研究者詳細 - 畝山　多加志

論文 - 畝山　多加志

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Coarse-grained molecular dynamics simulations for oxidative aging of polymers under various O₂ concentrations 査読有り国際誌 Open Access

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

Polymer Degradation and Stability 239 巻 2025年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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. 査読有り国際誌

Koide Y, Ishida T, Uneyama T, Masubuchi Y

The Journal of chemical physics 162 巻 ( 17 ) 2025年5月

Radius of Gyration in Shear Gradient Direction Governs Steady Shear Viscosity of Rouse-Type Model 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 53 巻 ( 1 ) 頁： 11 - 19 2025年2月

Prediction of induced fluxes in reverse nonequilibrium molecular dynamics. 査読有り国際誌

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

The Journal of chemical physics 162 巻 ( 5 ) 2025年2月

Coarse-Grained Simulation Model for Crystalline Polymer Solids by Using Breakable Bonds 査読有り国際誌

Uneyama T

The Journal of Physical Chemistry B 129 巻 ( 1 ) 頁： 506 - 523 2024年12月

Reverse Nonequilibrium Molecular Dynamics Simulations of a Melt of Kremer-Grest Type Model under Fast Shear. 査読有り国際共著国際誌

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

Journal of chemical theory and computation 20 巻 ( 21 ) 頁： 9666 - 9672 2024年10月

Normal Modes of Rouse-Ham Symmetric Star Polymer Model 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 52 巻 ( 4 ) 頁： 255 - 263 2024年9月

Phantom chain simulations for the fracture of star polymer networks with various strand densities. 査読有り国際誌

Masubuchi Y, Ishida T, Koide Y, Uneyama T

Soft matter 2024年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 52 巻 ( 3 ) 頁： 171 - 179 2024年6月

Dissipative Particle Dynamics Simulation Plus Slip-Springs for Entangled Polymers with Various Slip-Spring Densities 査読有り国際共著国際誌

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

Macromolecules 57 巻 ( 10 ) 頁： 4867 - 4877 2024年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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査読有り

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 52 巻 ( 2 ) 頁： 99 - 105 2024年4月

Comparison of Linear Viscoelastic Behaviors of Langevin- and Jump-Rouse Models 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 52 巻 ( 1 ) 頁： 27 - 35 2024年2月

Coarse-grained molecular dynamics simulation of oxidative aging of polymers -effect of free radical diffusivity - 査読有り国際誌

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

Polymer Journal 56 巻頁： 1069 - 1078 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り国際誌

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

Polymer Journal 2024年

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

Macromolecules 2023年11月

Percolation-induced gel-gel phase separation in a dilute polymer network. 査読有り

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 22 巻 ( 12 ) 頁： 1564 - 1570 2023年10月

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

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

Molecular Simulation 50 巻 ( 1 ) 頁： 20 - 25 2023年10月

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

Nakai F., Uneyama T.

Physical Review E 108 巻 ( 4 ) 頁： 044129 2023年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

International Journal for Numerical Methods in Fluids 96 巻 ( 2 ) 頁： 125 - 137 2023年9月

Phantom-Chain Simulations for the Effect of Node Functionality on the Fracture of Star-Polymer Networks 査読有り国際誌

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

Macromolecules 56 巻 ( 23 ) 頁： 9358 - 9367 2023年9月

A Multi-Chain Slip-Spring Model without the Slip-Spring Degeneracy 査読有り

Masubuchi Yuichi, Doi Yuya, Ishida Takato, Uneyama Takashi

Nihon Reoroji Gakkaishi 51 巻 ( 4 ) 頁： 211 - 217 2023年9月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

Takuma Akimoto, Eiji Yamamoto, and Takashi Uneyama

Journal of Physical Society of Japan 92 巻 ( 7 ) 頁： 074005-1 - 074005-8 2023年6月

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

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

Polymer Journal 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り国際共著

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

Physical Review E 107 巻 ( 4 ) 頁： 044604 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

