Faculty Profiles - MASUBUCHI Yuichi

Papers - MASUBUCHI Yuichi

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Phantom Chain Simulations for Fracture of End-linking Networks Reviewed International journal

Yuichi Masubuchi

Polymer Vol. 297 page： 126880-1 - 126880-8 2024.3

Phantom chain simulations for the effect of stoichiometry on the fracture of star-polymer networks Reviewed

Yuichi Masubuchi

Nihon Reoroji Gakkaishi Vol. 52 ( 1 ) page： 21 - 26 2024.2

Phantom chain simulations for fracture of polymer networks created from star polymer mixtures of different functionalities Reviewed International journal

Masubuchi Y.

Polymer Journal Vol. 56 page： 163 - 171 2023.12

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Journal

Fujiyabu et al. [1] experimentally reported that mixing of 3-arm star prepolymers into 4-arm analogs improves the toughness of the resultant polymer networks compared to that of the base network composed of only 4-arm star polymers. The present study investigated the mechanism of this phenomenon based on phantom chain simulations for polymer networks consisting of mixtures of star branch prepolymers with equal arm length and different arm numbers, (f1,f2)=(3, 4) , (3, 6) and (3, 8) , for various f1= 3 prepolymer fractions φ3 . These networks were created via end-linking reactions between prepolymers traced by a Brownian dynamics scheme, and the network structure was stored at different conversion ratios φc , ranging from 0.6 to 0.9. The cycle rank of the gelated networks ξ is entirely consistent with that given by mean-field theory, demonstrating that the examined network structure is statistically valid. The networks were stretched with energy minimization until the break, and fracture characteristics including strain at break εb , stress at break σb , work for fracture Wb , and the ratio of broken strands φbb , were obtained. Plots of εb , σb/ φbb , and Wb/ φbb versus ξ roughly follow the master curves reported for the base networks without mixing, implying that the change of fracture properties by the mixing of f1= 3 mainly corresponds to a decrease in ξ . The mixing slightly suppresses σb/ φbb and Wb/ φbb for large f2 cases compared to the base networks because of a biased breakage at the network strands without extenders, which are prepolymers with only two reacted arms. The analysis also revealed a new master curve for the ξ -dependence of the molecular weight of broken strands.

DOI： 10.1038/s41428-023-00862-w

Scopus

Modeling for Heterogeneous Oxidative Aging of Polymers Using Coarse-Grained Molecular Dynamics Reviewed International journal

Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi

Macromolecules Vol. 56 ( 21 ) page： 8474 - 8483 2023.11

Effects of attractive inter-particle interaction on cross-transport coefficient between mass and heat in binary fluids Reviewed International journal

Tatsuma Oishi, Yuya Doi, Yuichi Masubuchi, Takashi Uneyama

Molecular Simulation 2023.10

A Multi-Chain Slip-Spring Model without the Slip-Spring Degeneracy Reviewed International journal

Yuichi Masubuchi, Yuya Doi, Takato Ishida, Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 51 ( 4 ) page： 211 - 217 2023.10

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：The Society of Rheology, Japan

In the multi-chain slip-spring, the dynamics of Rouse chains connected by virtual springs called slip-springs that hop along the chain are considered. Although this approach has been proven to reproduce entangled polymer dynamics efficiently, the settings of the artificially introduced slip-springs should be carefully examined. In this study, we discussed the effect of the slip-spring degeneracy by limiting the number of anchored slip-springs on each Rouse bead to zero and one. According to the altered slip-spring statistics, we derived the compensation potential to eliminate the artifact of slip-springs on the chain statistics. With this potential, we performed numerical simulations. The results demonstrated that although we reasonably retain the Gaussian chain statistics, the dynamics deviate from the established entangled polymer dynamics because of the significant slow-down in the chain motion induced by the correlation between different slip-springs. The observed deceleration can be explained by the fact that the movement of slip-springs can be cast into an asymmetric exclusion process.

