研究者詳細 - 増渕　雄一

論文 - 増渕　雄一

分割表示 236 件中 1 - 20 件目／全件表示 >>

Effects of stirring time on formation of microplastics fragmented from photo-aged polypropylene 査読有り国際誌 Open Access

Haremaki, K; Kida, T; Koide, Y; Uneyama, T; Masubuchi, Y; Ishida, T

MARINE POLLUTION BULLETIN 228 巻頁： 119556 2026年7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：Marine Pollution Bulletin

This paper examines the evolution of microplastic (MP) size distributions fragmented from photo-aged polypropylene (PP) in stirred water. PP specimens fragmented into MPs with their size of 1–30 μm after UV irradiation and stirring in laboratory settings. These laboratory-fragmented MPs were dispersed into the water during the stirring process. A series of MP size distributions was analyzed from optical microscope images of obtained MPs. The MP size distribution was described by an exponential function in the short stirring period, whereas it changed to a power-law function as the stirring time increased. The fragmentation rate of MPs and nanoplastics (NPs) decreased with increasing stirring time. The obtained MP exhibited higher crystallinity than the photo-aged PP specimen after stirring. This result implies that MP fragmentation, as observed under controlled laboratory conditions, is related with the chemi-crystallization of PP.

DOI： 10.1016/j.marpolbul.2026.119556

Effect of flow kinematics on the extensional viscosity of dilute polymer solutions 査読有り国際誌 Open Access

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

Polymer Journal 2026年6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：Polymer Journal

We investigate the effects of flow kinematics on the extensional viscosities of dilute polymer solutions by conducting dissipative particle dynamics simulations under uniaxial, planar, and biaxial extensional flows. At high extension rates, dilute polymer solutions exhibit strain hardening under these flows, whereas the quantitative behavior depends on the flow type. To elucidate the physical origin of this flow-kinematics dependence, we relate the extensional viscosity to the polymer conformation using an analytical expression derived from a single-chain model. The resulting relation allows us to separate the contribution of flow-induced polymer conformational changes and the purely kinematic contribution determined by the structure of the velocity gradient tensor. When polymers remain almost unperturbed by extensional flows, extensional viscosity differences are governed primarily by purely kinematic effects. In contrast, as the polymers are stretched, the gyration radius in the extensional direction becomes the dominant factor, and differences in the degree of stretching in this direction lead to corresponding variations in the extensional viscosity.

DOI： 10.1038/s41428-026-01216-y

Open Access

Scopus

researchmap

Slip-link simulations of long-fiber networks under uniaxial compression 招待有り査読有り国際誌 Open Access

Yuichi Masubuchi

Transport Phenomena 2026年6月

新規シリコーンオイル増粘剤の開発と特性評価査読有り国際誌 Open Access

坂西裕一, 小林弘季, 櫻井優吏, 増渕雄一

日本化粧品技術者会誌 60 巻 ( 2 ) 頁： 81 - 88 2026年6月

担当区分：最終著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：日本化粧品技術者会

シリコーンオイルは，その感触，塗布性，高い透明性から化粧品に広く利用される。しかし，高粘度製剤やゲル化において，他の成分との相溶性や透明性を維持しつつ効果的な増粘を実現することは課題である。本研究は，これら課題を克服し，高い増粘性と優れた透明性を両立する新規シリコーンオイル増粘剤の開発を目的とし，炭化水素鎖を有する新規アミド変性シリコーンを合成した。増粘メカニズム解析の結果，本増粘剤がシリコーンオイル中で逆ミセル様の凝集構造を形成し，シリコーン主鎖を介してネットワーク構造を構築することが示された。このメカニズムにより，ネットワーク内に油性成分が均一に取り込まれ，高い透明性と均質な粘性が実現された。開発した増粘剤は，ジメチルポリシロキサンや環状シリコーンを含む多様なシリコーンオイルに対し，従来の増粘剤では困難であった増粘効果と透明性を同時に付与できることを実証した。これらの知見は，増粘剤設計の新たな指針を提供し，化粧品，医薬品，工業分野における広範な応用可能性を示唆し，シリコーンオイル基盤製剤の進歩に貢献すると考えられる。

DOI： 10.5107/sccj.60.81

Open Access

CiNii Research

Developments in multichain coarse-grained models for entangled polymer dynamics 招待有り査読有り国際誌 Open Access

Masubuchi, Y

POLYMER JOURNAL 2026年6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：Polymer Journal

