Article
Physics, Fluids & Plasmas
Luana S. Moreira, Douglas D. de Vargas, Mateus H. Kohler
Summary: The introduction of flexibility in water force fields during molecular dynamics simulations of nanoconfined water has a significant impact on viscosity, diffusion, and dipole orientation. The level of confinement and the choice of force-field family greatly influence the behavior of water molecules in nanoconfined systems.
Article
Physics, Fluids & Plasmas
Luana S. Moreira, Douglas D. de Vargas, Mateus H. Koehler
Summary: This study investigates the effects of introducing flexibility in water force fields on molecular dynamics simulations of nanoconfined water. The results show that viscosity, diffusion, and dipole orientation are greatly influenced by the flexibility and the family of force fields used.
Article
Engineering, Chemical
Sidath Wijesinghe, Dvora Perahia, Ting Ge, K. Michael Salerno, Gary S. Grest
Summary: The stress relaxation of branched polymers, especially the impact of branch length compared to the entanglement length of linear polymer, plays a crucial role in viscosity modification. Shorter branch lengths relax within the entanglement time, affecting chain mobility and stress relaxation by increasing tube diameter and friction coefficient, essentially acting as a solvent in the system.
Article
Chemistry, Physical
Jinseong Kim, Jun Mo Kim, Chunggi Baig
Summary: In a narrowly confined two-dimensional melt system, the stiffness of ring polymers increases, leading to an overall extended interpenetrated chain configuration. Compared to 3D systems, 2D ring and linear melts exhibit relatively similar structural and dynamical properties due to similar chain structures, less effective chain ends, and absence of complex topological constraints.
Article
Chemistry, Physical
Raja Azhar Ashraaf Khan, Hang-Kai Qi, Jian-Hua Huang, Meng-Bo Luo
Summary: The effect of nanoparticle size on the glass transition temperature of polymer nanocomposites shows a complex behavior, with T-g decaying almost exponentially at low nanoparticle volume fractions and exhibiting a more varied pattern at high volume fractions. The decrease in T-g is attributed to reduced adsorbed polymer monomers, while the increase is linked to slower diffusion of larger nanoparticles. The diffusion constant and relaxation time of polymer chains are closely related to T-g behavior.
Article
Polymer Science
Yexin Zheng, Mesfin Tsige, Shi-Qing Wang
Summary: In this study, molecular dynamics simulations were used to investigate the entanglement lockup phenomena in the uniaxial melt stretching of entangled polymer melts. The results revealed that under high strains, the entanglement network became increasingly tighter, leading to chain tension and the formation of network junctions. It was hypothesized that the interchain entanglement at junctions can lockup as long as certain conditions are met. This study provides insights into the mechanical properties of polymer materials.
MACROMOLECULAR RAPID COMMUNICATIONS
(2023)
Article
Polymer Science
Jianshe Xia, Julia Ann Kalow, Monica Olvera de la Cruz
Summary: This study investigates the topological structural changes, microscopic dynamics, and linear rheology of unentangled vitrimers through molecular dynamics simulations. The results show minor variations in topological structure with temperature and increased dynamic heterogeneities near the topological freezing transition temperature. The simulation results are quantitatively consistent with predictions from the sticky Rouse model.
Article
Polymer Science
Yaguang Sun, Kaiwei Wan, Wenhui Shen, Jianxin He, Tong Zhou, Hui Wang, Hua Yang, Xinghua Shi
Summary: Recycling and reprocessing of conventional thermosetting polymers have gained attention due to environmental concerns. This study focuses on covalent adaptable networks (CANs) which incorporate functional groups capable of reversible exchange reactions into polymer networks, altering the topology arrangement and achieving stress relaxation. The researchers developed a machine-learning force field to describe the exchange reactions of polyimine CANs and provided insights into reaction mechanisms and energy profiles through enhanced sampling methods.
Article
Polymer Science
Yijing Nie, Jun Yang, Zongfa Liu, Zhiping Zhou, Yongqiang Ming, Tongfan Hao
Summary: Based on molecular dynamics simulations, this study focused on the stretch-induced precursor formation and nucleation process in carbon nanotube (CNT) filled polyethylene. It was found that CNTs can orient polymer segments along the stretching direction, leading to higher degree of orientation and higher content of special conformational segments in the interfacial regions.
Article
Physics, Multidisciplinary
Elena N. Govorun, Ruslan M. Shupanov, Sophia A. Pavlenko, Alexei R. Khokhlov
Summary: The paper discusses the use of conformation-dependent design of polymer sequences to control macromolecular self-assembly, considering different microphase-separated morphologies. It explores the application of this design in domains of different shapes through probability distributions and exponential asymptotes.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Polymer Science
Emmanuel N. Skountzos, Katerina S. Karadima, Vlasis G. Mavrantzas
Summary: The study investigates the impact of adsorbed domains and nanoparticle bridging chains on the properties of attractive polymer nanocomposite melts through MD simulations. The presence of adsorbed polymer significantly affects the dynamic and conformational properties of the nanocomposite, especially under conditions favoring higher surface-to-volume ratios. Moreover, the bridging chains drive the formation of a nanoparticle network which becomes denser and stronger with increasing concentration of the polymer matrix in nanoparticles.