DOI： 10.1678/rheology.51.211

Extension of moving particle simulation by introducing rotational degrees of freedom for dilute fiber suspensions Reviewed International journal

Keigo Enomoto, Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi

International Journal for Numerical Methods in Fluids Vol. 96 page： 125 - 137 2023.9

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley

Abstract

We develop a novel Moving Particle Simulation (MPS) method to reproduce the motion of fibers floating in sheared liquids accurately. In conventional MPS schemes, if a fiber suspended in a liquid is represented by a one‐dimensional array of MPS particles, it is entirely aligned to the flow direction due to the lack of shear stress difference between fiber–liquid interfaces. To address this problem, we employ the micropolar fluid model to introduce rotational degrees of freedom into the MPS particles. The translational motion of liquid and solid particles and the rotation of solid particles are calculated with the explicit MPS algorithm. The fiber is modeled as an array of micropolar fluid particles bonded with stretching, bending and torsional potentials. The motion of a single rigid fiber is simulated in a three‐dimensional shear flow generated between two moving solid walls. We show that the proposed method is capable of reproducing the fiber motion predicted by Jeffery's theory which is different from the conventional MPS simulations.

DOI： 10.1002/fld.5235

Scopus

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Phantom-Chain Simulations for the Effect of Node Functionality on the Fracture of Star-Polymer Networks Reviewed International journal

Yuichi Masubuchi, Yuya Doi, Takato Ishida, Naoyuki Sakumichi, Takamasa Sakai, Koichi Mayumi, Kotaro Satoh, Takashi Uneyama

Macromolecules Vol. 56 ( 23 ) page： 9359 - 9367 2023.9

Preparation and characterization of two-dimensional sheet-shaped poly(methyl methacrylate) synthesized via γ-ray polymerization in nanoclay template Invited Reviewed International journal

Yuya Doi, Mitsuo Hara, Takahiro Seki, Atsushi Takano, Takato Ishida, Takashi Uneyama, Yuichi Masubuchi

Polymer Journal Vol. 55 ( 9 ) page： 957 - 965 2023.5

Undershoots in shear startup of entangled linear polymer blends Invited Reviewed International coauthorship International journal

Parisi Daniele, Vereroudakis Emmanouil, Masubuchi Yuichi, Ianniruberto Giovanni, Marrucci Giuseppe, Vlassopoulos Dimitris

JOURNAL OF NON-NEWTONIAN FLUID MECHANICS Vol. 315 2023.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Non-Newtonian Fluid Mechanics

We revisit the transient response of entangled polymers in shear startup. Evidence from state-of-the-art experiments, modeling and simulations suggests the presence in fast flows of a weak (albeit unambiguous) undershoot, following the overshoot, i.e., while approaching the steady state. Recent sliplink simulations confirmed that the undershoot is not due to slip at the wall, and hence it is intrinsic to polymer rheology. Here, we further examine some features of the undershoot by blending two entangled homopolymers at different compositions. Since blending affects the distribution of relaxation times, it is here shown to also affect the undershoot, probably by broadening the tumbling-time distribution. Indeed, by appropriately modifying our tube-based model, that invokes tumbling to account for the undershoot, and (in parallel) by using simulations, we show how the undershoot depends on the blend composition. We map the experimental results into a diagram of terminal relaxation time versus composition, which identifies regimes where the undershoot is present. Blending is therefore proposed as a molecular mechanism to tailor the shear stress growth function signal, particularly the undershoot.

