Stress Undershoot of Entangled Polymers under Fast Startup Shear Flows in Primitive Chain Network Simulations

Masubuchi, Yuichi; Ianniruberto, Giovanni; Marrucci, G.

doi:10.1678/rheology.46.23

Cited by 23 publications

(19 citation statements)

References 22 publications

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“…They examined segmental orientation, tube stretch, and the ensemble average squared sine of the chain end-to-end orientation angle (representing the tumbling motion) and showed that all these variables exhibit undershoots, although not synchronized with shear stress. Masubuchi et al [43] concluded that their results supported the mechanism proposed by Costanzo et al [16]…”

Section: Resultssupporting

confidence: 61%

“…This may be due to the relatively low entanglement density of the C 400 H 802 molecules used in their NEMD simulations. Masubuchi et al [43] also investigated the origin of the stress undershoot at high shear rates using primitive chain network simulations. They examined segmental orientation, tube stretch, and the ensemble average squared sine of the chain end-to-end orientation angle (representing the tumbling motion) and showed that all these variables exhibit undershoots, although not synchronized with shear stress.…”

Section: Resultsmentioning

confidence: 99%

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Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics

2019

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The startup and steady shear flow properties of an entangled, monodisperse polyethylene liquid (C1000H2002) were investigated via virtual experimentation using nonequilibrium molecular dynamics. The simulations revealed a multifaceted dynamical response of the liquid to the imposed flow field in which entanglement loss leading to individual molecular rotation plays a dominant role in dictating the bulk rheological response at intermediate and high shear rates. Under steady shear conditions, four regimes of flow behavior were evident. In the linear viscoelastic regime ( γ ˙ < τ d − 1 ), orientation of the reptation tube network dictates the rheological response. Within the second regime ( τ d − 1 < γ ˙ < τ R − 1 ), the tube segments begin to stretch mildly and the molecular entanglement network begins to relax as flow strength increases; however, the dominant relaxation mechanism in this region remains the orientation of the tube segments. In the third regime ( τ R − 1 < γ ˙ < τ e − 1 ), molecular disentangling accelerates and tube stretching dominates the response. Additionally, the rotation of molecules become a significant source of the overall dynamic response. In the fourth regime ( γ ˙ > τ e − 1 ), the entanglement network deteriorates such that some molecules become almost completely unraveled, and molecular tumbling becomes the dominant relaxation mechanism. The comparison of transient shear viscosity, η + , with the dynamic responses of key variables of the tube model, including the tube segmental orientation, S , and tube stretch, λ , revealed that the stress overshoot and undershoot in steady shear flow of entangled liquids are essentially originated and dynamically controlled by the S x y component of the tube orientation tensor, rather than the tube stretch, over a wide range of flow strengths.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics

2019

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“…(G 0 is thermal energy per unit volume.) The parameters are insensitive to flow and deformation [15,35,38,57,[60][61][62][63][64].…”

Section: Model and Simulationsmentioning

confidence: 99%

Analysis of Elongational Viscosity of Entangled Poly (Propylene Carbonate) Melts by Primitive Chain Network Simulations

et al. 2022

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It has been established that the elongational rheology of polymers depends on their chemistry. However, the analysis of experimental data has been reported for only a few polymers. In this study, we analyzed the elongational viscosity of poly (propylene carbonate) (PPC) melts in terms of monomeric friction via primitive chain network simulations. By incorporating a small polydispersity of materials, the linear viscoelastic response was semi-quantitatively reproduced. Owing to this agreement, we determined units of time and modulus to carry out elongational simulations. The simulation with constant monomeric friction overestimated elongational viscosity, whereas it nicely captured the experimental data if friction decreased with increasing segment orientation. To see the effect of chemistry, we also conducted the simulation for a polystyrene (PS) melt, which has a similar entanglement number per chain and a polydispersity index. The results imply that PPC and PS behave similarly in terms of the reduction of friction under fast deformations.

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“…Masubuchi et al [33] reproduce the probe rheology data reported by Matsumiya et al [30] using primitive chain network (PCN) model, which describes the dynamics of the network formed by the primitive chains and is used extensively in literature [34][35][36][37][38]. Their results agree with the experiment well.…”

Section: Introductionmentioning

confidence: 62%

Slip-spring simulations of different constraint release environments for linear polymer chains

Lin

Tan

2020

R. Soc. open sci.

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The constraint release (CR) mechanism has important effects on polymer relaxation and the chains will show different relaxation behaviour in conditions of monodisperse, bidisperse and other topological environments. By comparing relaxation data of linear polyisoprene (PI) chains dissolved in very long matrix and monodisperse melts, Matsumiya et al. showed that CR mechanism accelerates both dielectric and viscoelastic relaxation (Matsumiya et al. 2013 Macromolecules 46 , 6067. ( doi:10.1021/ma400606n )). In this work, the experimental data reported by Matsumiya et al. are reproduced using the single slip-spring (SSp) model and the CR accelerating effects on both dielectric and viscoelastic relaxation are validated by simulations. This effect on viscoelastic relaxation is more pronounced. The coincidence for end-to-end relaxation and the viscoelastic relaxation has also been checked using probe version SSp model. A variant of SSp with each entanglement assigning a characteristic lifetime is also proposed to simulate various CR environment flexibly. Using this lifetime version SSp model, the correct relaxation function can be obtained with equal numbers of entanglement destructions by CR and reptation/contour length fluctuation (CLF) for monodisperse melts. Good agreement with published experiment data is also obtained for bidisperse melts, which validates the ability to correctly describe the CR environment of the lifetime version model.

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Stress Undershoot of Entangled Polymers under Fast Startup Shear Flows in Primitive Chain Network Simulations

Cited by 23 publications

References 22 publications

Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics

Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics

Analysis of Elongational Viscosity of Entangled Poly (Propylene Carbonate) Melts by Primitive Chain Network Simulations

Slip-spring simulations of different constraint release environments for linear polymer chains

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