Faculty Profiles - UNEYAMA Takashi

Papers - UNEYAMA Takashi

Division display >> ／ All the affair displays 1 - 103 of about 103

Coarse-grained molecular dynamics simulations for oxidative aging of polymers under various O₂ concentrations Reviewed International journal Open Access

Ishida T., Haremaki K., Koide Y., Uneyama T., Masubuchi Y.

Polymer Degradation and Stability Vol. 239 2025.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Degradation and Stability

Modeling of polymer oxidative aging has been actively studied since the 1990s. Insights from these studies suggest that the transport of oxygen and radicals significantly influences aging heterogeneity, alongside chemical reaction kinetics. A recent simulation study [Ishida et al., Macromolecules, 56(21), 8474-8483, 2023] demonstrated that mesoscale heterogeneity arises when the H-abstraction reaction occurs faster than the relaxation times of polymer chains. In this study, the simulations were extended by modeling the rate of oxygen addition to polymer radicals (k2) to reflect the effects of the O₂ concentration. In this work, polypropylene was chosen as a representative example of the target polymer. Three key aspects of oxidative aging behavior were found to be influenced by the O2 addition rate: (i) reaction kinetics, (ii) the degree of heterogeneity, and (iii) amount of crosslinking. Namely, reducing O2 concentration slows the conversion of polymer radicals into H-abstractable peroxyl radicals. This deceleration delays H-abstraction reactions, increases the number of polymer radicals, and promotes crosslinking reactions between two polymer radicals.

DOI： 10.1016/j.polymdegradstab.2025.111404

Open Access

Scopus

Nonmonotonic concentration dependence of the self-diffusion coefficient of surfactants in wormlike micellar solutions. Reviewed International journal

Koide Y, Ishida T, Uneyama T, Masubuchi Y

The Journal of chemical physics Vol. 162 ( 17 ) 2025.5

Radius of Gyration in Shear Gradient Direction Governs Steady Shear Viscosity of Rouse-Type Model Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 53 ( 1 ) page： 11 - 19 2025.2

Prediction of induced fluxes in reverse nonequilibrium molecular dynamics. Reviewed International journal

Oishi T, Koide Y, Ishida T, Masubuchi Y, Uneyama T

The Journal of chemical physics Vol. 162 ( 5 ) 2025.2

Coarse-Grained Simulation Model for Crystalline Polymer Solids by Using Breakable Bonds Reviewed International journal

Uneyama T

The Journal of Physical Chemistry B Vol. 129 ( 1 ) page： 506 - 523 2024.12

Reverse Nonequilibrium Molecular Dynamics Simulations of a Melt of Kremer-Grest Type Model under Fast Shear. Reviewed International coauthorship International journal

Oishi T, Koide Y, Ishida T, Uneyama T, Masubuchi Y, Müller-Plathe F

Journal of chemical theory and computation Vol. 20 ( 21 ) page： 9666 - 9672 2024.10

Normal Modes of Rouse-Ham Symmetric Star Polymer Model Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 52 ( 4 ) page： 255 - 263 2024.9

Phantom chain simulations for the fracture of star polymer networks with various strand densities. Reviewed International journal

Masubuchi Y, Ishida T, Koide Y, Uneyama T

Soft matter 2024.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Soft Matter

Despite many attempts, the relationship between the fracture and structure of polymer networks is yet to be clarified. For this problem, a recent study on phantom chain simulations [Y. Masubuchi et al., Macromolecules, 2023, 56, 9359-9367.] has demonstrated that the fracture characteristics obtained for polymer networks with various node functionalities and conversion ratios lie on master curves if they are plotted against cycle rank, which is the number of closed loops in the network per network node. In this study, we extended the simulation to the effect of prepolymer concentration c on the relationships between the cycle rank and fracture characteristics within the concentration range of 1 ≲ c/c* ≲ 10, concerning the overlapping concentration c*. We created networks from sols of star-branched phantom bead-spring chains via an end-linking reaction between different chains through Brownian dynamics simulations upon varying the number of branching arms f from 1 to 8, and the conversion ratio φc from 0.6 to 0.95. For the resultant networks, the cycle rank ξ was consistent with the mean-field theory. The networks were uniaxially stretched with energy minimization until break to obtain modulus G, strain at break ϵb, stress at break σb, and work for fracture Wb. As reported earlier, ϵb data for various f and φc are located on a master curve if plotted against ξ. The other quantities also draw master curves as functions of ξ if normalized by the branch point density υbr. The master curves depend on c; as c increases, all the mechanical characteristics monotonically increase. If we plot σb/υbr and Wb/υbr against G/υbr, the data for various f and φc lie on master curves but depending on c. Consequently, the fracture characteristics are not solely described by the modulus.