Physical Review E 107 巻 ( 1 ) 頁： 014605-1 - 014605-9 2023年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

2023年

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

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

Molecular Simulation 2023年

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

Nihon Reoroji Gakkaishi 50 巻 ( 4 ) 頁： 305 - 312 2022年9月

Stress Tensor of Single Rigid Dumbbell by Virtual Work Method 査読有り

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

Nihon Reoroji Gakkaishi 50 巻 ( 4 ) 頁： 313 - 322 2022年9月

過渡ポテンシャルを用いたソフトマテリアルの粗視化モデリング

畝山多加志

材料 71 巻 ( 8 ) 頁： 666 - 671 2022年8月

担当区分：筆頭著者,　最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本物理学会

物性の研究ではマクロスケールの（巨視的な）物性について測定や解析が行われることが多い．マクロスケールの物質の示す複雑な緩和や応答も元をたどれば究極的にはミクロスケールの（微視的な）分子や原子の構造に還元できると期待される．これは物理（特に統計力学）の考え方としては標準的なものであろう．ソフトマターのように構成要素が複雑な場合には，ミクロスケールとマクロスケールの中間であるメソスケールにおいて特徴的な構造や運動をもつことがある．この場合もやはりメソスケールの挙動は究極的にはミクロスケールに還元できると考えられる．原理的には分子や原子の初期状態の位置と運動量がわかれば系の時間発展は一意に決まるのだから，メソスケールだろうとマクロスケールだろうとミクロスケールの情報からすべて計算が可能なように思える．もちろん，初期状態を完全に知ることはできないし，カオス的な振る舞いもあるため状況はそこまで単純ではない．メソスケールの運動や緩和，あるいはメソスケールの情報を強く反映するマクロスケールの物性を理解するには，メソスケールの運動を直接的に記述し解析することが望ましい．これはミクロスケールの情報のうち興味ある一部の情報（着目する粒子の位置や運動量）のみを取り出す粗視化とよばれる手法を用いて実現できる．粗視化によって消える自由度の効果は系統的に取り込め，未知の初期状態の影響はランダムな揺動力という形で運動方程式中に現れる．このランダムな揺動力がBrown運動の起源となり，粒子の運動の軌跡は不規則な形状を呈することになる．さらに，粒子の感じるポテンシャルや時間遅れの効果等を取り込むことで，メソスケールの運動の一般的記述が可能になるとされている．ところが，このような手法で十分に一般的なメソスケールの運動を記述可能かというと，実はそうではない．既存の手法で記述不可能な対象が少なからず存在するのである．例えば，高分子の運動は分子同士が互いにすり抜けられないという動的な拘束のために単純な形では記述できない．近年，そのようなある種の特殊なBrown運動の記述について，新しい視点からのモデル化や理解が進展しつつある．メソスケールの系を記述する際に通常着目する自由度である位置や運動量に加えて，拡散係数やポテンシャルといった量も自由度として考慮するというものである．従来の方法では，拡散係数やポテンシャルは環境の効果を平均化したものであり，平均値からのずれがランダムな揺動力として取り扱われていた．これに対して，新しい方法では，拡散係数やポテンシャル自体が時々刻々と変化する環境の影響を受けてランダムに変化する量であるとする．一見，ランダムに変化する部分が変わっただけでさほどの影響がないように思えるかもしれないが，ゆらぐ拡散係数やポテンシャルを使うことで従来の方法とは定性的に異なる運動を記述することができる．ゆらぐ拡散係数やポテンシャルを用いた新しい方法は新しい運動方程式のクラスを形成しているものと考えられる．新しい方法はソフトマターをはじめとしたさまざまな系に適用できるものと期待される．例えば，高分子の動的な拘束を表現するために各論的・現象論的にさまざまな運動モデルが提案されているが，これらをゆらぐ拡散係数やポテンシャルを使った枠組みで統一的に解釈し直すことができる．また，過冷却液体中の分子の示す一時的にトラップされるような運動も，新しい方法を用いることで単純な形で記述することができる．

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

Linear Response Theory of Scale-Dependent Viscoelasticity for Overdamped Brownian Particle Systems 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 50 巻 ( 3 ) 頁： 275 - 286 2022年6月

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

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

Soft matter 2022年6月

Application of projection operator method to coarse-grained dynamics with transient potential 査読有り

Uneyama T.