DOI： 10.1016/j.jnnfm.2023.105028

Web of Science

Scopus

Primitive chain network simulations of the nonlinear rheology of polystyrene melts: Friction reduction and fluctuation-dissipation theorem Invited Reviewed International coauthorship International journal

Masubuchi Yuichi, Ianniruberto Giovanni, Wagner Manfred, Marrucci Giuseppe

JOURNAL OF NON-NEWTONIAN FLUID MECHANICS Vol. 315 2023.5

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Non-Newtonian Fluid Mechanics

Description of the elongational rheology of concentrated polymers appears to require that in fast flows the friction coefficient decreases with respect to its equilibrium value. However, the proposed models typically maintain the validity of the fluctuation-dissipation theorem (FDT) out of equilibrium. On the other hand, FDT is routed in local equilibrium, the latter being clearly violated by the flow-induced monomer coalignment that induces friction change. A recent analysis by Watanabe et al. [Macromolecules, 54, 3700 (2021)] of unentangled polystyrene (PS) melts, based on a nonlinear extension of the Rouse model, indicates that FDT is indeed violated in fast flows. According to their analysis, the Brownian force intensity remains almost independent of the flow rate, even though the friction coefficient drastically decreases. A different violation of FDT is shown by previous nonequilibrium molecular dynamics simulations of PS oligomers [Ianniruberto et al., Macromolecules, 45, 8058 (2012)] where the diffusion coefficient grows more than the inverse friction coefficient. In this paper, Brownian simulations using a multi-chain sliplink model (the so-called primitive chain network model) are reported for two monodisperse entangled PS melts, for which nonlinear shear and elongational data were published. Two different friction reduction models are examined, and the effect of switching FDT on and off is tested. Results demonstrate that, irrespective of FDT, both friction models can reasonably well reproduce the behavior shown by the data. This result lends support to models that retain FDT since its violation appears not to significantly affect predictions of nonlinear rheology.

DOI： 10.1016/j.jnnfm.2023.105019

Web of Science

Scopus

Increase in rod diffusivity emerges even in Markovian nature Reviewed International coauthorship International journal

Fumiaki Nakai, Martin Kröger, Takato Ishida, Takashi Uneyama, Yuya Doi, Yuichi Masubuchi

Physical Review E Vol. 107 ( 4 ) 2023.4

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Rod-shaped particles embedded in certain matrices have been reported to exhibit an increase in their center of mass diffusivity upon increasing the matrix density. This increase has been considered to be caused by a kinetic constraint in analogy with tube models. We investigate a mobile rodlike particle in a sea of immobile point obstacles using a kinetic Monte Carlo scheme equipped with a Markovian process, that generates gaslike collision statistics, so that such kinetic constraints do essentially not exist. Even in such a system, provided the particle's aspect ratio exceeds a threshold value of about 24, the unusual increase in the rod diffusivity emerges. This result implies that the kinetic constraint is not a necessary condition for the increase in the diffusivity.

DOI： 10.1103/PhysRevE.107.044604

Web of Science

Scopus

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Phantom Chain Simulations for the Fracture of Energy-Minimized Tetra- and Tri-Branched Networks Reviewed International journal

Yuichi Masubuchi, Yuya Doi, Takato Ishida, Naoyuki Sakumichi, Takamasa Sakai, Koichi Mayumi, Takashi Uneyama

Macromolecules 2023.2

Tube Survival Fraction in Primitive Chain Network Simulations Reviewed International journal

Masubuchi Yuichi

Nihon Reoroji Gakkaishi Vol. 51 ( 1 ) page： 19 - 24 2023.2

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：The Society of Rheology, Japan

In the framework of the tube model, the survival fraction of dilated tube, φʹ(t), is essential since the relaxation of the entire system is described according to this quantity. However, a method to define it in multi-chain simulations has yet to be considered. In this study, primitive chain network simulations were performed, and a few structural quantities were discussed as possible candidates for use as φʹ(t). Before analysis, the simulation was evaluated against literature data for linear polyisoprene melts, and quantitative agreement was obtained for viscoelastic and dielectric relaxations. Afterward, the end-to-end relaxation function was compared to survival probability of the slip link φs(t) and the ratio of monomers between the most distant surviving slip link pair to the total number of monomers ns(t)/nt. The result implies that ns(t)/nt is comparable to φʹ(t). Comparison to atomistic molecular dynamics (MD) simulations for polyethylene showed similar results, implying that φʹ(t) can be obtained even in MD simulations if the surviving entanglement points can be specified.