Article
Chemistry, Physical
Margherita Mele, Roberto Covino, Raffaello Potestio
Summary: This study addresses the problem of coarsening the conformational space of proteins in molecular dynamics simulations. Using an information-theoretical framework, the researchers identified the optimal resolution level that balances simplicity and informativeness, and discovered that clustering methods inducing an ultrametric structure in the low-resolution space are the most physically accurate. The proposed strategy has applicability beyond computational biophysics and can be a valuable tool for extracting useful information from large datasets.
Article
Mechanics
Yixuan Xue, Jin-Wu Jiang, Harold S. Park
Summary: Fullerene-based sandwiches with controllable physical properties offer new possibilities for advancing thermoelectricity. This study investigates the structural transformations of the sandwich structure and reveals the critical area ratios at which the fullerene pattern changes from circular to rectangular and the graphene layers become separated. These findings provide important insights into the mechanisms driving fullerene-based sandwich transformation, facilitating the design of future electronic and energy storage applications.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2023)
Article
Geochemistry & Geophysics
H. Luo, B. B. Karki, D. B. Ghosh, H. Bao
Summary: This study uses molecular dynamics simulations to show that the isotopic diffusion fractionation coefficient of helium in albite melt decreases with temperature, while the coefficient in model basalt melt is smaller than that in albite melt. It suggests using new isotopic ratios to interpret helium concentration and isotope composition in natural magmas.
GEOCHEMICAL PERSPECTIVES LETTERS
(2021)
Article
Chemistry, Physical
Patrick K. Schelling
Summary: The Soret effect describes the concentration gradients in fluid mixtures under a temperature gradient. By using molecular-dynamics simulation, it has been shown that spatially sinusoidal heat pulses can generate temperature and pressure gradients. Compressional waves are the dominant effect over short timescales, dissipating as the system approaches mechanical equilibrium. Concentration gradients quickly develop during the propagation of compressional waves. Over longer timescales, heat conduction returns the system to thermal equilibrium, restoring a more uniform particle density.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Review
Biochemistry & Molecular Biology
Dmitry Tolmachev, Natalia Lukasheva, Ruslan Ramazanov, Victor Nazarychev, Natalia Borzdun, Igor Volgin, Maria Andreeva, Artyom Glova, Sofia Melnikova, Alexey Dobrovskiy, Steven A. Silber, Sergey Larin, Rafael Maglia de Souza, Mauro Carlos Costa Ribeiro, Sergey Lyulin, Mikko Karttunen
Summary: This review focuses on the computational research of deep eutectic solvents (DESs), describing the technical features of DES simulations and discussing various DES applications. The aim is to demonstrate the current frontiers of computational research of DESs and discuss future perspectives.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Polymer Science
Victor M. Nazarychev, Gleb V. Vaganov, Sergey Larin, Andrey L. Didenko, Vladimir Yu Elokhovskiy, Valentin M. Svetlichnyi, Vladimir E. Yudin, Sergey Lyulin
Summary: It has been found that the mechanical properties of thermoplastic semi-crystalline polyimides can be enhanced by a strong structural ordering near single-walled carbon nanotubes (SWCNTs). In this study, a comparative analysis of computer simulations and experimental measurements was performed to investigate the rheological properties of nanocomposites based on thermoplastic semi-crystalline polyimide R-BAPB synthesized with SWCNTs. The results show that the viscosity of SWCNT-filled R-BAPB increases in the melt state due to the structural ordering near SWCNTs. Additionally, the orientation of polyimide chains near the SWCNT surface leads to anisotropic rheological properties and improved mechanical characteristics of the nanocomposites in the glassy state.
Article
Chemistry, Physical
S. V. Larin, V. V. Makarova, S. N. Gorbacheva, M. R. Yakubov, S. V. Antonov, N. I. Borzdun, A. D. Glova, V. M. Nazarychev, A. A. Gurtovenko, S. V. Lyulin
Summary: In this study, polymer additive P3HT was added to paraffin-carbon nanoparticle blends to improve their sedimentation stability, reduce the size of nanoparticle aggregates, and increase the viscosity of the blends. The presence of P3HT had almost no effect on the thermophysical properties of the blends, preserving their critical properties for heat storage applications.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Natalia Borzdun, Artyom Glova, Sergey Larin, Sergey Lyulin
Summary: This study investigates the relationships between the chemical structure of asphaltenes and the morphology of P3HT/asphaltene blends for BHJ solar cells. Molecular dynamics simulations show that carboxyl-containing asphaltenes can lead to the formation of heterophase morphology and highly ordered stacks, with additional stabilizing factors like hydrogen bonding required in blends with conjugated polymers. Aliphatic side groups in asphaltenes can improve miscibility and prevent heterophase morphology. Maintaining a certain ratio of carboxyl-containing asphaltenes to P3HT is crucial for polymer chain folding and blend morphology.