Physical Review E 105 巻 ( 4 ) 2022年4月

担当区分：筆頭著者,　最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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. 査読有り

Journal of Physical Chemistry B 2022年3月

Nonlinear Shear and Elongational Rheology of Poly(propylene carbonate) 査読有り

Lixin Yang, Takashi Uneyama, Yuichi Masubuchi, Yuya Doi

Nihon Reoroji Gakkaishi 50 巻 ( 1 ) 頁： 127 - 135 2022年2月

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

Masubuchi Y, Yang L, Uneyama T, Doi Y

Polymers 14 巻 ( 4 ) 2022年2月

高分子の統計力学的取り扱い

畝山多加志

高分子 71 巻頁： 614 - 616 2022年

Radial Distribution Functions of Entanglements in Primitive Chain Network Simulations 査読有り

Masubuchi Yuichi, Kida Takumitsu, Doi Yuya, Uneyama Takashi

49 巻 ( 5 ) 頁： 337 - 345 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

複雑な運動の新しい見方――時間に依存してゆらぐポテンシャルと拡散係数

畝山多加志

日本物理学会誌 76 巻 ( 10 ) 頁： 663 - 668 2021年10月

担当区分：筆頭著者,　最終著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本物理学会

DOI： 10.11316/butsuri.76.10_663

Linear Rheological Properties of Poly(Propylene Carbonate) with Different Molecular Weights 査読有り

Lixin Yang, Takashi Uneyama, Yuichi Masubuchi, Yuya Doi

Nihon Reoroji Gakkaishi 49 巻 ( 4 ) 頁： 267 - 274 2021年9月

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

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

Rheologica Acta 60 巻 ( 9 ) 頁： 511 - 519 2021年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

Takashi Uneyama

Nihon Reoroji Gakkaishi 49 巻 ( 2 ) 頁： 61 - 71 2021年4月

Plateau Moduli of Several Single-Chain Slip-Link and Slip-Spring Models 査読有り

Takashi Uneyama and Yuichi Masubuchi

Macromolecules 54 巻 ( 3 ) 頁： 1338-1353 2021年1月

Short-time dynamics of a tracer in an ideal gas 査読有り

Nakai Fumiaki, Masubuchi Yuichi, Uneyama Takashi

PHYSICAL REVIEW E 102 巻 ( 3 ) 2020年9月

からみあった高分子のメソスケールモデリングの進展招待有り

畝山多加志

分子シミュレーション学会誌 "アンサンブル" 22 巻 ( 3 ) 頁： 210-215 2020年7月

Primitive chain network simulations for the interrupted shear response of entangled polymeric liquids. 査読有り

Masubuchi Y, Doi Y, Uneyama T

Soft matter 16 巻 ( 28 ) 頁： 6654-6661 2020年7月

ゆらぐ拡散係数を用いた拡散・緩和現象の記述招待有り

畝山多加志

分子シミュレーション学会誌 "アンサンブル" 22 巻 ( 2 ) 頁： 134-141 2020年4月

Dissipation in Langevin equation and construction of mobility tensor from dissipative heat flow 査読有り

Uneyama T.

