Article
Polymer Science
Takahiro Murashima, Katsumi Hagita, Toshihiro Kawakatsu
Summary: Coarse-grained molecular dynamics simulations were used to analyze blends of multicyclic and linear polymers under biaxial elongational flow. The blends exhibited an overshoot behavior in the normal stress difference, with multicyclic/linear blends showing a steeper overshoot compared to monocyclic/linear blends. The origin of the overshoot was found to be a topological transition mechanism in the multicyclic chains, which resulted in a drastic change in the stress of the rings.
Article
Chemistry, Physical
Yuki Mizuno, Yuansheng Zhao, Hiroshi Akiba, Shinji Kohara, Koji Ohara, Matthew G. Tucker, Marshall T. McDonnell, Osamu Yamamuro
Summary: This study prepared simple molecular glasses by using a novel cryostat and investigated the orientational correlation between liquid CS2 and glassy CS2. The results showed that at room temperature, the nearest neighbor correlation tended to be parallel and T-shaped arrangements, while in the glassy state, the dominant arrangement was slipped-parallel arrangement.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Materials Science, Biomaterials
A. P. P. Fugolin, A. R. Costa, S. H. Lewis, M. Goulart, M. C. Erhardt, C. S. Pfeifer
Summary: The addition of thiourethane prepolymer into composite materials can reduce polymerization stress and improve fracture toughness. The study indicates that thiourethane networks undergo various reversible chemical reactions, enhancing stress relief capabilities.
JOURNAL OF MATERIALS CHEMISTRY B
(2021)
Article
Polymer Science
Yuya Doi, Atsushi Takano, Yoshiaki Takahashi, Yushu Matsushita
Summary: The study found that dumbbell polymers form a unique network structure with distinctive entanglement characteristics in the system. Dumbbell PS samples with longer central chains exhibit slower terminal relaxation and retain entanglement features in high-concentration DOP solutions.
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
Chemistry, Physical
Daniele Coslovich, Robert L. Jack, Joris Paret
Summary: This study uses unsupervised learning methods to characterize the disordered microscopic structure of supercooled liquids and glasses. Dimensionality reduction is performed on smooth structural descriptors, and the ability of the method to capture the essential structural features of glassy binary mixtures is assessed. The results indicate that some mixtures have well-defined locally favored structures and are reflected in bimodal distributions of structural variables identified through dimensionality reduction.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
Debankur Das, Pappu Acharya, Kabir Ramola
Summary: The study focuses on displacement fields in two-dimensional athermal networks in response to external pinning forces, using a Green's function formalism to derive exact results. It is found that in the continuum limit, displacement fields decay as 1/r away from force dipoles. Furthermore, correlations in displacement fields produced by the external pinning forces are investigated, revealing long-range correlations in athermal systems with a nontrivial dependence on system size.
Article
Multidisciplinary Sciences
Jan Smrek, Jonathan Garamella, Rae Robertson-Anderson, Davide Michieletto
Summary: The study reveals that larger supercoiling in dense supercoiled DNA increases the size of entangled plasmids and enhances DNA mobility. These findings suggest a way to tune DNA mobility via supercoiling, enabling topological control over the (micro)rheology of DNA-based complex fluids.
Article
Engineering, Chemical
Fan Liu, Jin Wang, He Zhang, Xiaohu Yao
Summary: This paper employed an elastic-plastic constitutive model to predict and analyze the stress relaxation of a glassy polymer. It was found that the model accurately predicted pre-yield stress relaxation but underestimated post-yield stress relaxation. To address this issue, the model was extended to incorporate an additional structural relaxation mechanism originating from the dissociation of weak linkages in the chain network. The extended model successfully explained both the yield/flow and stress relaxation behaviors throughout the deformation region, and the reasons behind it were analyzed. The knowledge revealed in this paper is instructive and may provide new insights into understanding the structural relaxation and mechanical behavior of glassy polymers.