This review describes the development and applications of multichain coarse-grained simulations for entangled polymer dynamics. The mean-field tube model has long served as the standard paradigm for describing the many-body entanglement problem as the motion of a single chain in a static field; it faces intrinsic limitations when spatial correlations, fluctuations, and complex topological rearrangements are addressed. To overcome these limitations, “multichain” approaches—specifically, the primitive chain network and multichain slip-spring models—were developed. These simulations explicitly resolve the force balance and topological coupling between multiple chains in three-dimensional space. This review covers the primitive chain network model, which emphasizes real-space force balance, and the multichain slip-spring model, which is derived from a well-defined free energy functional. Linear and nonlinear rheology predictions are discussed, along with molecular mechanisms such as constraint release and stretch/orientation-induced reductions in friction. Extensions to branched polymers, wall-slip phenomena, and network polymers are also mentioned.

DOI： 10.1038/s41428-026-01206-0

A toy model for the cycle rank dependence of stretch at break in phantom chain network simulations 招待有り査読有り国際誌 Open Access

Masubuchi, Y

JOURNAL OF NON-NEWTONIAN FLUID MECHANICS 349 巻 2026年6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：Journal of Non Newtonian Fluid Mechanics

The relationship between the topological architecture of polymer networks and their macroscopic rupture remains a fundamental challenge in polymer physics. Recent coarse-grained simulations have revealed that the dependence of stretch at break (λ<inf>b</inf>) on node functionality and reaction conversion can be unified into a universal master curve when plotted against the cycle rank density (ξ). However, a theoretical derivation explaining this universality has been lacking. This study proposes a simple mechanical model to describe the ξ-dependence of λ<inf>b</inf>. The polymer network is modeled as a mechanical system consisting of a sequence of springs representing localized, highly stretched strands and the surrounding unstretched network. By relating the stiffness contrast between these regions to the network connectivity defined by ξ, an analytical expression for the stretch at break is derived: λ<inf>b</inf>−1∝(3ξ+6)/(3ξ+2). The proposed model is validated against phantom chain simulations using both Gaussian and finite extensibility (FENE) springs. The theoretical prediction shows reasonable agreement with simulation data, providing a physical basis for the phenomenological universality observed in polymer network rupture.

DOI： 10.1016/j.jnnfm.2026.105620

Open Access

Web of Science

Scopus

Primitive chain network simulations of the creep of entangled polymers 招待有り査読有り国際共著 Open Access

Yuichi Masubuchi, Giovanni Ianniruberto, and Giuseppe Marrucci

Discover Polymers 3 巻頁： 3 2026年1月

The Hypoexponential Form for the Fiber-length Distribution in Thermoplastic Composites Revisited: Finite Initial Length, Cascade Fracture, and Its Mechanistic Status 招待有り査読有り国際誌 Open Access

Yuichi Masubuchi

Open Transport 2026年1月

Relation between Extensional Viscosity and Polymer Conformation in Dilute Polymer Solutions 査読有り国際誌 Open Access

KoIDE, Y; Ishida, T; Uneyama, T; Masubuchi, Y

NIHON REOROJI GAKKAISHI 54 巻 ( 2 ) 頁： 85 - 93 2026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：Nihon Reoroji Gakkaishi

We investigate extensional viscosity and polymer conformation in dilute polymer solutions under uniaxial extensional flow using dissipative particle dynamics simulations. At high extension rates, polymers are significantly stretched by extensional flows, and the extensional viscosity growth function exhibits strain hardening. To reveal their quantitative relation, we adopt an analysis method based on the Rouse-type model. We demonstrate that the extensional viscosity growth function is determined by the instantaneous gyration radii in the parallel and perpendicular directions to the extensional direction and their time derivatives. Our approach also provides a framework to describe the steady-state extensional viscosity of dilute polymer solutions for various chain lengths and concentrations in terms of the polymer gyration radius.

DOI： 10.1678/rheology.54.85

A Review on Molecular Simulations for the Rupture of Polymer Networks 招待有り査読有り Open Access

Yuichi Masubuchi, Takato Ishida, Yusuke Koide, and Takashi Uneyama

Science and Technology of Advanced Materials 26 巻 ( 1 ) 頁： 2587391 2025年12月

Influence of stretching boundary conditions on fracture in phantom star polymer networks: From volume to cross-sectional area conservation 招待有り査読有り国際誌 Open Access