DOI： 10.1039/d4sm00726c

Scopus

PubMed

Effect of Mass on Single File Diffusion Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 52 ( 3 ) page： 171 - 179 2024.6

Dissipative Particle Dynamics Simulation Plus Slip-Springs for Entangled Polymers with Various Slip-Spring Densities Reviewed International coauthorship International journal

Masubuchi Y., Guo H., Wang F., Khomami B., Boudaghi-Khajehnobar M., Doi Y., Ishida T., Uneyama T.

Macromolecules Vol. 57 ( 10 ) page： 4867 - 4877 2024.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Macromolecules

Slip-spring models are valuable tools for simulating entangled polymers, bridging the gap between bead-spring models with excluded volume and network models with presumed reptation motion. This study focuses on the DPD-SS (Dissipative Particle Dynamics-Slip-Spring) model, which introduces slip springs into the standard DPD polymer model with soft-core interactions. By systematically adjusting the activity of slip springs, the density of slip springs within the system is varied. Simulation results demonstrate the compatibility of models with different slip-spring densities in terms of diffusion and linear relaxation modulus when the average number of slip springs per chain is the same. The conversion between DPD-SS models concerning length and time is achieved through Rouse scaling, which utilizes the average number of DPD beads between consecutive anchoring points of slip springs. Additionally, the modulus conversion is accomplished through the plateau modulus that takes account of fluctuations around entanglement. Notably, diffusion and relaxation modulus from the DPD-SS model align with those reported for standard Kremer-Grest and DPD models featuring strong repulsive interactions.

DOI： 10.1021/acs.macromol.4c00280

Scopus

過剰量のシランカップリング剤による鉄粒子の表面処理が MR 流体のレオロジー特性に与える影響 Reviewed

山脇悠矢, 石田崇人, 土肥侑也, 畝山多加志, 増渕雄一

日本レオロジー学会誌 Vol. 52 ( 2 ) page： 99 - 105 2024.4

Comparison of Linear Viscoelastic Behaviors of Langevin- and Jump-Rouse Models Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 52 ( 1 ) page： 27 - 35 2024.2

Coarse-grained molecular dynamics simulation of oxidative aging of polymers -effect of free radical diffusivity - Reviewed International journal

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

Polymer Journal Vol. 56 page： 1069 - 1078 2024

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

Recently, we developed an oxidative aging simulation technique that explicitly considers the transport of radicals by combining oxidation kinetics with coarse-grained molecular dynamics [1]. The current study explores the role of the free radical diffusivity of oxidative aging in polymers, with a focus on its effects on the heterogeneity of spatiotemporal structures and reaction kinetics, through coarse-grained simulations. By examining two distinct systems, including a heterosystem with a high reaction rate and a quasi-homosystem with a low reaction rate, we investigated how the diffusivity of free radicals influences the oxidative aging process. We examined three different diffusivity levels of radicals. For the slowest case, the radical diffusivity is slightly faster than that of the single polymer segment, whereas for the fastest case, the radical diffuses infinitely faster than the polymers. The aging simulations revealed that the variations in free radical diffusivity quantitatively change the reaction kinetics and spatiotemporal structures without qualitatively altering the overall aging behavior. Specifically, in a heterosystem, lower radical diffusivity slows the oxidation kinetics by increasing fluctuations in the local conversion ratios. In contrast, in a quasi-homosystem, reduced radical diffusivity slightly amplifies the heterogeneity of structures in the early aging stages; however, in a high-conversion region, the aged state becomes homogeneous regardless of the degree of radical diffusivity.

DOI： 10.1038/s41428-024-00942-5

Scopus

Brownian simulations for fracture of star polymer phantom networks Reviewed International journal

Masubuchi Y., Koide Y., Ishida T., Uneyama T.

Polymer Journal 2024

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

According to a recent simulation study [Masubuchi et al., Macromolecules, 56, 9359 (2023)], the cycle rank plays a significant role in determining the fracture characteristics of network polymers. However, the previous studies considered only energy-minimized networks without including the effects of thermal agitation. To address this gap, this study conducted Brownian dynamics simulations at various stretch rates. The results showed that even with Brownian motion, the strain and stress at break obtained for different node functionalities and conversion ratios exhibited master curves when plotted versus the cycle rank. These master curves depend on the strain rate, indicating that the strain and stress at break decrease with decreasing strain rate. The curves are qualitatively similar to those observed in energy-minimized simulations, even though the competition among Brownian motion, elongation, and bond scission affects the fracture process.