POLYMER ENGINEERING AND SCIENCE
(2023)
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
Polymer Science
Wenduo Chen, Shaonan Wei
Summary: This study utilized Langevin Dynamics Simulations to investigate the compression and relaxation processes of confined ring polymers in a nanochannel. The findings revealed that ring polymers exhibit complex deformations under different levels of confinement, with weakly confined polymers compressed into condensed blobs and strongly confined polymers undergoing deformations from double helix to collapsed states. During relaxation, weakly confined rings return to their initial states, while strongly confined rings extend from compacted states to randomly folded states due to interpenetrated and self-entangled structures formed during compression.
Article
Polymer Science
Jerome Hem, Caroline Crauste-Thibierge, Thomas C. Merlette, Florence Clement, Didier R. Long, Sergio Ciliberto
Summary: The study investigates the molecular dynamics of relaxation processes during plastic flow of glassy polymers under different deformation protocols using dielectric spectroscopy. It identifies variations in relaxation time and distribution width under different protocols, as well as behavioral differences in strain hardening regime under different strain protocols.
Article
Polymer Science
Guangjian Xiang, Deshun Yin, Ruifan Meng, Chenxi Cao
Summary: This article introduces a novel constitutive model using fractional calculus to capture the stress relaxation behavior of glassy polymers. Based on experimental data, it is concluded that the linear order function of time is suitable for the model and shows high accuracy. The increasing order of the function is found to have a direct connection with the continuous softening of polymers during relaxation.
POLYMERS FOR ADVANCED TECHNOLOGIES
(2021)
Article
Engineering, Chemical
Andreas Schoenhals, Paulina Szymoniak, Mohamed A. Kolmangadi, Martin Boehning, Michaela Zamponi, Bernhard Frick, Markus Appel, Gerrit Guenther, Margarita Russina, Dmitry A. Alentiev, Maxim Bermeshev, Reiner Zorn
Summary: The study found that poly(tricyclononenes) with Si-substituted bulky side groups have high microporosity, making them potential candidates for active separation layers for gas separation membranes. The low temperature relaxation process involving methyl group rotation suggests that some methyl groups may be immobilized in their rotation due to steric hindrance.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Article
Chemistry, Physical
A. Mansuri, P. Muenzner, T. Feuerbach, A. W. P. Vermeer, W. Hoheisel, R. Boehmer, M. Thommes, C. Gainaru
Summary: This study investigates the molecular dynamics of imidacloprid using dielectric spectroscopy, oscillatory shear rheology, and calorimetry, revealing that the molecular dynamics in its glassy state strongly depends on its thermal history. The research shows that different methods predict different relaxation times, indicating the complexity of imidacloprid's behavior in technological applications.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Mechanics
Thomas C. O'Connor, Ting Ge, Gary S. Grest
Summary: This study extensively uses molecular simulations to investigate the equilibrium dynamics, entanglement topology, and nonlinear extensional rheology of symmetric ring-linear polymer blends. The topological analysis reveals a critical ring fraction where the composite entanglement network exhibits maximum constraints. The study also identifies an extensional stress overshoot phenomenon in uniaxial elongation flows, and explains its underlying mechanism.
JOURNAL OF RHEOLOGY
(2022)
Article
Chemistry, Physical
Oleg Davydovich, Justine E. Paul, John David Feist, Jia En Aw, Francisco Javier Balta Bonner, Jacob J. Lessard, Sameh Tawfick, Yan Xia, Nancy R. Sottos, Jeffrey S. Moore
Summary: Frontal ring-opening metathesis polymerization (FROMP) is a rapid, low-energy manufacturing reaction used for curing thermosetting materials. Incorporating cleavable units in the chain segments allows for the deconstruction of thermosets. 2,3-dihydrofuran (DHF), acting as both a potent Grubbs catalyst inhibitor and an acid cleavable unit, enables the production of high-performance deconstructable thermosets.
CHEMISTRY OF MATERIALS
(2022)
Article
Polymer Science
Supun S. Mohottalalage, Chathurika Kosgallana, Shalika Meedin, Thomas C. O'Connor, Gary S. Grest, Dvora Perahia
Summary: Ionizable polymers form dynamic networks controlled by ionic interactions and van der Waals forces. Molecular dynamics simulations of a model ionizable polymer provide insight into its nonlinear response. Increasing elongational flow rate leads to an initial elastic response, followed by strain hardening, stress overshoot, and eventually strain thinning. Flow-driven ionic assembly dynamics control the system's response.
