodithiine (MeBzS2), with a particular focus on its near-Tg cold crystallization and relaxation mechanisms. Investigating isothermal crystallization kinetics at various temperatures reveals a significant interplay between its molecular dynamics and recrystallization from a supercooled liquid. We also identify two independent interconversion paths between energetically privileged conformers, characterized by strained transition states. We demonstrate that these spatial transformations induce substantial alterations in the dipole moment orientation and magnitude. Our investigation also extends to the complex salt PdCl2(MeBzS2), where we observe the transient conformers directly, revealing a direct relationship between their abundance and the local or macroscopic electric field. The initially energetically privileged isomers in an undisturbed system become less favored in the presence of an external electric field or ions, resulting even in an unexpected inversion of states. Consequently, we confirm the intramolecular character of secondary relaxation in MeBzS2 and its mechanism related to conformational changes within the heterocyclic ring. The research is based on the combination of broadband dielectric spectroscopy, X-ray diffraction, and quantum density functional theory calculations.
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Affiliation(s)
- Andrzej Nowok
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław 50-370, Poland
- Laboratoire
National des Champs Magnétiques Intenses, EMFL, CNRS UPR 3228,
Université Toulouse, Université
Toulouse 3, INSA-T, Toulouse 31400, France
| | - Hubert Hellwig
- Center
for Integrated Technology and Organic Synthesis (CiTOS), MolSys Research
Unit, University of Liège, B6a, Room 3/19, Allée Du
Six Août 13, Liège, Sart Tilman 4000, Belgium
| | - Mateusz Dulski
- Faculty
of Science and Technology, Institute of Materials Engineering, University of Silesia in Katowice, 75 Pułku Piechoty 1A, Chorzów 41-500, Poland
| | - Maria Książek
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Joachim Kusz
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
| | - Piotr Kuś
- Institute
of Chemistry, University of Silesia in Katowice, Szkolna 9, Katowice 40-003, Poland
| | - Sebastian Pawlus
- August
Chełkowski Institute of Physics, University
of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland
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Romanini M, Macovez R, Valenti S, Noor W, Tamarit JL. Dielectric Spectroscopy Studies of Conformational Relaxation Dynamics in Molecular Glass-Forming Liquids. Int J Mol Sci 2023; 24:17189. [PMID: 38139017 PMCID: PMC10743228 DOI: 10.3390/ijms242417189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/29/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
We review experimental results obtained with broadband dielectric spectroscopy concerning the relaxation times and activation energies of intramolecular conformational relaxation processes in small-molecule glass-formers. Such processes are due to the interconversion between different conformers of relatively flexible molecules, and generally involve conformational changes of flexible chain or ring moieties, or else the rigid rotation of planar groups, such as conjugated phenyl rings. Comparative analysis of molecules possessing the same (type of) functional group is carried out in order to test the possibility of assigning the dynamic conformational isomerism of given families of organic compounds to the motion of specific molecular subunits. These range from terminal halomethyl and acetyl/acetoxy groups to both rigid and flexible ring structures, such as the planar halobenzene cycles or the buckled saccharide and diazepine rings. A short section on polyesters provides a generalisation of these findings to synthetic macromolecules.
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Affiliation(s)
| | | | | | | | - Josep Lluís Tamarit
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Barcelona East School of Engineering (EEBE), Av. Eduard Maristany 10-14, E-08019 Barcelona, Spain; (M.R.); (R.M.); (S.V.); (W.N.)
