Illustrating the Molecular Origin of Mechanical Stress in Ductile Deformation of Polymer Glasses

Li, Xiaoxiao; Liu, Jianning; Liu, Zhuonan; Tsige, Mesfin; Wang, Shi‐Qing

doi:10.1103/physrevlett.120.077801

Cited by 21 publications

(26 citation statements)

References 35 publications

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“…Tightly entangled systems' D min 2 is maximally spatially correlated at γ ≃ γ yield but maximally topologically correlated at γ ≃ γ frac . This distinction indirectly supports the notion that polymer glasses yield when their "primary network" 26,27,74 of short-ranged van der Waals interactions fails but that in ductile polymers the entanglement network stabilizes further relatively homogeneous deformation until ultimate failure via chain pullout and scission. 1,2 4.…”

Section: Macromoleculessupporting

confidence: 58%

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms

Nguyen

Hoy

2018

Macromolecules

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Using molecular dynamics simulations, we study how chain stiffness affects how glassy polymers deform under applied shear. Loosely entangled systems composed of flexible chains exhibit strong shear banding and subsequent strain softening whereas tightly entangled systems composed of semiflexible chains exhibit neither of these. For all systems, inflection points in stress–strain curves correspond to the onset of chain scission, but nonlinear strain hardening continues up to much larger strains. Tightly entangled systems build up considerable elastic energy before fracturing via chain scission. This causes their plastic flow to be far more heterogeneous, and they ultimately fail along significantly sharper fracture planes than their loosely entangled counterparts, which fail via chain pullout. We quantify these differences using modern plasticity metrics and relate them to chain-stiffness-dependent differences in segmental packing efficiency and interchain interpenetration. It appears that the additional stress transmission mechanisms provided by the greater covalent bond tensions present in tightly entangled systems act to delocalize strain and promote more homogeneous deformation than is found in loosely entangled systems, but only until chain scission begins.

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Section: Macromoleculessupporting

confidence: 58%

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms

Nguyen

Hoy

2018

Macromolecules

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“…The glass transition temperature ( T g ) for a conjugated polymer is another important parameter for gauging the degree of ductility . Typically, a lower backbone T g corresponds to a higher tendency for plastic deformation upon stretching.…”

Section: Resultsmentioning

confidence: 99%

An Intrinsically Stretchable High‐Performance Polymer Semiconductor with Low Crystallinity

Zheng

Wang

Kang

et al. 2019

Adv Funct Materials

141

218

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For wearable and implantable electronics applications, developing intrinsically stretchable polymer semiconductor is advantageous, especially in the manufacturing of large-area and high-density devices. A major challenge is to simultaneously achieve good electrical and mechanical properties for these semiconductor devices. While crystalline domains are generally needed to achieve high charge carrier mobilities, amorphous domains are necessary to impart stretchability. Recent progresses in the design of high-performance donor-acceptor polymers which exhibited low degrees of energetic disorder, while having high fraction of amorphous morphology, appears promising for polymer semiconductors. Here, a low crystalline, i.e. near-amorphous, indacenodithiophene-co-benzothiadiazole (IDTBT) polymer and a semi-crystalline thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTT) are compared, for mechanical properties and electrical performance under applied strains. It is observed that the low crystalline IDTBT is able to achieve both high modulus and high fracture strain, and to preserve electrical functionality under high strain. Next, fully stretchable transistors are fabricated using the IDTBT polymer, and observed mobility ~0.6 cm 2 V-1 s-1 at 100% strain along stretching direction. In addition, the morphological evolution of the stretched IDTBT films is investigated by polarized UV-Vis and GIXD to elucidate the molecular origins of high ductility. In summary, the nearamorphous IDTBT polymer signifies a promising direction regarding molecular design principles toward intrinsically stretchable high-performance polymer semiconductor.

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“…To test the performance of CG models in nonequilibrium simulations of polymers, we simulate the mechanics of polymers in the glassy states using both CG model and all-atom (AA) and united-atom (UA) models. Glassy polymers are far from equilibrium, − and their mechanical response as a process out of equilibrium is critical to the application as low-cost and lightweight materials with sufficient strength. − Glassy polymer mechanics has been widely studied in experiments, − theory, − and simulations. ,− Specifically, the mechanics of glassy polystyrene (PS) is studied here. PS is a good model polymer due to its low glass-transition temperature and small polydispersity.…”

Section: Introductionmentioning

confidence: 99%

Effects of Coarse-Graining on Molecular Simulations of Mechanical Properties of Glassy Polymers

Wang

Robbins

2021

Macromolecules

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We simulate the mechanical response of polystyrene glasses using the models with different levels of coarse-graining but the same structural correlations at thermal equilibrium. The stress level during the strain hardening at the same temperature and deformation rate decreases as the degree of coarse-graining increases, reflecting that the configurational average of fine-grained structure leads to a smoother coarse-grained potential with lower energy barriers between local configurations. However, the stress–strain curves with different degrees of coarse-graining can be collapsed with a simple rescaling factor. The decomposition of the total stress σ into the energetic component σ U and the dissipative component σ Q shows that the same rescaling factor can be used to collapse σ U and σ Q . The range of strain for the collapses is before the significant increase in σ U , which is affected by the interaction details of a model. In the same strain range, the conformational changes in local chain segments are almost the same for different models. The strain rate dependencies of the stress levels in different models are universal as well. We demonstrate the feasibility of a scale-bridging simulation method that is based on the universal features of strain hardening in different models of polystyrene. The method uses the coarse-grained model to accelerate the simulation of mechanical response, while the atomistic model is used to capture the accurate stress level.

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Illustrating the Molecular Origin of Mechanical Stress in Ductile Deformation of Polymer Glasses

Cited by 21 publications

References 35 publications

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms

An Intrinsically Stretchable High‐Performance Polymer Semiconductor with Low Crystallinity

Effects of Coarse-Graining on Molecular Simulations of Mechanical Properties of Glassy Polymers

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Illustrating the Molecular Origin of Mechanical Stress in Ductile Deformation of Polymer Glasses

Cited by 21 publications

References 35 publications

Effect of the Ratio lK/p on Glassy-Polymeric Shear Deformation Mechanisms

Effect of the Ratio lK/p on Glassy-Polymeric Shear Deformation Mechanisms

An Intrinsically Stretchable High‐Performance Polymer Semiconductor with Low Crystallinity

Effects of Coarse-Graining on Molecular Simulations of Mechanical Properties of Glassy Polymers

Contact Info

Product

Resources

About

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms

Effect of the Ratio l_K/p on Glassy-Polymeric Shear Deformation Mechanisms