Masubuchi, Y; Ishida, T; Koide, Y; Uneyama, T

POLYMER 340 巻頁： 129280 2025年12月

担当区分：筆頭著者,　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：Polymer

This study systematically investigates the effect of stretching boundary conditions—ranging from conservation of cross-sectional area to conservation of volume—on the rupture behavior of phantom star polymer networks using energy-minimizing coarse-grained molecular simulations. By continuously varying the deformation parameter, the simulations reveal that true stress and rupture characteristics, such as strain and stress at break and work for rupture, systematically decrease as the boundary condition approaches cross-sectional area conservation. In contrast, nominal stress and the corresponding rupture characteristics exhibit near-independence from boundary conditions, indicating that bond tension remains largely unaffected for phantom networks under the examined conditions. These results clarify that volume expansion primarily drives deviations in true stress and highlight a critical distinction between true and nominal stress-strain definitions. The difference between true and nominal stress-strain relations also affected the scaling exponent for strand length dependence on stretch at break. The findings stress the importance of specifying both deformation boundary conditions and stress-strain definitions in polymer network simulations for accurate interpretation of mechanical properties.

DOI： 10.1016/j.polymer.2025.129280

Steady-State Extensional Viscosity of Wormlike Micellar Solutions via Dissipative Particle Dynamics Simulations 査読有り国際誌 Open Access

Koide, Y; Ishida, T; Uneyama, T; Masubuchi, Y

MACROMOLECULES 58 巻 ( 22 ) 頁： 12039 - 12051 2025年11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

We investigate the steady-state extensional viscosity of wormlike micellar solutions using dissipative particle dynamics simulations. As the extension rate increases, the steady-state extensional viscosity initially increases and subsequently decreases after reaching a maximum, as observed in experiments. We reveal that this nonmonotonic behavior arises from the competition between micellar stretching and scission under uniaxial extensional flow. We further propose a relation that connects the extensional viscosity to micellar structures and kinetics. This relation provides a unified description of the extensional viscosity of unentangled wormlike micellar solutions for various temperatures, concentrations, and extension rates.

DOI： 10.1021/acs.macromol.5c01993

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

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

POLYMER DEGRADATION AND STABILITY 239 巻 2025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：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 (k<inf>2</inf>) 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 O<inf>2</inf> addition rate: (i) reaction kinetics, (ii) the degree of heterogeneity, and (iii) amount of crosslinking. Namely, reducing O<inf>2</inf> 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

Web of Science

Scopus

Primitive chain network simulations of double peaks in viscosity growth curves of densely branched pom-pom polymer melts in fast shear flows 査読有り国際共著国際誌

Masubuchi, Y; Schussmann, MG; Hyun, K; Wilhelm, M; Hirschberg, V; Ianniruberto, G; Marrucci, G

RHEOLOGICA ACTA 64 巻 ( 6-7 ) 頁： 263 - 271 2025年7月

担当区分：筆頭著者,　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：Rheologica Acta

Despite many attempts, the molecular mechanism of the nonlinear viscoelastic response of polymeric liquids in fast shear flows has not yet been fully elucidated. In this study, we examined the viscosity growth curves for a few well-characterized, nearly monodisperse, densely branched pom-pom polystyrene melts. The viscosity growth curves exhibit double peaks rather than the widely reported (for most polymer melts) single peak. To investigate the underlying molecular mechanism responsible for the observed behavior, we conducted primitive chain network (multi-chain sliplink) simulations, and found that the first and second peaks correspond to arm orientation and backbone stretch, respectively. We further observed that backbone stretch is reduced by coherent molecular tumbling at the flow start-up, and hence the second peak intensity comes out comparable to that of the orientation-induced first peak. In our sample, the number of backbone entanglements is small, so the mechanism of branchpoint withdrawal does not play a significant role.

DOI： 10.1007/s00397-025-01502-1

Web of Science

Scopus

Persistence Length and Plateau Modulus of Semiflexible Entangled Polymers in Primitive Chain Network Simulations 査読有り国際誌

Masubuchi Y., Tassieri M., Ianniruberto G., Marrucci G.

Nihon Reoroji Gakkaishi 53 巻 ( 3 ) 頁： 119 - 125 2025年6月

担当区分：筆頭著者,　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：Nihon Reoroji Gakkaishi

The relationship between the plateau modulus (G<inf>0</inf>) and the persistence length (L<inf>p</inf>) of entangled semiflexible polymers is still uncertain. Some previous theoretical models have predicted that G<inf>0</inf> decreases with increasing L<inf>p</inf>, while experiments indicated the opposite. In this study, we extend the primitive chain network (PCN) model to incorporate bending rigidity at the scale of the entanglement length, consistently with the coarse graining of the model. Simulations investigate the effects of rigidity (and of molecular weight) on chain conformation and relaxation modulus. Our results reveal a relationship described as G<inf>0</inf> ~ L<inf>p</inf>2/3, indicating that G<inf>0</inf> increases with increasing L<inf>p</inf>, consistently with experiments. It should be considered, however, that implicit in our simulations is the condition that the entanglement length is kept fixed with changing L<inf>p</inf>