Nihon Reoroji Gakkaishi 48 巻 ( 2 ) 頁： 65-78 2020年4月

Coarse-graining of microscopic dynamics into a mesoscopic transient potential model 査読有り

Uneyama Takashi

PHYSICAL REVIEW E 101 巻 ( 3 ) 2020年3月

Entanglement Molecular Weight 査読有り

MASUBUCHI Yuichi, DOI Yuya, UNEYAMA Takashi

Nihon Reoroji Gakkaishi 48 巻 ( 4 ) 頁： 177-183 2020年

高分子の粗視化モデリングとシミュレーション招待有り

畝山多加志

日本化学会情報化学部会誌 37 巻 ( 4 ) 頁： 81-86 2019年12月

Multi-chain slip-spring simulations for polyisoprene melts 査読有り

Masubuchi Y. and Uneyama T.

Korea Australia Rheology Journal 31 巻 ( 4 ) 頁： 241-248 2019年11月

からみあった高分子のダイナミクスにおける末端の役割招待有り

畝山多加志

高分子 68 巻頁： 598-600 2019年10月

Effect of Inertia on Linear Viscoelasticity of Harmonic Dumbbell Model 査読有り

Takashi Uneyama, Fumiaki Nakai, and Yuichi Masubuchi

Nihon Reoroji Gakkaishi (J. Soc. Rheol. Jpn.) 47 巻 ( 4 ) 頁： 143-154 2019年9月

Unveiling diffusive states from center-of-mass trajectories in glassy dynamics. 査読有り

Hachiya Y, Uneyama T, Kaneko T, Akimoto T

The Journal of chemical physics 151 巻 ( 3 ) 頁： 034502 2019年7月

Brownian motion with alternately fluctuating diffusivity: Stretched-exponential and power-law relaxation 査読有り

Tomoshige Miyaguchi, Takashi Uneyama, and Takuma Akimoto

Physical Review E 100 巻 ( 1 ) 頁： 012116 2019年7月

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

Masubuchi Y, Uneyama T

Soft matter 15 巻 ( 25 ) 頁： 5109-5115 2019年6月

Relaxation functions of the Ornstein-Uhlenbeck process with fluctuating diffusivity 査読有り

Takashi Uneyama, Tomoshige Miyaguchi, and Takuma Akimoto

Physical Review E 99 巻 ( 3 ) 頁： 032127 2019年3月

Characterization of critical gel state of polyamides by viscoelastic, thermal, and IR measurements 査読有り

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

Rheologica Acta 58 巻 ( 5 ) 頁： 281-290 2019年3月

ソフトダンベルモデルに基づく対称ジブロックコポリマーの自己無撞着場理論査読有り

畝山多加志

高分子論文集 76 巻 ( 1 ) 頁： 44-51 2019年1月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

対称ジブロックコポリマーのミクロ相分離構造を取り扱うための粗視化モデルとして，ソフトダンベルモデルに基づく自己無撞着場(SCF)理論を提案する．二つの粗視化粒子を連結することでジブロックコポリマーを表現するソフトダンベルモデルに対して標準的なSCFモデルの導出手法を適用することで濃度場と外場に対する自己無撞着な連立方程式を導出する．得られたSCFモデルを用いて一次元系でシミュレーションを行うことで，ミクロ相分離構造を再現できることを示す．また，得られたSCFモデルの性質について考察を行う．

DOI： 10.1295/koron.2018-0035

A transient bond model for dynamic constraints in meso-scale coarse-grained systems 査読有り

Takashi Uneyama

Journal of Chemical Physics 150 巻 ( 1 ) 頁： 024901 2019年1月

Comparison among multi-chain models for entangled polymer dynamics. 査読有り

Masubuchi Y, Uneyama T

Soft matter 14 巻 ( 29 ) 頁： 5986-5994 2018年7月

Effect of Pore Size Distribution on Compressive Behavior of Moderately Expanded Low-Density Polyethylene Foams 査読有り

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

Polymer Engineering and Science 59 巻 ( 3 ) 頁： 510-518 2018年

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

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

ACS SUSTAINABLE CHEMISTRY & ENGINEERING 5 巻 ( 12 ) 頁： 11536-11542 2017年12月

Orientational cross correlations between entangled branch polymers in primitive chain network simulations 査読有り

