Article
Polymer Science
Carlo Andrea Massa, Francesco Puosi, Dino Leporini
Summary: Extensive molecular-dynamics simulations were used to study a polymer model exhibiting heterogeneous Johari-Goldstein secondary relaxation. The time-temperature-pressure superposition of the primary relaxation was confirmed. The time scales of the primary and JG relaxations were found to be highly correlated, in agreement with the predictions of the Coupling Model. However, the exponent of the power law deviated from the expected value, potentially due to the specific relaxation process and the heterogeneity of the JG process.
Article
Multidisciplinary Sciences
Kumpei Shiraishi, Hideyuki Mizuno, Atsushi Ikeda
Summary: Supercooled liquids with complicated structural relaxation processes have been a long-standing problem in condensed matter physics. Previous experiments observed that relaxation dynamics in many molecular liquids separate into two distinct processes at low temperatures. This study uses molecular dynamics simulations to investigate the potential energy landscape and provides the first direct evidence of the topographic hierarchy that induces relaxation. The results contribute to a fundamental and comprehensive understanding of relaxation dynamics in supercooled liquids.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Materials Science, Multidisciplinary
Liang Gao, Yang Sun, Hai-Bin Yu
Summary: The Johari-Goldstein secondary (0) relaxations are intrinsic features of supercooled liquids and glasses, and play a crucial role in several properties of glassy materials. This study demonstrates through atomistic simulations and percolation analysis that the mobile clusters are percolated at the occurrence of 0 relaxation in seven different glassy systems. The percolation transition shows the same temperature and time dependence with 0 relaxation, and emerges universally when about 10% of the atoms are mobile, with a dimension of approximately 2 for the system-spanning cluster. These findings contribute to the understanding of 0 relaxation in glasses.
Article
Multidisciplinary Sciences
Michela Romanini, Roberto Macovez, Maria Barrio, Josep Lluis Tamarit
Summary: Temperature- and pressure-dependent dielectric spectroscopy and calorimetry techniques were used to characterize benzophenone and its ortho-bromobenzophenone derivative in the liquid and glass states. The study revealed the existence of a Johari-Goldstein relaxation in both compounds and identified the mechanism of intramolecular relaxation.
SCIENTIFIC REPORTS
(2021)
Article
Biochemistry & Molecular Biology
Antonio Tripodo, Francesco Puosi, Marco Malvaldi, Dino Leporini
Summary: Research indicates that analysis based on mutual information provides a deeper insight into the transport and relaxation properties of molecular and macromolecular glass formers. Near the glass transition, mutual information reveals different mobility and relaxation properties of particle clusters with filamentous or compact globular structures, especially in the context of dynamical heterogeneity and secondary Johari-Goldstein relaxation processes. Both dynamical heterogeneity and mutual information between orientation and bond displacement reach local maxima at the time scales of primary and JG secondary relaxation, indicating the involvement of rotation/translation coupling in the mechanistic explanation of both phenomena in (macro)molecular systems.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2021)
Article
Biochemistry & Molecular Biology
Sofia Valenti, Luis Javier del Valle, Michela Romanini, Meritxell Mitjana, Jordi Puiggali, Josep Lluis Tamarit, Roberto Macovez
Summary: In this study, dispersions of a small-molecule drug in biodegradable polylactide were investigated using differential scanning calorimetry and broadband dielectric spectroscopy. The study reveals that the same small-molecule compound can have opposite effects on the mobility of a biopolymer depending on the preparation method, temperature, and polymer enantiomerism. The drug acts as an antiplasticizer for films but as a plasticizer for microfibres. Furthermore, the structural relaxation time of the samples is influenced by the chemical composition and morphology.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Physics, Fluids & Plasmas
K. L. Ngai
Summary: This study focuses on the research status and techniques related to JG beta relaxation in glass-forming materials. By combining TDI technique with dielectric and neutron scattering data analysis, it reveals that the JG beta relaxation is heterogeneous and comprises processes with different length scales, with processes of longer length scale having longer relaxation time. The study also finds that the primitive relaxation time of the coupling model falls within the distribution of the TDI q-dependent JG beta-relaxation times, which explains the experimental observations of the relationship between tau(beta) and tau(0) in various glass formers.