Article
Chemistry, Physical
Baicheng Mei, Tsai-Wei Lin, Charles E. E. Sing, Kenneth S. S. Schweizer
Summary: We generalize a microscopic statistical mechanical theory to study the influence of crosslinking in polymer networks on the penetrant relaxation time and diffusivity. Our calculations are relevant to recent experimental studies of a nm-sized molecule diffusing in polymer networks. The results show that the penetrant relaxation time increases with the glass transition temperature, which is linearly related to the square root of the crosslink fraction. A model for the penetrant diffusion constant is proposed, combining activated relaxation and entropic mesh confinement. This behavior corresponds to a new network-based type of decoupling of diffusion and relaxation.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Baicheng Mei, Tsai-Wei Lin, Grant S. Sheridan, Christopher M. Evans, Charles E. Sing, Kenneth S. Schweizer
Summary: The transport of penetrants through dense cross-linked polymer networks is influenced by various factors such as cross-link density, size ratio, and temperature. This study used a combination of experiment, simulation, and theory to investigate these effects and found that the coupling between local penetrant hopping and polymer structural relaxation is crucial, while mesh confinement effects are less important. The findings provide insights into the behavior observed in experiment and simulation and may contribute to the development of improved polymer membrane designs.
ACS CENTRAL SCIENCE
(2023)
Article
Chemistry, Physical
Tsai-Wei Lin, Baicheng Mei, Kenneth S. Schweizer, Charles E. Sing
Summary: The role of cross-linked network polymers in governing the molecular motion of penetrants is investigated using molecular simulation. The results show that cross-links primarily affect molecular diffusion through the modification of the matrix glass transition, and penetrant transport is affected by dynamic heterogeneity at low temperatures. This research provides important insights for the design of materials for applications such as coatings and membranes.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Polymer Science
Oleg Davydovich, Andrew J. Greenlee, Harrison D. Root, Annika L. Jansen, Shantae C. Gallegos, Matthew J. Warner, Michael S. Kent, Jorge A. Cardenas, Leah N. Appelhans, Devin J. Roach, Brad H. Jones, Samuel C. Leguizamon
Summary: Frontal polymerization is a method to rapidly generate high-performance polymeric materials through the propagation of a thermally driven polymerization wave. Encapsulated catalysts can provide remarkable latency to frontal polymerization systems, addressing the issue of poor storage lives caused by highly reactive catalysts.
Article
Chemistry, Multidisciplinary
Sidath Wijesinghe, Christoph Junghans, Dvora Perahia, Gary S. Grest
Summary: Soft nanoparticles formed by conjugated polymers interact with a model membrane, and neutral nanoparticles spontaneously penetrate the membrane while carboxylated nanoparticles must be driven in without significant disruption to the membrane.
Article
Physics, Fluids & Plasmas
Joseph M. Monti, Ishan Srivastava, Leonardo E. Silbert, Jeremy B. Lechman, Gary S. Grest
Summary: This study calculates the static structure factors of large-scale, mechanically stable, jammed packings of frictionless spheres and disks with broad size dispersity. The analysis of the power-law behavior of the structure factors reveals that in three dimensions, the structural fractal dimension (df) is approximately 2.0 for -beta values between 2.5 and 3.8, allowing the collapse of structure factors onto a universal curve. In two dimensions, the fractal dimension (df) ranges from 1.0 to 1.34 for -beta values between 2.1 and 2.9. Additionally, the fractal behavior persists even after removing rattler particles, indicating that the long-wavelength structural properties of the packings are controlled by the large particle backbone conferring mechanical rigidity to the system.
Article
Chemistry, Physical
Baicheng Mei, Kenneth S. Schweizer
Summary: The article applies the microscopic self-consistent cooperative hopping theory to study the activated penetrant dynamics in polymer melts and crosslinked networks. It focuses on the role of highly variable non-spherical molecular shape and examines its impact on penetrant hopping over a wide range of temperatures. The study reveals that the shape of the penetrant has a significant influence on its activated relaxation, with larger penetrants showing a stronger shape-dependence. A variable aspect ratio is proposed to describe the effect of penetrant shape on the relaxation times.