DOI： 10.1678/rheology.51.19

CiNii Research

Fluctuating diffusivity emerges even in binary gas mixtures Reviewed International journal

Nakai F., Masubuchi Y., Doi Y., Ishida T., Uneyama T.

Physical Review E Vol. 107 ( 1 ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Review E

Diffusivity in some soft matter and biological systems changes with time, called the fluctuating diffusivity. In this work, we propose a novel origin for fluctuating diffusivity based on stochastic simulations of binary gas mixtures. In this system, the fraction of one component is significantly small, and the mass of the minor component molecule is different from that of the major component. The minor component exhibits fluctuating diffusivity when its mass is sufficiently smaller than that of the major component. We elucidate that this fluctuating diffusivity is caused by the time scale separation between the relaxation of the velocity direction and the speed of the minor component molecule.

DOI： 10.1103/PhysRevE.107.014605

Scopus

Elongational viscosity of poly(propylene carbonate) melts: tube-based modelling and primitive chain network simulations Reviewed International coauthorship International journal

Wagner Manfred H., Narimissa Esmaeil, Masubuchi Yuichi

RHEOLOGICA ACTA Vol. 62 ( 1 ) page： 1 - 14 2023.1

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Rheologica Acta

In fast elongational flows, linear polymer melts exhibit a monotonic decrease of the viscosity with increasing strain rate, even beyond the contraction rate of the polymer defined by the Rouse time. We consider two possible explanations of this phenomenon: (a) the reduction of monomeric friction and (b) the reduction of the tube diameter with increasing deformation leading to an Enhanced Relaxation of Stretch (ERS) on smaller length scales. (Masubuchi et al. (2022) reported Primitive Chain Network (PCN) simulations using an empirical friction reduction model depending on segmental orientation and could reproduce the elongational viscosity data of three poly(propylene carbonate) melts and a polystyrene melt. Here, we show that the mesoscopic tube-based ESR model (Wagner and Narimissa 2021) provides quantitative agreement with the same data set based exclusively on the linear-viscoelastic characterization and the Rouse time. From the ERS model, a parameter-free universal relation of monomeric friction reduction as a function of segmental stretch can be derived. PCN simulations using this friction reduction relation are shown to reproduce quantitatively the experimental data even without any fitting parameter. The comparison with results of the earlier PCN simulation results with friction depending on segmental orientation demonstrates that the two friction relations examined work equally well which implies that the physical mechanisms of friction reduction are still open for discussion.

DOI： 10.1007/s00397-022-01373-w

Web of Science

Scopus

CNT Gels Formed by a Triptycene Analogue Enabling Coexistence of CNT-gelator and Intergelator Interactions Reviewed International journal

Ushiroguchi R., Suizu R., Matsunaga Y., Omachi H., Doi Y., Masubuchi Y., Bandow S., Awaga K.

Chemistry Letters Vol. 51 ( 11 ) page： 1070 - 1073 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters

We report carbon nanotube (CNT) gels, formed by mechanically mixing CNTs, organic solvents, and a small molecule, Trip-Phz, that have a strong affinity for fullerene materials. There is a clear threshold value in the amount of Trip-Phz needed for the transition from soft to hard gels.

DOI： 10.1246/cl.220319

Scopus

Viscoelastic properties of comb-shaped ring polystyrenes Invited Reviewed International journal

Doi Y., Kitamura J., Uneyama T., Masubuchi Y., Takano A., Takahashi Y., Matsushita Y.