DOI： 10.1678/rheology.53.119

Scopus

CiNii Research

Phantom Chain Simulations for the Fracture of Star Polymer Networks on the Effect of Arm Molecular Weight 査読有り国際誌

Masubuchi, Y

MACROMOLECULES 58 巻 ( 12 ) 頁： 6399 - 6405 2025年6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：Macromolecules

This study investigated the fracture of star polymer networks made from pre-polymers with various arm molecular weights in the range, 2 ≤ N<inf>a</inf> ≤ 20, for node functionalities 3 ≤ f ≤ 8 and conversion ratios 0.6 ≤ φ<inf>c</inf> ≤ 0.95 by phantom chain simulations. The networks were created via end-linking reactions of star polymers dispersed in a simulation box with a fixed monomer density ρ = 8. The resultant networks were alternatively subjected to energy minimization and uniaxial stretch until the break. The stretch at the break, λ<inf>b</inf>, depended on the strand molecular weight N<inf>s</inf> = 2N<inf>a</inf> + 1 with a power-law manner described as λ<inf>b</inf> ∼ N<inf>s</inf>0.67, consistent with the experiment. However, the strand length before stretch is proportional to N<inf>s</inf>0.5, which does not explain the observed N<inf>s</inf>-dependence of λ<inf>b</inf>. The analysis based on the non-affine deformation theory does not interpret the phenomenon either. Instead, the increase of normalized pre-polymer concentration concerning the overlapping concentration with increasing N<inf>s</inf> explains the result through a rise in the fraction of broken strands.

DOI： 10.1021/acs.macromol.5c00475

Web of Science

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

JOURNAL OF CHEMICAL PHYSICS 162 巻 ( 17 ) 2025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：Journal of Chemical Physics

We investigate the concentration dependence of surfactant diffusion in wormlike micellar solutions using dissipative particle dynamics simulations. The simulations show that the self-diffusion coefficient of surfactants exhibits a nonmonotonic dependence on the surfactant concentration, as observed in previous experiments. We quantitatively reveal that this nonmonotonic behavior results from the competition between micellar center-of-mass diffusion and surfactant diffusion within micelles by decomposing the mean-square displacement of surfactants into the corresponding contributions. Furthermore, our detailed analyses demonstrate how the competition between the two diffusion mechanisms is governed by the aggregation number distribution, the dynamics of individual surfactants and micelles, and the kinetics of micellar scission and recombination.

DOI： 10.1063/5.0266470

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

JOURNAL OF CHEMICAL PHYSICS 162 巻 ( 5 ) 2025年2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：Journal of Chemical Physics

Reverse nonequilibrium molecular dynamics (RNEMD) simulations impose a flux by swapping the velocities of two particles. This method allows for the calculation of transport coefficients, such as thermal conductivity and viscosity. The relation between the induced fluxes and the control parameters of RNEMD (such as the time interval between successive swap events) is not clear. Thus, trial-and-error is required to realize the desired fluxes in RNEMD simulations. In this study, we develop a theoretical framework using extreme value statistics to estimate the relation between the time interval and the resulting induced fluxes. Our RNEMD simulations, conducted with varying time intervals, confirm that the theoretical predictions are quantitatively consistent with the simulation results when the time interval exceeds the momentum relaxation time. Our RNEMD simulations also show that our theoretical predictions, which are valid for a large number of particles for swap candidates, work well even for a relatively small number of particles for swap candidates. These findings demonstrate that the induced fluxes can be reliably estimated, providing a valuable tool for selecting appropriate RNEMD parameters for simulations.

DOI： 10.1063/5.0236799

Direct Observation of the Compression Behavior of Polystyrene Microbeads in a Diamond Anvil Cell 査読有り国際誌 Open Access

Moriguchi, H; Niwa, K; Hasegawa, M; Koide, Y; Ishida, T; Uneyama, T; Masubuchi, Y

NIHON REOROJI GAKKAISHI 53 巻 ( 5 ) 頁： 209 - 213 2025年

Brownian simulations for fracture of star polymer phantom networks 招待有り査読有り国際誌

Masubuchi, Y; Koide, Y; Ishida, T; Uneyama, T

POLYMER JOURNAL 2024年11月

担当区分：筆頭著者,　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：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

Web of Science

Scopus

researchmap

　前のページ - 次のページ　

<増渕 雄一>

論文 - 増渕 雄一

<増渕　雄一>

論文 - 増渕　雄一