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Hellwig H, Nowok A, Peksa P, Dulski M, Musioł R, Pawlus S, Kuś P. Molecular Dynamics and Near- Tg Phenomena of Cyclic Thioethers. Int J Mol Sci 2023; 24:17166. [PMID: 38138995 PMCID: PMC10742681 DOI: 10.3390/ijms242417166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/20/2023] [Accepted: 12/02/2023] [Indexed: 12/24/2023] Open
Abstract
This article presents the synthesis and molecular dynamics investigation of three novel cyclic thioethers: 2,3-(4'-methylbenzo)-1,4,7,10-tetrathiacyclododeca-2-ene (compound 1), 2,3,14,15-bis(4',4″(5″)-methylbenzo)-1,4,7,10,13,16,19,22,25-octathiacyclotetracosa-2,14-diene (compound 2), and 2,3,8,9-bis(4',4″(5″)-methylbenzo)-1,4,7,10-tetrathiacyclododeca-2,8-diene (compound 3). The compounds exhibit relatively high glass transition temperatures (Tg), which range between 254 and 283 K. This characteristic positions them within the so-far limited category of crown-like glass-formers. We demonstrate that cyclic thioethers may span both the realms of ordinary and sizeable molecular glass-formers, each featuring distinct physical properties. Furthermore, we show that the Tg follows a sublinear power law as a function of the molar mass within this class of compounds. We also reveal multiple dielectric relaxation processes of the novel cyclic thioethers. Above the Tg, their dielectric loss spectra are dominated by a structural relaxation, which originates from the cooperative reorientation of entire molecules and exhibits an excess wing on its high-frequency slope. This feature has been attributed to the Johari-Goldstein (JG) process. Each investigated compound exhibits also at least one intramolecular secondary non-JG relaxation stemming from conformational changes. Their activation energies range from approximately 19 kJ/mol to roughly 40 kJ/mol. Finally, we analyze the high-pressure molecular dynamics of compound 1, revealing a pressure-induced increase in its Tg with a dTg/dp coefficient equal to 197 ± 8 K/GPa.
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Affiliation(s)
- Hubert Hellwig
- Center for Integrated Technology and Organic Synthesis (CiTOS), MolSys Research Unit, University of Liège, B6a, Room 3/19, Allée du Six Août 13, 4000 Liege, Belgium;
| | - Andrzej Nowok
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Stanisława Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.N.); (P.P.)
| | - Paulina Peksa
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Stanisława Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.N.); (P.P.)
| | - Mateusz Dulski
- Faculty of Science and Technology, Institute of Materials Engineering, University of Silesia in Katowice, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland;
| | - Robert Musioł
- Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, 40-003 Katowice, Poland;
| | - Sebastian Pawlus
- August Chełkowski Institute of Physics, University of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland;
| | - Piotr Kuś
- Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, 40-003 Katowice, Poland;
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Valenti S, Arioli M, Jamett A, Tamarit JL, Puiggalí J, Macovez R. Amorphous solid dispersions of curcumin in a poly(ester amide): Antiplasticizing effect on the glass transition and macromolecular relaxation dynamics, and controlled release. Int J Pharm 2023; 644:123333. [PMID: 37597594 DOI: 10.1016/j.ijpharm.2023.123333] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 07/20/2023] [Accepted: 08/17/2023] [Indexed: 08/21/2023]
Abstract
In order to exploit the pharmacological potential of natural bioactive molecules with low water solubility, such as curcumin, it is necessary to develop formulations, such as amorphous polymer dispersions, which allow a constant release rate and at the same time avoid possible toxicity effects of the crystalline form of the molecule under scrutiny. In this study, polymer dispersions of curcumin were obtained in PADAS, a biodegradable semicrystalline copolymer based on 1,12-dodecanediol, sebacic acid and alanine. The dispersions were fully characterized by means of differential scanning calorimetry and broadband dielectric spectroscopy, and the drug release profile was measured in a simulated body fluid. Amorphous homogeneous binary dispersions were obtained for curcumin mass fraction between 30 and 50%. Curcumin has significantly higher glass transition temperature Tg (≈ 347 K) than the polymer matrix (≈274-277 K depending on the molecular weight), and dispersions displayed Tg's intermediate between those of the pure amorphous components, implying that curcumin acts as an effective antiplasticizer for PADAS. Dielectric spectroscopy was employed to assess the relaxation dynamics of the binary dispersion with 30 wt% curcumin, as well as that of each (amorphous) component separately. The binary dispersion was characterized by a single structural relaxation, a single Johari-Goldstein process, and two local intramolecular processes, one for each component. Interestingly, the latter processes scaled with the Tg of the sample, indicating that they are viscosity-sensitive. In addition, both the pristine polymer and the dispersion exhibited an interfacial Maxwell-Wagner relaxation, likely due to spatial heterogeneities associated with phase disproportionation in this polymer. The release of curcumin from the dispersion in a simulated body fluid followed a Fickian diffusion profile, and 51% of the initial curcumin content was released in 48 h.