Masubuchi Yuichi, Pandey Ankita, Amamoto Yoshifumi, Uneyama Takashi

JOURNAL OF CHEMICAL PHYSICS 147 巻 ( 18 ) 2017年11月

コンピュータを使ったの高分子の見方: 何ができるか、どうするか招待有り

畝山多加志

高分子 66 巻頁： 547-548 2017年

高分子系ダイナミクスのメソスケール構造粗視化モデルの構築招待有り

畝山多加志

日本レオロジー学会誌 45 巻頁： 217-223 2017年

Compressive Behavior of Moderately Expanded Low Density Polyethylene (LDPE) Foams 査読有り

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

NIHON REOROJI GAKKAISHI 44 巻 ( 1 ) 頁： 29-38 2016年

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

Uneyama Takashi, Miyaguchi Tomoshige, Akimoto Takuma

PHYSICAL REVIEW E 92 巻 ( 3 ) 2015年9月

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

Uneyama Takashi, Miyata Takafumi, Nitta Koh-hei

JOURNAL OF CHEMICAL PHYSICS 141 巻 ( 16 ) 2014年10月

Linear viscoelasticity of unentangled corona blocks and star arms 査読有り

Chen Quan, Uneyama Takashi

RHEOLOGICA ACTA 53 巻 ( 9 ) 頁： 701-714 2014年9月

Rheo-Dielectric Responses of Entangled cis-Polyisoprene under Uniform Steady Shear and LAOS 査読有り

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

MACROMOLECULES 47 巻 ( 1 ) 頁： 246-255 2014年1月

分子モデル・流動特性・シミュレーション招待有り

畝山多加志

成形加工 26 巻頁： 452-455 2014年

Concentration Dependence of Nonlinear Rheological Properties of Hydrophobically Modified Ethoxylated Urethane Aqueous Solutions 査読有り

Suzuki Shinya, Uneyama Takashi, Watanabe Hiroshi

MACROMOLECULES 46 巻 ( 9 ) 頁： 3497-3504 2013年5月

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招待有り

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」 13 巻頁： 112-117 2013年

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 -- 招待有り

畝山多加志, 新田晃平

成形加工 25 巻頁： 327-330 2013年

Multi-chain slip-spring model for entangled polymer dynamics 査読有り

Uneyama Takashi, Masubuchi Yuichi

JOURNAL OF CHEMICAL PHYSICS 137 巻 ( 15 ) 2012年10月

Crossover time in relative fluctuations characterizes the longest relaxation time of entangled polymers 査読有り

Uneyama Takashi, Akimoto Takuma, Miyaguchi Tomoshige

JOURNAL OF CHEMICAL PHYSICS 137 巻 ( 11 ) 2012年9月

Concentration dependence of rheological properties of telechelic associative polymer solutions 査読有り

Uneyama Takashi, Suzuki Shinya, Watanabe Hiroshi

PHYSICAL REVIEW E 86 巻 ( 3 ) 2012年9月

A multiscale simulation of polymer processing using parameter-based bridging in melt rheology 査読有り

Masubuchi Yuichi, Uneyama Takashi, Saito Keiichi

JOURNAL OF APPLIED POLYMER SCIENCE 125 巻 ( 4 ) 頁： 2740-2747 2012年8月

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

Suzuki Shinya, Uneyama Takashi, Inoue Tadashi, Watanabe Hiroshi

MACROMOLECULES 45 巻 ( 2 ) 頁： 888-898 2012年1月

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

Suzuki Shinya, Uneyama Takashi, Inoue Tadashi, Watanabe Hiroshi

NIHON REOROJI GAKKAISHI 40 巻 ( 1 ) 頁： 31-36 2012年

Soft-core Interaction Between Entanglement Segments for Primitive Chain Network Simulations 査読有り

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

NIHON REOROJI GAKKAISHI 40 巻 ( 1 ) 頁： 21-30 2012年

Detailed balance condition and effective free energy in the primitive chain network model 査読有り

