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Srinivasan H, Sharma VK, García Sakai V, Mitra S. Nature of Subdiffusion Crossover in Molecular and Polymeric Glassformers. PHYSICAL REVIEW LETTERS 2024; 132:058202. [PMID: 38364148 DOI: 10.1103/physrevlett.132.058202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 11/21/2023] [Accepted: 01/03/2024] [Indexed: 02/18/2024]
Abstract
A crossover from a non-Gaussian to Gaussian subdiffusion has been observed ubiquitously in various polymeric and molecular glassformers. We have developed a framework that generalizes the fractional Brownian motion model to incorporate non-Gaussian features by introducing a jump kernel. We illustrate that the non-Gaussian fractional Brownian motion model accurately characterizes the subdiffusion crossover. From the solutions of the non-Gaussian fractional Brownian motion model, we gain insights into the nature of van Hove self-correlation in non-Gaussian subdiffusive regime, which is found to exhibit exponential tails, providing first such experimental evidence in molecular glassformers. The validity of the model is supported by comparison with incoherent quasielastic neutron scattering data obtained from several molecular and polymeric glassformers.
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Affiliation(s)
- H Srinivasan
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - V García Sakai
- ISIS Neutron and Muon Centre, Rutherford Appleton Laboratory, Didcot, United Kingdom
| | - S Mitra
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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Hashimoto S, Yamaguchi S, Harada M, Nakajima K, Kikuchi T, Ohishi K. Anomalous behavior of liquid molecules near solid nanoparticles: Novel interpretation on thermal conductivity enhancement in nanofluids. J Colloid Interface Sci 2023; 638:475-486. [PMID: 36764243 DOI: 10.1016/j.jcis.2023.01.101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 01/16/2023] [Accepted: 01/20/2023] [Indexed: 02/05/2023]
Abstract
HYPOTHESIS Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities. EXPERIMENTS The behavior of liquid molecules in nanofluids containing SiO2 particles larger than 100 nm, which were dispersed in a 50 wt% aqueous solution of ethylene glycol, was investigated by means of small-angle neutron scattering, quasi-elastic neutron scattering, wide-angle X-ray scattering, and Raman spectroscopy. FINDINGS The vibrational changes in the liquid molecules caused by the interactions between the nanoparticles and liquid molecules surrounding the nanoparticles contributed majorly to the increase in the thermal conductivity values of the SiO2 nanofluids. Because the vibration of liquid molecules is equivalent to phonon conduction in solids, the increase in thermal conductivity of the suspension due to the presence of nanoparticles was inferred to be derived from the limitation of the translational diffusion, which induces a solid-like behavior in the liquid.
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Affiliation(s)
- Shunsuke Hashimoto
- Energy Management Research-Domain, Emerging Technology Division, Toyota Central R&D Labs., Inc., 1-1, Yokomichi, Nagakute, Aichi 480-1192, Japan.
| | - Satoshi Yamaguchi
- Analysis Research-Domain, Emerging Technology Division, Toyota Central R&D Labs., Inc., 1-1, Yokomichi, Nagakute, Aichi 480-1192, Japan
| | - Masashi Harada
- Analysis Research-Domain, Emerging Technology Division, Toyota Central R&D Labs., Inc., 1-1, Yokomichi, Nagakute, Aichi 480-1192, Japan
| | - Kenji Nakajima
- Materials & Life Science Division, Japan Proton Accelerator Research Complex (J-PARC) Center, 2-4, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
| | - Tatsuya Kikuchi
- Materials & Life Science Division, Japan Proton Accelerator Research Complex (J-PARC) Center, 2-4, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
| | - Kazuki Ohishi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science & Society (CROSS), 162-1, Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
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Hashimoto S, Nakajima K, Kikuchi T, Kamazawa K, Shibata K, Yamada T. Experimental analysis on dynamics of liquid molecules adjacent to particles in nanofluids. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Khairy Y, Alvarez F, Arbe A, Colmenero J. Disentangling Self-Atomic Motions in Polyisobutylene by Molecular Dynamics Simulations. Polymers (Basel) 2021; 13:polym13040670. [PMID: 33672368 PMCID: PMC7927061 DOI: 10.3390/polym13040670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/08/2021] [Accepted: 02/17/2021] [Indexed: 01/16/2023] Open
Abstract
We present fully atomistic molecular dynamics simulations on polyisobutylene (PIB) in a wide temperature range above the glass transition. The cell is validated by direct comparison of magnitudes computed from the simulation and measured by neutron scattering on protonated samples reported in previous works. Once the reliability of the simulation is assured, we exploit the information in the atomic trajectories to characterize the dynamics of the different kinds of atoms in PIB. All of them, including main-chain carbons, show a crossover from Gaussian to non-Gaussian behavior in the intermediate scattering function that can be described in terms of the anomalous jump diffusion model. The full characterization of the methyl-group hydrogen motions requires accounting for rotational motions. We show that the usually assumed statistically independence of rotational and segmental motions fails in this case. We apply the rotational rate distribution model to correlation functions calculated for the relative positions of methyl-group hydrogens with respect to the carbon atom at which they are linked. The contributions to the vibrational density of states are also discussed. We conclude that methyl-group rotations are coupled with the main-chain dynamics. Finally, we revise in the light of the simulations the hypothesis and conclusions made in previously reported neutron scattering investigations on protonated samples trying to address the origin of the dielectric β-process.