Article
Biochemistry & Molecular Biology
Alexey Y. Dobrovskiy, Victor M. Nazarychev, Igor V. Volgin, Sergey Lyulin
Summary: The effect of polymer chain ordering on the transport properties of the polymer membrane was examined for the semi-crystalline heterocyclic polyetherimide (PEI) BPDA-P3 based on all-atom Molecular Dynamics (MD) simulations. It was found that the solubility of gases decreased due to the redistribution of free volume elements occurring during the structural ordering of the polymer chains in glassy state. Gas diffusion anisotropy was observed in the ordered state, but the average diffusion coefficients did not differ between the amorphous and ordered states. Permeability in the system was primarily determined by gas solubility rather than gas diffusion.
Article
Biochemistry & Molecular Biology
Victor M. Nazarychev, Artyom D. Glova, Sergey V. Larin, Alexey V. Lyulin, Sergey V. Lyulin, Andrey A. Gurtovenko
Summary: An insight into the impact of cooling rate on phase transformations in molecular systems was gained through computational simulations on organic phase-change materials. It was found that a certain threshold in cooling rates exists, below which the simulations qualitatively reproduced experimental observations, and beyond which the simulations started to deviate considerably from experimental data.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Chemistry, Multidisciplinary
Igor V. Volgin, Pavel A. Batyr, Andrey V. Matseevich, Alexey Yu. Dobrovskiy, Maria V. Andreeva, Victor M. Nazarychev, Sergey V. Larin, Mikhail Ya. Goikhman, Yury V. Vizilter, Andrey A. Askadskii, Sergey V. Lyulin
Summary: This study addresses the problem of predicting the thermal properties of polymers using machine learning methods. A graph convolutional neural network (GCNN) is developed and trained using a transfer learning approach with synthetic and experimental data sets. The results show that pretraining the GCNN on the synthetic polymer data set provides better prediction accuracy compared to using other data sets. The study highlights the importance of using polymer data sets for developing deep neural networks for efficient prediction of polymer properties.
Article
Polymer Science
Sofia D. Melnikova, Sergey V. Larin
Summary: The effect of layer thickness and polymers compatibility on the structure and properties of coextruded multilayer polymer films was studied using molecular dynamics simulations. The results show that films with incompatible polymers have stable structures and low interfacial diffusion depth, even at nanoscale layer thickness. These films also exhibit anisotropic polymer atom mobility and two glass transition temperatures. In contrast, films with compatible polymers have a single glass transition point and gradually increasing interfacial diffusion depth. The findings suggest the importance of understanding the relationship between layer thickness and polymers compatibility in designing multilayer polymer films.
JOURNAL OF POLYMER SCIENCE
(2023)
Article
Chemistry, Physical
Andrey A. A. Gurtovenko, Victor M. M. Nazarychev, Artem D. D. Glova, Sergey V. V. Larin, Sergey V. V. Lyulin
Summary: In this study, a coarse-grained Martini model was developed to simulate the aggregation behavior of asphaltenes. It was found that native asphaltenes form small clusters that are uniformly distributed in the system, while modified asphaltenes form larger aggregates. Additionally, the mobility of native asphaltenes is slower and the size of aggregates increases with system size.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Polymer Science
A. A. Askadskii, A. V. Matseevich, I. V. Volgin, S. V. Lyulin
Summary: The approach to predict the permeability of polymer membranes based on polyimides and polyamidoimides towards helium is described. The activation energy of helium penetration is represented by a relationship involving the van der Waals volume of the repeat unit and a set of atomic parameters characterizing the contribution of each atom and intermolecular interaction types. Factors such as the imide cycles, connection type, and polar groups have been taken into account. The obtained parameters show a strong correlation coefficient of 0.965 with the experimental data, demonstrating the possibility to search for polyimide and polyamidoimide structures with the desired permeability without the need for laborious and expensive experiments.
POLYMER SCIENCE SERIES A
(2023)
Article
Polymer Science
Victor M. Nazarychev, Sergey V. Lyulin
Summary: In recent decades, there has been a growing interest in improving the thermal conductivity of polymers for the development of new thermal interface materials (TIM) for electronic and electrical devices. In this study, the effects of uniaxial deformation on the thermal conductivity of thermoplastic polyimides were examined using atomistic computer simulations. The results showed that the thermal conductivity coefficient is anisotropic in different directions and significantly increases in the direction parallel to the deformation.
Article
Chemistry, Physical
Artem D. Glova, Victor M. Nazarychev, Sergey V. Larin, Andrey A. Gurtovenko, Sergey V. Lyulin
Summary: Atomistic computer simulations suggest that asphaltenes with enlarged aromatic cores can improve the performance of heat storage devices based on organic phase change materials. Increasing the size of the asphaltene cores promotes the formation of extended structures in paraffin and enhances the thermal conductivity of liquid paraffin.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)