Article
Chemistry, Physical
N. N. Ren, P. F. Guan, K. L. Ngai
Summary: This study investigated the superposition of frequency dispersion of structural alpha relaxation at different temperature and pressure combinations, as well as the time dependence of faster processes like caged molecule dynamics and JG beta relaxation. Through molecular dynamics simulations, it was confirmed that this property holds for not only alpha relaxation but also caged dynamics and JG beta relaxation.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Federico Caporaletti, Simone Capaccioli, Dimitrios Bessas, Aleksander I. Chumakov, Alessandro Martinelli, Giulio Monaco
Summary: The JG relaxation is closely connected to the structural relaxation in supercooled liquids, and investigating its microscopic properties is crucial for understanding the glass-transition. In this study, we used time-domain interferometry to probe the microscopic density fluctuations of the van der Waals glass-former cumene. Our results show that the molecules involved in the JG relaxation undergo a restricted motion, leading to local cage-breaking events at the characteristic time-scale for molecular re-orientations.
JOURNAL OF MOLECULAR LIQUIDS
(2023)
Article
Chemistry, Physical
Hao Zhang, Xinyi Wang, Hai-Bin Yu, Jack F. Douglas
Summary: Through simulations, a direct correspondence between the JG beta-relaxation process and the lifetime of mobile particle clusters was discovered in metallic glass-forming materials, with the relaxation being dominated by smaller atomic species. This relationship sheds light on the dynamics of structural relaxation in glass-forming materials at low temperatures.
EUROPEAN PHYSICAL JOURNAL E
(2021)
Article
Polymer Science
Herminio P. Diogo, Joaquim J. Moura Ramos
Summary: This study investigates the molecular mobility of poly (ether imide) across a wide temperature range using thermostimulated depolarization currents, covering the amorphous solid state, glass transition, and rubber state. Through analyzing different motional modes of the PEI glass transition, a comprehensive view of physical aging process was achieved. Additionally, a new mobility mode was identified below T-g and space charge motions were found in the rubber state.
JOURNAL OF APPLIED POLYMER SCIENCE
(2022)
Article
Mathematics, Applied
Zeric Njitacke Tabekoueng, Sishu Shankar Muni, Theophile Fonzin Fozin, Gervais Dolvis Leutcho, Jan Awrejcewicz
Summary: This contribution investigates the phenomenon of hidden heterogeneous extreme multistability in coupled neurons. The study reveals that the heterogeneous neuron system can exhibit coexistence of an infinite number of electrical activities involving both periodic and chaotic patterns. A noninvasive control method is applied to suppress the periodic coexisting activities, leaving only the desired chaotic one.
Article
Polymer Science
Dominic Wadkin-Snaith, Paul Mulheran, Karen Johnston
Summary: This study used molecular dynamics simulations to investigate the nucleation and crystallization of polymers under homogeneous and heterogeneous conditions. The presence of a surface was found to affect the crystallization behavior of the polymers. Polymers with stiff chains crystallized more readily than flexible polymers in the absence of a surface, while the presence of an isotropic surface promoted crystallization in flexible systems. The model provides insight into the mechanisms of polymer crystallization and can help in the design of nucleants for controlling polymer crystallization.
Article
Mathematics, Applied
Bukyoung Jhun, Hoyun Choi
Summary: This study explores the effectiveness of different vaccination strategies in reducing mortality rates during epidemics. The fatality-based strategy is more effective when contagion rates are high and vaccine supply is low, while the contact-based strategy performs better with sufficient vaccine supply. Combining these two strategies does not effectively reduce the number of deaths, and similar phenomena occur in other epidemics.
Article
Mechanics
N. Moreno, M. Ellero
Summary: This work presents a methodology for conducting rheological studies on smoothed dissipative particle dynamics under arbitrary flow configurations. It evaluates the accuracy and flexibility of the method through viscometric studies on Newtonian fluids in various flow conditions, and demonstrates its applicability in obtaining viscoelastic properties of non-Newtonian fluids. The new computational approach offers significant advantages in a range of applications, from multiscale simulations to characterizing complex flows.
Article
Physics, Condensed Matter
C. A. Massa, D. Leporini, F. Puosi
JOURNAL OF PHYSICS-CONDENSED MATTER
(2020)
Article
Polymer Science
Antonio Tripodo, Francesco Puosi, Marco Malvaldi, Simone Capaccioli, Dino Leporini
Article
Multidisciplinary Sciences
Andrea Giuntoli, Francesco Puosi, Dino Leporini, Francis Starr, Jack F. Douglas
Article
Materials Science, Multidisciplinary
F. Puosi, F. Fidecaro, S. Capaccioli, D. Pisignano, D. Leporini
Article
Polymer Science
Carlo Andrea Massa, Francesco Puosi, Antonio Tripodo, Dino Leporini
Summary: The vibrational dynamics of a model polymer glass is studied using Molecular Dynamics simulations, focusing on the soft monomers and their tendency to form quasi-local clusters with strong anisotropy in shape. Limited size systems were used to better understand the role of these soft monomers.