DOI： 10.1038/s41428-024-00992-9

Scopus

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

Takato Ishida, Yuya Doi, Takashi Uneyama, and Yuichi Masubuchi

Macromolecules 2023.11

Percolation-induced gel-gel phase separation in a dilute polymer network. Reviewed

Shohei Ishikawa, Yasuhide Iwanaga, Takashi Uneyama, Xiang Li, Hironori Hojo, Ikuo Fujinaga, Takuya Katashima, Taku Saito, Yasushi Okada, Ung-il Chung, Naoyuki Sakumichi and Takamasa Sakai

Nature Materials Vol. 22 ( 12 ) page： 1564 - 1570 2023.10

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

Tatsuma Oishi, Yuya Doi, Yuichi Masubuchi, and Takashi Uneyama

Molecular Simulation Vol. 50 ( 1 ) page： 20 - 25 2023.10

Brownian yet non-Gaussian diffusion of a light particle in heavy gas: Lorentz-gas-based analysis Reviewed

Nakai F., Uneyama T.

Physical Review E Vol. 108 ( 4 ) page： 044129 2023.10

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

Non-Gaussian diffusion was recently observed in a gas mixture with mass and fraction contrast [F. Nakai, Phys. Rev. E 107, 014605 (2023)2470-004510.1103/PhysRevE.107.014605]. The mean-square displacement of a minor gas particle with a small mass is linear in time, while the displacement distribution deviates from the Gaussian distribution, which is called the Brownian yet non-Gaussian diffusion. In this work, we theoretically analyze this case where the mass contrast is sufficiently large. Major heavy particles can be interpreted as immobile obstacles, and a minor light particle behaves like a Lorentz gas particle within an intermediate timescale. Despite the similarity between the gas mixture and the conventional Lorentz gas system, the Lorentz gas description cannot fully describe the Brownian yet non-Gaussian diffusion. A successful description can be achieved through a canonical ensemble average of the statistical quantities of the Lorentz gas over the initial speed. Furhter, we show that the van Hove correlation function has a nonexponential tail, which is contrary to the exponential tail observed in various systems.

DOI： 10.1103/PhysRevE.108.044129

Scopus

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

Enomoto, K; Ishida, T; Doi, Y; Uneyama, T; Masubuchi, Y

International Journal for Numerical Methods in Fluids Vol. 96 ( 2 ) page： 125 - 137 2023.9

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

Masubuchi, Y; Doi, Y; Ishida, T; Sakumichi, N; Sakai, T; Mayumi, K; Satoh, K; Uneyama, T

Macromolecules Vol. 56 ( 23 ) page： 9358 - 9367 2023.9

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

Masubuchi Yuichi, Doi Yuya, Ishida Takato, Uneyama Takashi

Nihon Reoroji Gakkaishi Vol. 51 ( 4 ) page： 211 - 217 2023.9

Authorship：Last 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

CiNii Research

Estimating Relaxation Times from a Single Trajectory Reviewed

Takuma Akimoto, Eiji Yamamoto, and Takashi Uneyama

Journal of Physical Society of Japan Vol. 92 ( 7 ) page： 074005-1 - 074005-8 2023.6

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

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

Polymer Journal 2023.5

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

Two-dimensional sheet-shaped poly(methyl methacrylate) (2d-PMMA) with crosslinking only in the two-dimensional direction was synthesized via planar polymerization of MMA monomer in montmorillonite (MMT) nanolayers by using γ-ray irradiation, and the samples obtained were characterized. Size-exclusion chromatography with a multi-angle light scattering (SEC-MALS) measurements of the obtained sample showed bimodal peaks: a main peak with a longer elution time and an apparent molecular weight M w,app and radius of gyration R g in tetrahydrofuran (THF) similar to those for linear PMMA samples, and a subpeak with a shorter elution time and M w,app and R g evidently lower than those for the linear PMMA samples. This result indicated that polymers with moderate branching and crosslinking were contained in the subpeak. Atomic force microscopy (AFM) observation of the sample showed the presence of sheet-shaped molecules with a height of ca. 0.6 nm, corresponding to the thickness of one MMA monomer, and a width of several to several tens of nanometers, showing a broad distribution in molecular width. The subpeak portion was isolated via SEC fractionation, and its AFM observation showed thin circular disk-shaped molecules with relatively uniform size (i.e., a width of several tens of nanometers). However, in these molecules, two types of molecular heights (i.e., 0.6 and 1.2 nm) were identified. This result indicated that MMA monomers were filled as two layers within one MMT interlayer, and the polymerization reaction proceeded in that state. The similarity in the molecular size of 2d-PMMA observed via AFM and SEC-MALS was confirmed. These results demonstrated that the desired sheet-shaped polymers were obtained through the above synthesis and fractionation process.

