Manipulating the Void Nucleation and Propagation in Silica Nanoparticle/Polyisoprene Nanocomposites via Grafted Chains: A Multiscale Simulation

Ma, Ruibin; Zhang, Wenfeng; Wang, Yimin; Li, Haoxiang; Zhao, Xiuying; Li, Xiaolin; Zhang, Liqun; Gao, Yangyang

doi:10.1021/acs.macromol.3c01387

Cited by 3 publications

(1 citation statement)

References 67 publications

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“…The systems are considered to reach the equilibration state where the density, temperature, energy, and chain size are stable. Finally, the triaxial tensile deformation is chosen to induce the void and fracture of systems, which is a very important method to study the fracture toughness. − It is noted that the CG potential functions of PU are transferable for different densities and contents of HS because of the same chemical property. During the deformation process, the box length along the tensile direction is elongated at a constant rate of 1 × 10 10 s –1 .…”

Section: Model and Simulation Detailsmentioning

confidence: 99%

Insight into the Fracture Properties and Molecular Mechanism of Polyurethane

Ma,

Wang,

Huang

et al. 2024

Macromolecules

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Polyurethane (PU) has an excellent mechanical property due to its unique microphase separated structure, but the molecular mechanism is still unclear. In this work, a multiscale model and the corresponding potential functions of PU are first developed via an inverse Boltzmann iterative method. Following it, the fracture toughness of PU is explored via a triaxial deformation, which exhibits a rise with the increase in the content of hard segments (HS). By analyzing the stress decomposition, morphology, and conformation of two phases, the HS phase can act as physical cross-links due to the strong phase strength, which mainly improves the tensile stress at the low strain. The soft segment (SS) phase contributes to the stress enhancement at high strain due to the large elongation. This microstructural evolution can be visualized by characterizing the von Mises strain and the local bead stress, which denote the microscopic strain and stress, respectively. Finally, the volume fraction, number, and surface area of voids are quantified to record their nucleation positions and growth process, which is based on the Voronoi volume of beads. Most of the voids are nucleated in the SS phase, while others are at the phase interface, which is consistent with the distribution snapshots of local elastic modulus. Moreover, the strong HS phase can inhibit the premature nucleation, growth, and mergence of voids, which enhances the fracture toughness. However, it is contrary with increasing the temperature. In summary, our work provides a novel and insightful understanding of the molecular mechanism of fracture toughness of PU.

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Section: Model and Simulation Detailsmentioning

confidence: 99%

Insight into the Fracture Properties and Molecular Mechanism of Polyurethane

Ma,

Wang,

Huang

et al. 2024

Macromolecules

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Influence of Number and Strength of Hydrogen Bonds on Fracture Property and Microscopic Mechanisms of Associative Hydrogen-Bonded Polymers via Molecular Dynamics Simulation

Wang,

Ma,

Wang

et al. 2024

Langmuir

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A coarse-grained model combining the acceptor− hydrogen−donor 3-body potential is first developed in this work to explore the fracture property and microscopic mechanisms of associative hydrogen-bonded polymers (AHBPs). Next, a triaxial deformation mode is performed to reveal that the fracture toughness of AHBPs initially improves and then is reduced as the number of active groups increases. By characterizing the stress decomposition, the strong hydrogen bond (HB) network improves the maximum stress but reduces the elongation. The destructive process of the HB network is described by quantifying the broken number and reduced energy of HBs. Interestingly, the strength of a single HB first decreases and then rises with strain. The initial decrease is mainly caused by the disruption of strong/moderate HBs, while the following rise is due to the further breakage of weak HBs and partial recovery of strong/moderate HBs. Meanwhile, the formed clusters of HBs due to the self-attraction act as the physical cross-links, whose evolution process is recorded by analyzing their number and size. Following it, the orientation degree and asphericity factor are calculated with strain to reflect the change in chain configuration, which is influenced by the HB network. Subsequently, the nucleation and growth process of voids is quantified. More than 90% of voids are nucleated in the polymer region, while others are in the HB region, which can be proved by the local elastic modulus and snapshots. The growth and coalescence rate of the voids can be suppressed by the strong HB network. Finally, the fracture toughness of AHBPs exhibits a continuous increase with improving strength of HBs due to the strong HB network. In summary, our work presents a clear and novel comprehension of the fracture property of AHBPs at the molecular scale.

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Molecular Insights into the Topological Transition, Fracture, and Self-Healing Behavior of Vitrimer Composites with Exchangeable Interfaces

Ma,

Wu,

et al. 2024

Macromolecules

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It is a significant challenge to prepare polymer materials with both high mechanical properties and recyclability. By introducing dynamic covalent bonds (DCBs), the nanorod-filled vitrimer composite (NVC) with exchangeable interfaces is a promising route to solve it, but the molecular mechanism is unclear. In this work, a coarse-grained model coupled with bond exchange reactions is developed to investigate the topological transition, fracture, and self-healing behavior of NVCs with exchangeable interfaces. First, the topology freezing transition temperature rises with the decreasing density (ρDCB) of the DCB or the increasing bond swap energy barrier (ΔE sw), while the glass transition temperature is nearly unchanged. Based on a continuum mechanics model, the fracture energy of the NVC is then analyzed by adopting a triaxial deformation, which rises with the increasing ρDCB and ΔE sw due to the enhanced network via the DCB. The stress decomposition, stretch ratio of network strands, von Mises strain, and local bead stress are characterized to understand the microstructural evolution, which is consistent with the fracture energy. Following it, the volume fraction and number of voids are recorded to analyze the nucleation positions, growth, and coalescence process of voids. The voids initially appear in the polymer matrix at the low strain, which owns a low local elastic modulus, while most of the voids are nucleated in the positions of the extended DCB at the large strain. The introduced DCB can inhibit the growth and coalescence rate of voids, which improves the fracture energy. Finally, the simulated self-healing efficiency is highest at the intermediate ρDCB, while it is reduced with the increasing ΔE sw. The relationship among the self-healing efficiency, healing temperature, and healing time follows the time–temperature superposition relationship. In summary, our work provides an in-depth theoretical analysis of the topological transition, fracture, and self-healing property of NVCs.

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Manipulating the Void Nucleation and Propagation in Silica Nanoparticle/Polyisoprene Nanocomposites via Grafted Chains: A Multiscale Simulation

Cited by 3 publications

References 67 publications

Insight into the Fracture Properties and Molecular Mechanism of Polyurethane

Insight into the Fracture Properties and Molecular Mechanism of Polyurethane

Influence of Number and Strength of Hydrogen Bonds on Fracture Property and Microscopic Mechanisms of Associative Hydrogen-Bonded Polymers via Molecular Dynamics Simulation

Molecular Insights into the Topological Transition, Fracture, and Self-Healing Behavior of Vitrimer Composites with Exchangeable Interfaces

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