Polymer Journal Vol. 54 ( 11 ) page： 1267 - 1277 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Journal

In this study, we examined the viscoelastic properties of a series of comb-shaped ring (RC) polystyrene samples with different branch chain lengths, i.e., the molecular weights of the ring backbone Mbb (≃ 4Me where Me is the entanglement molecular weight) and branch chains Mbr (≃ Me, 2Me, and 4Me). Even for the RC sample with the shortest branch chains, a plateau region was observed for the dynamic modulus G*(ω) in the middle angular frequency ω region, suggesting that intermolecular branch chain entanglement occurred. In the ω region between the plateau and terminal regions, G*(ω) was observed with a weaker ω dependence than the terminal relaxation. This behavior was more pronounced for RC samples with shorter branch chains and for the corresponding linear comb (LC) samples than for the RC ones. The molecular weight dependence of the zero-shear viscosity η0 and the steady-state recoverable compliance Jeo of the RC and LC samples was evaluated, and the effects of different backbone molecular structures (i.e., ring or linear) on the terminal relaxation behavior was discussed. Moreover, the G*(ω) data were analyzed with two models: the comb-Rouse model, in which the structures of the RC/LC molecules are taken into account by graph theory, and the Milner-McLeish model for entangled star-shaped polymers. The former model qualitatively described the terminal relaxation behavior of G*(ω) at low ω but failed to reproduce the plateau in the middle ω range. Conversely, the latter model described the entanglement plateau in the middle ω range, but the difference in the terminal relaxation regime for the RC/LC samples seen in the data and the comb-Rouse model disappeared.

DOI： 10.1038/s41428-022-00686-0

Scopus

Stress Tensor of Single Rigid Dumbbell by Virtual Work Method Reviewed International journal

Uneyama Takashi, Oishi Tatsuma, Ishida Takato, Doi Yuya, Masubuchi Yuichi

Nihon Reoroji Gakkaishi Vol. 50 ( 4 ) page： 313 - 322 2022.9

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：The Society of Rheology, Japan

We derive the stress tensor of a rigid dumbbell by using the virtual work method. In the virtual work method, we virtually apply a small deformation to the system, and relate the change of the energy to the work done by the stress tensor. A rigid dumbbell consists of two particles connected by a rigid bond of which length is constant (the rigid constraint). The energy of the rigid dumbbell consists only on the kinetic energy. Also, only the deformations which do not violate the rigid constraint are allowed. Thus we need the dynamic equations which are consistent with the rigid constraint to apply the virtual deformation. We rewrite the dynamic equations for the underdamped SLLOD-type dynamic equations into the forms which are consistent with the rigid constraint. Then we apply the virtual deformation to a rigid dumbbell based on the obtained dynamic equations. We derive the stress tensor for the rigid dumbbell model from the change of the kinetic energy. Finally, we take the overdamped limit and derive the stress tensor and the dynamic equation for the overdamped rigid dumbbell. We show that the Green-Kubo type linear response formula can be reproduced by combining the stress tensor and the dynamic equation at the overdamped limit.

DOI： 10.1678/rheology.50.313

Primitive Chain Network Simulations for Shear Rheology of Poly(propylene carbonate) Melts Reviewed International journal

Masubuchi Yuichi, Yang Lixin, Uneyama Takashi, Doi Yuya

Nihon Reoroji Gakkaishi Vol. 50 ( 4 ) page： 305 - 312 2022.9

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：The Society of Rheology, Japan

Although chemistry dependence in the non-linear rheology of polymers has been rather established for uniaxial elongations, it has not been frequently discussed for fast shear. In this study, to see the effect of orientation-dependent monomeric friction on the shear rheology, we conducted primitive chain network simulations for a few poly(propylene carbonate) melts, for which we have determined the friction model from the uniaxial data recently [Yang et al., Nihon Reoroji Gakkaishi, 50, 127–135 (2022)]. The simulation qualitatively reproduced typical non-linear behaviors, such as shear thinning and stress overshoot, under fast shears. The agreement with experimental data became better when the friction was varied according to the segment orientation. In particular, the shear rate dependence of the peak position for the stress overshoot (i.e., the peak stress and the strain at the peak) was better reproduced. This result implies that chemistry-dependent friction may probably be discussed from the stress overshoot under high shear.

DOI： 10.1678/rheology.50.305

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Papers - MASUBUCHI Yuichi