DOI： 10.1038/s41428-023-00795-4

Web of Science

Scopus

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

Nakai F, Kröger M, Ishida T, Uneyama T, Doi Y, Masubuchi Y

Physical Review E Vol. 107 ( 4 ) page： 044604 2023.4

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

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

Scopus

PubMed

Fluctuating diffusivity emerges even in binary gas mixtures Reviewed

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

Physical Review E Vol. 107 ( 1 ) page： 014605-1 - 014605-9 2023.1

Authorship：Corresponding author 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

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

2023

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

Oishi T., Doi Y., Masubuchi Y., Uneyama T.

Molecular Simulation 2023

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

In some binary fluids, mass transport is observed under a temperature gradient. This phenomenon is called the Soret effect. In this study, we discuss the influence of inter-particle interaction. We considered equimolar binary Lennard–Jones fluids with a mass contrast, whereas the interaction was common for all the particle pairs with various cut-off lengths. We performed molecular dynamics simulations of such fluids under equilibrium to obtain the cross-transport coefficients (Formula presented.) between the fluxes of mass and heat. The simulation revealed that this quantity strongly depends on the cut-off length. Further, we decomposed the heat flux into kinetic and potential contributions and calculated the cross-correlations between decomposed fluxes and the mass flux. The result indicates that the potential contribution dominates (Formula presented.), implying that the Soret coefficient is altered by the inter-particle interaction.

DOI： 10.1080/08927022.2023.2268730

Scopus

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

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

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

Stress Tensor of Single Rigid Dumbbell by Virtual Work Method Reviewed

T. Uneyama and T. Oishi and T. Ishida and Y. Doi and Y. Masubu chi

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

Coarse-Grained Modeling of Soft Materials by using Transient Potentials

Uneyama Takashi

Journal of the Society of Materials Science, Japan Vol. 71 ( 8 ) page： 666 - 671 2022.8

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

Soft matters often exhibit complex random motions (Brownian motions) at the mesoscopic scale. Due to the internal degrees of freedom and interaction, the mesoscopic dynamics can be rather complex. To describe such complex dynamics, we need to reduce the degrees of freedom of target systems (the coarse-graining). Conventionally, the projection operator method and the generalized Langevin equation have been utilized to describe such dynamics. Recently, other coarse-graining methods have been proposed where the diffusion coefficients and potentials are treated as time-dependent and fluctuating quantities. The fluctuating diffusion coefficients and potentials enable us to express complex random dynamics of soft matters with relatively simple dynamic equation models. We show basic concepts and some applications of fluctuating diffusion coefficients and potentials.

DOI： https://doi.org/10.2472/jsms.71.666

Linear Response Theory of Scale-Dependent Viscoelasticity for Overdamped Brownian Particle Systems Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 50 ( 3 ) page： 275 - 286 2022.6

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

Masubuchi Y, Yamazaki R, Doi Y, Uneyama T, Sakumichi N, Sakai T

Soft matter 2022.6

Application of projection operator method to coarse-grained dynamics with transient potential Reviewed

Uneyama T.

Physical Review E Vol. 105 ( 4 ) 2022.4

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Review E

We show that the coarse-grained dynamics model with the time-dependent and fluctuating potential (transient potential) can be derived from the microscopic Hamiltonian dynamics. The concept of the transient potential was first introduced rather phenomenologically, and its relation to the underlying microscopic dynamics has not been clarified yet. This is in contrast to the generalized Langevin equation, the relation of which to the microscopic dynamics is well-established. In this work, we show that the dynamic equations with the transient potential can be derived for the coupled oscillator model, without any approximations. It is known that the dynamics of the coupled oscillator model can be exactly described by the generalized Langevin-type equations. This fact implies that the dynamic equations with the transient potential can be utilized as a coarse-grained dynamics model in a similar way to the generalized Langevin equation. Then we show that the dynamic equations for the transient potential can also be formally derived for the microscopic Hamiltonian dynamics, without any approximations. We use the projection operator method for the coarse-grained variables and transient potential. The dynamic equations for the coarse-grained positions and momenta are similar to those in the Hamiltonian dynamics, but the interaction potential is replaced by the transient potential. The dynamic equation for the transient potential is the generalized Langevin equation with the memory effect. Our result justifies the use of the transient potential to describe the coarse-grained dynamics. We propose several approximations to obtain the simplified dynamics model. We show that, under several approximations, the dynamic equation for the transient potential reduces to the relatively simple Markovian dynamic equation for the potential parameters. We also show that with several additional approximations, the approximate dynamics model further reduces to the Markovian Langevin-type equations with the transient potential.