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Affiliation(s)
- Sofia Valenti
- Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Synthetic Polymers: Structure and Properties. Biodegradable Polymers, Departament de Enginyeria Química, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Grup de Caracterització de Materials, Departament de Física, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain
| | - Matteo Arioli
- Synthetic Polymers: Structure and Properties. Biodegradable Polymers, Departament de Enginyeria Química, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain
| | - Alex Jamett
- Grup de Caracterització de Materials, Departament de Física, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain
| | - Josep Lluís Tamarit
- Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Grup de Caracterització de Materials, Departament de Física, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain
| | - Jordi Puiggalí
- Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Synthetic Polymers: Structure and Properties. Biodegradable Polymers, Departament de Enginyeria Química, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Carrer Baldiri i Reixac 11-15, E-08028 Barcelona, Catalonia, Spain
| | - Roberto Macovez
- Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain; Grup de Caracterització de Materials, Departament de Física, Universitat Politècnica de Catalunya, EEBE, Av. Eduard Maristany 10-14, E-08019 Barcelona, Catalonia, Spain.
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6
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Glass transition, crystallization kinetics, and inter-conformer relaxation dynamics of amorphous mitotane and related compounds. Int J Pharm 2022; 629:122390. [DOI: 10.1016/j.ijpharm.2022.122390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 11/14/2022]
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7
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Valenti S, Barrio M, Negrier P, Romanini M, Macovez R, Tamarit JL. Comparative Physical Study of Three Pharmaceutically Active Benzodiazepine Derivatives: Crystalline versus Amorphous State and Crystallization Tendency. Mol Pharm 2021; 18:1819-1832. [PMID: 33689364 PMCID: PMC8594866 DOI: 10.1021/acs.molpharmaceut.1c00081] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
![]()
Chemical derivatization and amorphization
are two possible strategies
to improve the solubility and bioavailability of drugs, which is a
key issue for the pharmaceutical industry. In this contribution, we
explore whether both strategies can be combined by studying how small
differences in the molecular structure of three related pharmaceutical
compounds affect their crystalline structure and melting point (Tm), the relaxation dynamics in the amorphous
phase, and the glass transition temperature (Tg), as well as the tendency toward recrystallization. Three
benzodiazepine derivatives of almost same molecular mass and structure
(Diazepam, Nordazepam and Tetrazepam) were chosen as model compounds.
Nordazepam is the only one that displays N–H···O
hydrogen bonds both in crystalline and amorphous phases, which leads
to a significantly higher Tm (by 70–80
K) and Tg (by 30–40 K) compared
to those of Tetrazepam and Diazepam (which display similar values
of characteristic temperatures). The relaxation dynamics in the amorphous
phase, as determined experimentally using broadband dielectric spectroscopy,
is dominated by a structural relaxation and a Johari–Goldstein
secondary relaxation, both of which scale with the reduced temperature T/Tg. The kinetic fragility
index is very low and virtually the same (mp ≈ 32) in all three compounds. Two more secondary relaxations
are observed in the glass state: the slower of the two has virtually
the same relaxation time and activation energy in all three compounds,
and is assigned to the inter-enantiomer conversion dynamics of the
flexible diazepine heterocycle between isoenergetic P and M conformations.
We tentatively assign the fastest secondary relaxation, present only
in Diazepam and Tetrazepam, to the rigid rotation of the fused diazepine–benzene
double ring relative to the six-membered carbon ring. Such motion
appears to be largely hindered in glassy Nordazepam, possibly due
to the presence of the hydrogen bonds. Supercooled liquid Tetrazepam
and Nordazepam are observed to crystallize into their stable crystalline
form with an Avrami exponent close to unity indicating unidimensional
growth with only sporadic nucleation, which allows a direct assessment
of the crystal growth rate. Despite the very similar growth mode,
the two derivatives exhibit very different kinetics for a fixed value
of the reduced temperature and thus of the structural relaxation time,
with Nordazepam displaying slower growth kinetics. Diazepam does not
instead display any tendency toward recrystallization over short periods
of time (even close to Tm). Both these
observations in three very similar diazepine derivatives provide direct
evidence that the kinetics of recrystallization of amorphous pharmaceuticals
is not a universal function, at least in the supercooled liquid phase,
of the structural or the conformational relaxation dynamics, and it
is not simply correlated with related parameters such as the kinetic
fragility or activation barrier of the structural relaxation. Only
the crystal growth rate, and not the nucleation rate, shows a correlation
with the presence or absence of hydrogen bonding.
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Affiliation(s)
- Sofia Valenti
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Maria Barrio
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Philippe Negrier
- Université Bordeaux, Laboratoire Ondes et Matière d'Aquitaine, UMR 5798, 351 Cours de la Libération, Talence F-33400, France
| | - Michela Romanini
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Roberto Macovez
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Josep-Lluis Tamarit
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
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