Article
Biochemistry & Molecular Biology
Antonio Tripodo, Francesco Puosi, Marco Malvaldi, Dino Leporini
Summary: Research indicates that analysis based on mutual information provides a deeper insight into the transport and relaxation properties of molecular and macromolecular glass formers. Near the glass transition, mutual information reveals different mobility and relaxation properties of particle clusters with filamentous or compact globular structures, especially in the context of dynamical heterogeneity and secondary Johari-Goldstein relaxation processes. Both dynamical heterogeneity and mutual information between orientation and bond displacement reach local maxima at the time scales of primary and JG secondary relaxation, indicating the involvement of rotation/translation coupling in the mechanistic explanation of both phenomena in (macro)molecular systems.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2021)
Article
Biochemistry & Molecular Biology
Gianfranco Cordella, Antonio Tripodo, Francesco Puosi, Dario Pisignano, Dino Leporini
Summary: This paper examines the nanoscale surface instability of ultrathin molecular films deposited on a substrate under uniaxial compression using molecular dynamics simulations. The study reveals the development of one-dimensional wrinkling structures and the scaling relationship between wavelength and film length. It is found that small compressions can be well described, while large compressions lead to increased wrinkling amplitudes with nearly constant cross sections, offering a novel interpretation of instability. These findings may be crucial for designing effective wrinkling and buckling patterns in flexible platforms for electronics and photonics.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2021)
Article
Biochemistry & Molecular Biology
Antonio Tripodo, Gianfranco Cordella, Francesco Puosi, Marco Malvaldi, Dino Leporini
Summary: This article introduces two neural networks for predicting particle mobility in molecular glassformers and compares their performance. It is found that the prediction accuracy of neural network A is higher, tentatively attributed to better consideration of bond reorientation. Both neural networks exhibit impressive and comparable performance in predicting the dynamic heterogeneity of the system.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Polymer Science
Carlo Andrea Massa, Francesco Puosi, Dino Leporini
Summary: Extensive molecular-dynamics simulations were used to study a polymer model exhibiting heterogeneous Johari-Goldstein secondary relaxation. The time-temperature-pressure superposition of the primary relaxation was confirmed. The time scales of the primary and JG relaxations were found to be highly correlated, in agreement with the predictions of the Coupling Model. However, the exponent of the power law deviated from the expected value, potentially due to the specific relaxation process and the heterogeneity of the JG process.
Article
Polymer Science
Sharon Carol Volpe, Dino Leporini, Francesco Puosi
Summary: Using molecular dynamics simulations, we study the structure and mechanical response of a porous glassy system derived from phase separation of a model polymer melt. We find that coarsening dynamics control the slow structural evolution, while the mechanical response exhibits low values for Young's and shear modulus due to the porous structure. Large deformations result in intermittent stress-strain curves with avalanches of plastic events. This work extends previous numerical studies by considering the role of chain connectivity in the elastic and plastic responses of porous materials.
Article
Materials Science, Multidisciplinary
Gianfranco Cordella, Francesco Puosi, Antonio Tripodo, Dino Leporini, Anael Lemaitre
Summary: Surface morphogenesis in compressed thin films may result from spatially correlated plastic activity. This phenomenon has been overlooked in the past, but should be highly prevalent for compressed glassy thin films.
PHYSICAL REVIEW MATERIALS
(2022)
Review
Physics, Atomic, Molecular & Chemical
Vasile Bercu, Carlo Andrea Massa, Silvia Pizzanelli, Luca Pardi, Dino Leporini, Massimo Martinelli
APPLIED MAGNETIC RESONANCE
(2020)
Article
Physics, Multidisciplinary
F. Puosi, F. Fidecaro, S. Capaccioli, D. Pisignano, D. Leporini
PHYSICAL REVIEW RESEARCH
(2019)
Article
Chemistry, Physical
Antonio Tripodo, Andrea Giuntoli, Marco Malvaldi, Dino Leporini