DOI： 10.1103/PhysRevE.105.044117

Scopus

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

Journal of Physical Chemistry B 2022.3

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

Lixin Yang, Takashi Uneyama, Yuichi Masubuchi, Yuya Doi

Nihon Reoroji Gakkaishi Vol. 50 ( 1 ) page： 127 - 135 2022.2

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

Masubuchi Y, Yang L, Uneyama T, Doi Y

Polymers Vol. 14 ( 4 ) 2022.2

高分子の統計力学的取り扱い

畝山多加志

高分子 Vol. 71 page： 614 - 616 2022

Radial Distribution Functions of Entanglements in Primitive Chain Network Simulations Reviewed

Masubuchi Yuichi, Kida Takumitsu, Doi Yuya, Uneyama Takashi

Vol. 49 ( 5 ) page： 337 - 345 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：一般社団法人日本レオロジー学会

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

A New Viewpoint for Complex Dynamics―Time-Dependent and Fluctuating Potentials and Diffusion Coefficients

Uneyama Takashi

Butsuri Vol. 76 ( 10 ) page： 663 - 668 2021.10

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

DOI： 10.11316/butsuri.76.10_663

Linear Rheological Properties of Poly(Propylene Carbonate) with Different Molecular Weights Reviewed

Lixin Yang, Takashi Uneyama, Yuichi Masubuchi, Yuya Doi

Nihon Reoroji Gakkaishi Vol. 49 ( 4 ) page： 267 - 274 2021.9

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

Kida T., Doi Y., Tanaka R., Uneyama T., Shiono T., Masubuchi Y.

Rheologica Acta Vol. 60 ( 9 ) page： 511 - 519 2021.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Rheologica Acta

We synthesized model polyethylene (PE) samples with nearly monodispersed molecular weight distribution and different fractions of short-chain branches to investigate the influences of the branch structure on the rheological properties. The activation energy of the flow process showed linear relations with the weight fractions of comonomer and the short-chain branch. These results suggest that the friction of the chain motion is dominated by the amount of the short-chain branch. The zero-shear viscosity showed a power law to Mw with an exponent of about 3.3 for all linear and branched PEs. The branched PEs showed large entanglement molecular weights compared with the linear PEs because the introduction of the short-chain branches results in the increase of the average molecular weight per backbone unit. Moreover, the introduction of the short-chain branches has no influence on the strain-hardening under an extensional elongation process, indicating that the short-chain branches only affect the friction.

DOI： 10.1007/s00397-021-01286-0

Scopus

Linear Viscoelasticity of Dumbbells Interacting via Gaussian Soft-Core Potential Reviewed

Takashi Uneyama

Nihon Reoroji Gakkaishi Vol. 49 ( 2 ) page： 61 - 71 2021.4

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

Takashi Uneyama and Yuichi Masubuchi

Macromolecules Vol. 54 ( 3 ) page： 1338-1353 2021.1

Short-time dynamics of a tracer in an ideal gas Reviewed

Nakai Fumiaki, Masubuchi Yuichi, Uneyama Takashi

PHYSICAL REVIEW E Vol. 102 ( 3 ) 2020.9

からみあった高分子のメソスケールモデリングの進展 Invited

畝山多加志

分子シミュレーション学会誌 "アンサンブル" Vol. 22 ( 3 ) page： 210-215 2020.7

Primitive chain network simulations for the interrupted shear response of entangled polymeric liquids. Reviewed

Masubuchi Y, Doi Y, Uneyama T

Soft matter Vol. 16 ( 28 ) page： 6654-6661 2020.7

ゆらぐ拡散係数を用いた拡散・緩和現象の記述 Invited

畝山多加志

分子シミュレーション学会誌 "アンサンブル" Vol. 22 ( 2 ) page： 134-141 2020.4

Dissipation in Langevin equation and construction of mobility tensor from dissipative heat flow Reviewed

Uneyama T.

Nihon Reoroji Gakkaishi Vol. 48 ( 2 ) page： 65-78 2020.4

Coarse-graining of microscopic dynamics into a mesoscopic transient potential model Reviewed

Uneyama Takashi

PHYSICAL REVIEW E Vol. 101 ( 3 ) 2020.3

Entanglement Molecular Weight Reviewed

MASUBUCHI Yuichi, DOI Yuya, UNEYAMA Takashi

Nihon Reoroji Gakkaishi Vol. 48 ( 4 ) page： 177-183 2020

高分子の粗視化モデリングとシミュレーション Invited

畝山多加志

日本化学会情報化学部会誌 Vol. 37 ( 4 ) page： 81-86 2019.12

Multi-chain slip-spring simulations for polyisoprene melts Reviewed

Masubuchi Y. and Uneyama T.