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Affiliation(s)
- Yasmin Khairy
- Physics Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt;
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
| | - Fernando Alvarez
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain
| | - Arantxa Arbe
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Juan Colmenero
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
- Correspondence:
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Busselez R, Lefort R, Ghoufi A, Beuneu B, Frick B, Affouard F, Morineau D. The non-Gaussian dynamics of glycerol. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:505102. [PMID: 22051524 DOI: 10.1088/0953-8984/23/50/505102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have combined incoherent quasielastic neutron scattering experiments and atomistic molecular simulations to investigate the microscopic dynamics of glycerol moving away from the hydrodynamic limit. We relate changes in the momentum transfer (Q) dependence of the relaxation time to distinct changes of the single-particle dynamics. Going from small to large values of Q, a first crossover at about 0.5 Å(-1) is related to the coupling of the translational diffusion dynamics to the non-Debye structural relaxation, while the second crossover at a Q-value near the main diffraction peak is associated with the Gaussian to non-Gaussian crossover of the short-time molecular dynamics, related to the decaging processes. We offer an unprecedented extension of previous studies on polymeric systems towards the case of the typical low-molecular-weight glass-forming system glycerol.
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Affiliation(s)
- R Busselez
- Institute of Physics of Rennes, CNRS-University of Rennes 1, UMR 6251, F-35042 Rennes, France
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Prisk TR, Tyagi M, Sokol PE. Dynamics of small-molecule glass formers confined in nanopores. J Chem Phys 2011; 134:114506. [DOI: 10.1063/1.3560039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Swenson J, Sjöström J, Fernandez-Alonso F. Reduced mobility of di-propylene glycol methylether in its aqueous mixtures by quasielastic neutron scattering. J Chem Phys 2010; 133:234506. [PMID: 21186874 DOI: 10.1063/1.3515958] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogen (H-) bonding interplay between water and other organic molecules is important both in nature and in a wide range of technological applications. Structural relaxation and, thus, diffusion in aqueous mixtures are generally dependent on both the strength and the structure of the H-bonds. To investigate diffusion in H-bonding mixtures, we present a quasielastic neutron scattering study of di-propylene glycol methylether (2PGME) mixed with H(2)O (or D(2)O) over the concentration range 0-90 wt.% water. We observe a nonmonotonic behavior of the dynamics with a maximum in average relaxation time for the mixture with 30 wt.% water, which is more than a factor 2 larger compared to that of either of the pure constituents. This is a result in qualitative agreement with previous calorimetric studies and the behavior of aqueous mixtures of simple mono-alcohols. More surprisingly, we notice that the dynamics of the 2PGME molecules in the mixture is slowed down by more than a factor 3 at 30 wt.% water but that the water dynamics indicates an almost monotonous behavior. Furthermore, in the low momentum transfer (Q) range of the 2PGME, where the intermediate scattering function I(Q,t) is considerably stretched in time (i.e., the stretching parameter β ≪ 1), it is evident for the 2PGME-D(2)O samples that the Q-dependence of the inverse average relaxation time, <τ>(-1), is greater than 2. This implies that the relaxation dynamics is partly homogenously stretched, i.e., the relaxation of each relaxing unit is somewhat intrinsically stretched in time.
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Affiliation(s)
- Jan Swenson
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Göteborg, Sweden
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Busselez R, Lefort R, Guendouz M, Frick B, Merdrignac-Conanec O, Morineau D. Molecular dynamics of glycerol and glycerol-trehalose bioprotectant solutions nanoconfined in porous silicon. J Chem Phys 2009; 130:214502. [DOI: 10.1063/1.3147222] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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