Faculty Profiles - MASUBUCHI Yuichi

Papers - MASUBUCHI Yuichi

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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

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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

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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

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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

Brownian simulations for tetra-gel-type phantom networks composed of prepolymers with bidisperse arm length Invited Reviewed International journal

Yuichi Masubuchi, Ryohei Yamazaki, Yuya Doi, Takashi Uneyama, Naoyuki Sakumichi, Takamasa Sakai

Soft Matter Vol. 18 ( 25 ) page： 4715 - 4724 2022.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)

Using Brownian dynamics simulations, we studied the mechanical properties of tetra-gel-type networks with varying arm length contrast of prepolymers to modulate the number of double linkages.

DOI： 10.1039/d2sm00488g

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Effects of Slip-Spring Parameters and Rouse Bead Density on Polymer Dynamics in Multichain Slip-Spring Simulations Invited Reviewed International journal

Yuichi Masubuchi, Yuya Doi, Takashi Uneyama

The Journal of Physical Chemistry B Vol. 126 ( 15 ) page： 2930 - 2941 2022.4

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

Masubuchi Y., Yang L., Uneyama T., Doi Y.

Polymers Vol. 14 ( 4 ) page： 741-1 - 741-15 2022.2

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

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.

DOI： 10.3390/polym14040741

Scopus

Nonlinear Shear and Elongational Rheology of Poly(propylene carbonate) Reviewed International journal

Yang Lixin, Uneyama Takashi, Masubuchi Yuichi, Doi Yuya

Nihon Reoroji Gakkaishi Vol. 50 ( 1 ) page： 127 - 135 2022

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

Nonlinear shear and elongational rheology of entangled poly(propylene carbonate) (PPC) melts having different molecular weights with relatively narrow molecular weight distribution are examined. In shear measurements, the PPCs exhibit a typical shear thinning behavior with stress overshoot at high shear rates. In the shear rate dependence of the steady-state viscosity, the PPCs do not violate the empirical Cox-Merz rule, which is known to be valid for many other entangled polymer melts. In uniaxial elongational measurements, the viscosity growth functions of the PPCs show a weak deviation from the linear viscoelastic (LVE) envelope to the higher side at the high Weissenberg number Wid (=ετd, where ε is the elongation rate and τd is the characteristic disengagement time). The steady-state viscosity of the PPCs shows an elongational thinning as a function of ε −0.5 within an error. These results are similar to some other polymer melts such as polystyrene (PS). In addition, the normalized elongational viscosity growth functions of PPC and PS with a similar entanglement number Z, are compared. The PPC exhibits a similar viscosity growth curve to the PS at the same Wid. This result suggests that the degree of the monomeric friction reduction originated from the stretch/orientation of PPC under fast elongational flow might occur at the same level as PS.

DOI： 10.1678/rheology.50.127

Scopus

Rheological properties of linear and short-chain branched polyethylene with nearly monodispersed molecular weight distribution Reviewed International journal

Takumitsu Kida, Yuya Doi, Ryo Tanaka, Takashi Uneyama, Takeshi Shiono, Yuichi Masubuchi

Rheologica Acta Vol. 60 ( 9 ) page： 511 - 519 2021.7

Wall slip in primitive chain network simulations of shear startup of entangled polymers and its effect on the shear stress undershoot Reviewed International coauthorship International journal

Yuichi Masubuchi, Dimitris Vlassopoulos, Giovanni Ianniruberto, Giuseppe Marrucci

Journal of Rheology Vol. 65 ( 2 ) page： 213 - 223 2021.3

Quantitative bridging between full-atomistic and bead-spring models for polybutadiene and poly(butadiene-styrene) copolymers Reviewed International journal

Akinori Baba, Yuichi Masubuchi

Journal of Chemical Physics Vol. 154 ( 4 ) page： 044901-1 - 044901-14 2021.1

DNA-Chitosan Hydrogels: Formation, Properties, and Functionalization with Catalytic Nanoparticles Reviewed International coauthorship International journal

Kohki Morikawa, Yuichi Masubuchi, Yury Shchipunov, Anatoly Zinchenko

ACS Applied Bio Materials Vol. 4 page： 1823 - 1832 2021

Plateau Moduli of Several Single-Chain Slip-Link and Slip-Spring Models Reviewed International journal

Takashi Uneyama, Yuichi Masubuchi

Macromolecules Vol. 54 ( 3 ) page： 1338 - 1353 2021

Radial Distribution Functions of Entanglements in Primitive Chain Network Simulations Reviewed International journal

Masubuchi Yuichi, Kida Takumitsu, Doi Yuya, Uneyama Takashi

Nihon Reoroji Gakkaishi Vol. 49 ( 5 ) page： 337 - 345 2021

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

Although the entanglement network among polymers has been widely investigated, the spatial distribution of entanglement nodes has been rarely discussed. In this study, we obtained the radial distribution functions (RDFs) for the entanglement nodes from the snapshots of multi-chain slip-link simulations. The model employed in this study is the primitive chain network (PCN) model, which has been validated to reproduce the entangled polymer dynamics semi-quantitatively. The statistics of captured entanglement networks were compared to those reported for the primitive path network extracted by the CReTA procedure from the full-atomistic molecular model of a polyethylene melt. In the range of distance longer than the average strand length, the network structure from PCN does not show any structural correlation, and the intra-chain correlation is close to that for Gaussian chains with non-interacting slip-links. These features are consistent with the CReTA network and the conventional assumptions made for single-chain models. Meanwhile, in the short-range, the structural correlation in PCN is much weaker than that in CReTA. This discrepancy is because the short-range structure in PCN is realized as a result of imposed fluctuations, whereas it is determined by the minimization of the primitive path in CReTA.

DOI： 10.1678/rheology.49.337

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Papers - MASUBUCHI Yuichi