Korea Australia Rheology Journal Vol. 31 ( 4 ) page： 241-248 2019.11

Role of Chain Ends in Dynamics of Entangled Polymers Invited

Vol. 68 page： 598-600 2019.10

Effect of Inertia on Linear Viscoelasticity of Harmonic Dumbbell Model Reviewed

Takashi Uneyama, Fumiaki Nakai, and Yuichi Masubuchi

Nihon Reoroji Gakkaishi (J. Soc. Rheol. Jpn.) Vol. 47 ( 4 ) page： 143-154 2019.9

Unveiling diffusive states from center-of-mass trajectories in glassy dynamics. Reviewed

Hachiya Y, Uneyama T, Kaneko T, Akimoto T

The Journal of chemical physics Vol. 151 ( 3 ) page： 034502 2019.7

Brownian motion with alternately fluctuating diffusivity: Stretched-exponential and power-law relaxation Reviewed

Tomoshige Miyaguchi, Takashi Uneyama, and Takuma Akimoto

Physical Review E Vol. 100 ( 1 ) page： 012116 2019.7

Retardation of the reaction kinetics of polymers due to entanglement in the post-gel stage in multi-chain slip-spring simulations. Reviewed

Masubuchi Y, Uneyama T

Soft matter Vol. 15 ( 25 ) page： 5109-5115 2019.6

Relaxation functions of the Ornstein-Uhlenbeck process with fluctuating diffusivity Reviewed

Takashi Uneyama, Tomoshige Miyaguchi, and Takuma Akimoto

Physical Review E Vol. 99 ( 3 ) page： 032127 2019.3

Characterization of critical gel state of polyamides by viscoelastic, thermal, and IR measurements Reviewed

T. Hirayama, T. Uneyama, and Y. Masubuchi

Rheologica Acta Vol. 58 ( 5 ) page： 281-290 2019.3

A Self-Consistent Field Theory Based on a Soft-Dumbbell Model for Symmetric Diblock Copolymers Reviewed

UNEYAMA Takashi

KOBUNSHI RONBUNSHU Vol. 76 ( 1 ) page： 44-51 2019.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We propose a highly coarse-grained, self-consistent field (SCF) theory for simulations of symmetric diblock copolymers, based on the soft dumbbell model. We apply the standard derivation method of the SCF model to the soft dumbbell model, and derive the set of self-consistent equations. We perform the SCF simulations in one dimension, based on the derived model, and show that the SCF model can reproduce microphase separation structures properly. We theoretically consider the properties of the model and discuss possible applications.

DOI： 10.1295/koron.2018-0035

A transient bond model for dynamic constraints in meso-scale coarse-grained systems Reviewed

Takashi Uneyama

Journal of Chemical Physics Vol. 150 ( 1 ) page： 024901 2019.1

Comparison among multi-chain models for entangled polymer dynamics. Reviewed

Masubuchi Y, Uneyama T

Soft matter Vol. 14 ( 29 ) page： 5986-5994 2018.7

Effect of Pore Size Distribution on Compressive Behavior of Moderately Expanded Low-Density Polyethylene Foams Reviewed

Takashi Uneyama, Tatsuya Yamazaki, Toshio Igarashi, and Koh-hei Nitta

Polymer Engineering and Science Vol. 59 ( 3 ) page： 510-518 2018

Transparent Woody Film Made by Dissolution of Finely Divided Japanese Beech in Formic Acid at Room Temperature Reviewed

Nishiwaki-Akine Yuri, Kanazawa Sui, Uneyama Takashi, Nitta Koh-hei, Yamamoto-Ikemoto Ryoko, Watanabe Takashi

ACS SUSTAINABLE CHEMISTRY & ENGINEERING Vol. 5 ( 12 ) page： 11536-11542 2017.12

Orientational cross correlations between entangled branch polymers in primitive chain network simulations Reviewed

Masubuchi Yuichi, Pandey Ankita, Amamoto Yoshifumi, Uneyama Takashi

JOURNAL OF CHEMICAL PHYSICS Vol. 147 ( 18 ) 2017.11

Observing Polymers with Computers: What and How can We do? Invited

Vol. 66 page： 547-548 2017

Constrution of Coarse-Grained Models of Meso-Scale Structures for Dynamics in Polymeric Systems Invited

Vol. 45 page： 217-223 2017

Compressive Behavior of Moderately Expanded Low Density Polyethylene (LDPE) Foams Reviewed

Uneyama Takashi, Honda Tetsuhiro, Igarashi Toshiro, Nitta Koh-hei

NIHON REOROJI GAKKAISHI Vol. 44 ( 1 ) page： 29-38 2016

Fluctuation analysis of time-averaged mean-square displacement for the Langevin equation with time-dependent and fluctuating diffusivity Reviewed

Uneyama Takashi, Miyaguchi Tomoshige, Akimoto Takuma

PHYSICAL REVIEW E Vol. 92 ( 3 ) 2015.9

Self-consistent field model simulations for statistics of amorphous polymer chains in crystalline lamellar structures Reviewed