Uneyama Takashi, Masubuchi Yuichi

JOURNAL OF CHEMICAL PHYSICS 135 巻 ( 18 ) 2011年11月

Numerical study of chain conformation on shear banding using diffusive Rolie-Poly model 査読有り

Chung Changkwon, Uneyama Takashi, Masubuchi Yuichi, Watanabe Hiroshi

RHEOLOGICA ACTA 50 巻 ( 9-10 ) 頁： 753-766 2011年10月

Equilibrium Statistics of Weakly Slip-Linked Gaussian Polymer Chains 査読有り

Uneyama Takashi, Horio Kazushi

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 49 巻 ( 13 ) 頁： 966-977 2011年7月

Anisotropic mobility model for polymers under shear and its linear response functions 査読有り

Uneyama Takashi, Horio Kazushi, Watanabe Hiroshi

PHYSICAL REVIEW E 83 巻 ( 6 ) 2011年6月

Optimization of the Multishift QR Algorithm with Coprocessors for Non-Hermitian Eigenvalue Problems 査読有り

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

EAST ASIAN JOURNAL ON APPLIED MATHEMATICS 1 巻 ( 2 ) 頁： 187-196 2011年5月

A Note for Kohlrausch-Williams-Watts Relaxation Function 査読有り

Kawasaki Yohji, Watanabe Hiroshi, Uneyama Takashi

NIHON REOROJI GAKKAISHI 39 巻 ( 3 ) 頁： 127-131 2011年

Single Chain Slip-Spring Model for Fast Rheology Simulations of Entangled Polymers on GPU 査読有り

Uneyama Takashi

NIHON REOROJI GAKKAISHI 39 巻 ( 4 ) 頁： 135-152 2011年

Structure of entangled polymer network from primitive chain network simulations 査読有り

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

JOURNAL OF CHEMICAL PHYSICS 132 巻 ( 13 ) 2010年4月

からみあった高分子のレオロジーの分子理論招待有り

畝山多加志

高分子 60 巻頁： 199-200 2010年

Primitive chain network simulations for entangled DNA solutions 査読有り

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

JOURNAL OF CHEMICAL PHYSICS 131 巻 ( 11 ) 2009年9月

A Theoretical Analysis of Rheodielectric Response of Type-A Polymer Chains 査読有り

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

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 47 巻 ( 11 ) 頁： 1039-1057 2009年6月

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

Uneyama Takashi

NIHON REOROJI GAKKAISHI 37 巻 ( 2 ) 頁： 81-90 2009年

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

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

NIHON REOROJI GAKKAISHI 37 巻 ( 2 ) 頁： 65-68 2009年

正方行列向け特異値分解のCUDAによる高速化査読有り

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 2 巻 ( 2 ) 頁： 98-109 2009年

ある在庫管理計画問題の動的計画法による解法とCUDAを用いた高速化査読有り

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 1 巻 ( 2 ) 頁： 221-230 2008年

Density functional simulation of spontaneous formation of vesicle in block copolymer solutions 査読有り

Uneyama Takashi

JOURNAL OF CHEMICAL PHYSICS 126 巻 ( 11 ) 2007年3月

Accelerating the singular value decomposition of rectangular matrices with the CSX600 and the integrable SVD 査読有り

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

PARALLEL COMPUTING TECHNOLOGIES, PROCEEDINGS 4671 巻頁： 340-+ 2007年

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査読有り

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 48 巻 ( SIG8 ) 頁： 31-43 2007年

Calculation of the Micellar Structure of Polymer Surfactant on the Basis of the Density Functional Theory 査読有り

Takashi Uneyama, Masao Doi

Macromolecules 38 巻 ( 13 ) 頁： 5817-5825 2005年5月

Density Functional Theory for Block Copolymer Melts and Blends 査読有り

Takashi Uneyama, Masao Doi

Macromolecules 38 巻 ( 1 ) 頁： 196-205 2004年12月

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