Uneyama Takashi, Miyata Takafumi, Nitta Koh-hei

JOURNAL OF CHEMICAL PHYSICS Vol. 141 ( 16 ) 2014.10

Linear viscoelasticity of unentangled corona blocks and star arms Reviewed

Chen Quan, Uneyama Takashi

RHEOLOGICA ACTA Vol. 53 ( 9 ) page： 701-714 2014.9

Rheo-Dielectric Responses of Entangled cis-Polyisoprene under Uniform Steady Shear and LAOS Reviewed

Horio Kazushi, Uneyama Takashi, Matsumiya Yumi, Masubuchi Yuichi, Watanabe Hiroshi

MACROMOLECULES Vol. 47 ( 1 ) page： 246-255 2014.1

分子モデル・流動特性・シミュレーション Invited

畝山多加志

成形加工 Vol. 26 page： 452-455 2014

Concentration Dependence of Nonlinear Rheological Properties of Hydrophobically Modified Ethoxylated Urethane Aqueous Solutions Reviewed

Suzuki Shinya, Uneyama Takashi, Watanabe Hiroshi

MACROMOLECULES Vol. 46 ( 9 ) page： 3497-3504 2013.5

高分子からみあい系のミクロ・メソスケール分子モデルの接続 Invited

畝山多加志

分子シミュレーション研究会会誌「アンサンブル」 Vol. 13 page： 112-117 2013

固体基本特性 -- 高分子の結晶ラメラ構造に対する非晶高分子鎖の運動性と統計性の影響 -- Invited

畝山多加志, 新田晃平

成形加工 Vol. 25 page： 327-330 2013

Multi-chain slip-spring model for entangled polymer dynamics Reviewed

Uneyama Takashi, Masubuchi Yuichi

JOURNAL OF CHEMICAL PHYSICS Vol. 137 ( 15 ) 2012.10

Crossover time in relative fluctuations characterizes the longest relaxation time of entangled polymers Reviewed

Uneyama Takashi, Akimoto Takuma, Miyaguchi Tomoshige

JOURNAL OF CHEMICAL PHYSICS Vol. 137 ( 11 ) 2012.9

Concentration dependence of rheological properties of telechelic associative polymer solutions Reviewed

Uneyama Takashi, Suzuki Shinya, Watanabe Hiroshi

PHYSICAL REVIEW E Vol. 86 ( 3 ) 2012.9

A multiscale simulation of polymer processing using parameter-based bridging in melt rheology Reviewed

Masubuchi Yuichi, Uneyama Takashi, Saito Keiichi

JOURNAL OF APPLIED POLYMER SCIENCE Vol. 125 ( 4 ) page： 2740-2747 2012.8

Nonlinear Rheology of Telechelic Associative Polymer Networks: Shear Thickening and Thinning Behavior of Hydrophobically Modified Ethoxylated Urethane (HEUR) in Aqueous Solution Reviewed

Suzuki Shinya, Uneyama Takashi, Inoue Tadashi, Watanabe Hiroshi

MACROMOLECULES Vol. 45 ( 2 ) page： 888-898 2012.1

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism Reviewed

Suzuki Shinya, Uneyama Takashi, Inoue Tadashi, Watanabe Hiroshi

NIHON REOROJI GAKKAISHI Vol. 40 ( 1 ) page： 31-36 2012

Soft-core Interaction Between Entanglement Segments for Primitive Chain Network Simulations Reviewed

Okuda Satoru, Uneyama Takashi, Inoue Yasuhiro, Masubuchi Yuichi, Hojo Masaki

NIHON REOROJI GAKKAISHI Vol. 40 ( 1 ) page： 21-30 2012

Detailed balance condition and effective free energy in the primitive chain network model Reviewed

Uneyama Takashi, Masubuchi Yuichi

JOURNAL OF CHEMICAL PHYSICS Vol. 135 ( 18 ) 2011.11

Numerical study of chain conformation on shear banding using diffusive Rolie-Poly model Reviewed

Chung Changkwon, Uneyama Takashi, Masubuchi Yuichi, Watanabe Hiroshi

RHEOLOGICA ACTA Vol. 50 ( 9-10 ) page： 753-766 2011.10

Equilibrium Statistics of Weakly Slip-Linked Gaussian Polymer Chains Reviewed

Uneyama Takashi, Horio Kazushi

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS Vol. 49 ( 13 ) page： 966-977 2011.7

Anisotropic mobility model for polymers under shear and its linear response functions Reviewed

Uneyama Takashi, Horio Kazushi, Watanabe Hiroshi

PHYSICAL REVIEW E Vol. 83 ( 6 ) 2011.6

Optimization of the Multishift QR Algorithm with Coprocessors for Non-Hermitian Eigenvalue Problems Reviewed

Miyata Takafumi, Yamamoto Yusaku, Uneyama Takashi, Nakamura Yoshimasa, Zhang Shao-Liang

EAST ASIAN JOURNAL ON APPLIED MATHEMATICS Vol. 1 ( 2 ) page： 187-196 2011.5

A Note for Kohlrausch-Williams-Watts Relaxation Function Reviewed

Kawasaki Yohji, Watanabe Hiroshi, Uneyama Takashi

NIHON REOROJI GAKKAISHI Vol. 39 ( 3 ) page： 127-131 2011

Single Chain Slip-Spring Model for Fast Rheology Simulations of Entangled Polymers on GPU Reviewed

Uneyama Takashi

NIHON REOROJI GAKKAISHI Vol. 39 ( 4 ) page： 135-152 2011

Structure of entangled polymer network from primitive chain network simulations Reviewed

Masubuchi Yuichi, Uneyama Takashi, Watanabe Hiroshi, Ianniruberto Giovanni, Greco Francesco, Marrucci Giuseppe

JOURNAL OF CHEMICAL PHYSICS Vol. 132 ( 13 ) 2010.4

からみあった高分子のレオロジーの分子理論 Invited

畝山多加志

高分子 Vol. 60 page： 199-200 2010

Primitive chain network simulations for entangled DNA solutions Reviewed

Masubuchi Yuichi, Furuichi Kenji, Horio Kazushi, Uneyama Takashi, Watanabe Hiroshi, Ianniruberto Giovanni, Greco Francesco, Marrucci Giuseppe

JOURNAL OF CHEMICAL PHYSICS Vol. 131 ( 11 ) 2009.9

A Theoretical Analysis of Rheodielectric Response of Type-A Polymer Chains Reviewed

Uneyama Takashi, Masubuchi Yuichi, Horio Kazushi, Matsumiya Yumi, Watanabe Hiroshi, Pathak Jai A., Roland C. Michael

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS Vol. 47 ( 11 ) page： 1039-1057 2009.6

Coarse-Grained Brownian Dynamics Simulations for Symmetric Diblock Copolymer Melts Based on the Soft Dumbbell Model Reviewed

Uneyama Takashi

NIHON REOROJI GAKKAISHI Vol. 37 ( 2 ) page： 81-90 2009

Primitive Chain Network Simulations of Conformational Relaxation for Individual Molecules in the Entangled State. II. Retraction from Stretched States Reviewed

Masubuchi Yuichi, Uneyama Takashi, Watanabe Hiroshi, Ianniruberto Giovanni, Greco Francesco, Marrucci Giuseppe

NIHON REOROJI GAKKAISHI Vol. 37 ( 2 ) page： 65-68 2009

正方行列向け特異値分解のCUDAによる高速化 Reviewed

深谷猛, 山本有作, 畝山多加志, 中村佳正

情報処理学会論文誌論文誌 (トランザクション) コンピューティング Vol. 2 ( 2 ) page： 98-109 2009

ある在庫管理計画問題の動的計画法による解法とCUDAを用いた高速化 Reviewed

李天, 河畠工, 山本有作, 畝山多加志, 張紹良

情報処理学会論文誌論文誌 (トランザクション) コンピューティング Vol. 1 ( 2 ) page： 221-230 2008

Density functional simulation of spontaneous formation of vesicle in block copolymer solutions Reviewed

Uneyama Takashi

JOURNAL OF CHEMICAL PHYSICS Vol. 126 ( 11 ) 2007.3

Accelerating the singular value decomposition of rectangular matrices with the CSX600 and the integrable SVD Reviewed

Yamamoto Yusaku, Fukaya Takeshi, Uneyama Takashi, Takata Masami, Kimura Kinji, Iwasaki Masashi, Nakamura Yoshimasa

PARALLEL COMPUTING TECHNOLOGIES, PROCEEDINGS Vol. 4671 page： 340-+ 2007

長方行列向け特異値分解の浮動小数点コプロセッサによる高速化 Reviewed

深谷猛, 山本有作, 畝山多加志, 堀玄, 梅野健

情報処理学会論文誌論文誌 (トランザクション) コンピューティング Vol. 48 ( SIG8 ) page： 31-43 2007

Calculation of the Micellar Structure of Polymer Surfactant on the Basis of the Density Functional Theory Reviewed

Takashi Uneyama, Masao Doi

Macromolecules Vol. 38 ( 13 ) page： 5817-5825 2005.5

Density Functional Theory for Block Copolymer Melts and Blends Reviewed

Takashi Uneyama, Masao Doi

Macromolecules Vol. 38 ( 1 ) page： 196-205 2004.12

　 PREV - NEXT 　

<UNEYAMA Takashi>

Papers - UNEYAMA Takashi