論文 - 荒井　規允

Effect of Propylene-Oxide Segment Length on Cleansing Performance of Detergents With Nonionic Surfactants

Osato, N; Joko, A; Ikeda, H; Arai, N

JOURNAL OF SURFACTANTS AND DETERGENTS 2025年07月

ISSN  1097-3958

　概要を見る

Understanding the relationship between surfactant molecular structure and cleansing performance is essential for the rational design of high-performance detergents. In this study, we investigate the effect of propylene oxide (PO) chain length on the detergency of nonionic surfactants through a combination of experimental measurements and coarse-grained molecular simulations. Experimentally, detergency tests revealed that increasing the PO content leads to a systematic decrease in cleansing performance. Dissipative particle dynamics simulations were performed to elucidate the molecular basis of this behavior. In bulk aqueous solutions, all surfactants self-assembled into micelles, with longer PO chains resulting in slightly larger and more diffuse micellar structures. At a model dirt surface, surfactants with longer PO chains exhibited stronger adsorption and slower desorption under flow conditions compared to surfactants without PO units. These findings suggest that while PO segments enhance interfacial adsorption, excessive retention at the surface can hinder soil removal, thereby reducing overall detergency. This combined experimental and simulation approach provides molecular-level insights into designing optimized nonionic surfactants for practical cleansing applications.

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Molecular insights into the motion of oil droplets in aqueous solutions of ester- and amide-containing cationic surfactants

Ueno K., Ishiwatari Y., Sasaki K., Kojima T., Takai A., Asakura K., Arai N., Banno T.

Journal of Molecular Liquids 426 2025年05月

ISSN  01677322

　概要を見る

The study of self-propelled motion in soft matter systems has garnered significant interest owing to its potential applications in microfluidics, soft robotics, and autonomous system design. Understanding the molecular mechanisms underlying motility is crucial for advancing these applications. This study investigates the self-propelled motion of lauronitrile oil droplets in aqueous surfactant solutions, focusing on the impact of different surfactant molecular structures on droplet dynamics. This study compares surfactants with ester and amide linkages, highlighting their critical role in modulating interfacial tension and driving Marangoni convection, a key factor behind droplet movement. Surfactants with ester linkages exhibit a high affinity for lauronitrile and rapidly adsorb at the oil–water interface, generating strong Marangoni flows and driving fast droplet motion. In contrast, amide-containing surfactants exhibit slower adsorption and weaker interactions with lauronitrile, leading to reduced or absent motion. These findings provide new insights into the molecular mechanisms underlying the self-propelled droplet behavior in non-equilibrium systems and contribute to a deeper understanding of self-organizing phenomena.

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Investigating the Nanostructure Design Mechanism Behind the Hydrophobicity of the Biomimetic Surface

Meng, F; Liu, JL; Arai, N

ACS APPLIED MATERIALS & INTERFACES 17 （ 15 ） 23394 - 23404 2025年04月

ISSN  1944-8244

　概要を見る

Wettability, a fundamental physicochemical property of functional materials that depends on their surface structure, has seen recent advances in understanding that have led to the development of superhydrophobic surfaces with applications in self-cleaning materials and antifogging coatings. Given the presence of a free energy barrier between the Cassie and Wenzel states, calculating this barrier provides a valuable means to assess surface hydrophobicity. We hypothesize that surface characteristics affect the free energy barrier between wetting states and that the determination of this barrier can be used to predict the hydrophobicity. Focused on models of a butterfly wing (striped surface) and a mosquito eye (pillared surface), this study employed many-body dissipative particle dynamics (mDPD) simulations to explore the relationship between the free energy barrier and surface roughness (height and spacing). For small-radius droplets, the height of the surface pattern predominantly influences the hydrophobicity. Conversely, for large-radius droplets, the spacing of the surface pattern is the dominant factor. Considering that the contact angle indicates static hydrophobicity, the free energy barrier is the indicator of dynamic hydrophobicity, which shows how well the surface can maintain its hydrophobicity under the impact of a droplet. This study underscores the advantages of the free energy barrier method in understanding dynamic hydrophobicity, which can be applied in evaluating high kinetic energy droplets onto surfaces, for example, automobiles, trains, and aircraft.

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Synthesis of Amorphous Graphene and Graphene Oxide Analogues

Sakuma, T; Sato, R; Yamaguchi, A; Imai, H; Arai, N; Oaki, Y

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 147 （ 13 ） 11564 - 11573 2025年04月

ISSN  0002-7863

　概要を見る

Graphene and graphene oxide (GO) are promising two-dimensional nanomaterials. An ultimate goal is to achieve large-scale bottom-up syntheses of perfect graphene and GO. However, controlled syntheses of perfect graphitic structures still remain challenges in chemistry and materials science. Moreover, amorphous types have not received much attention. The present work shows syntheses, structures, and applications of amorphous graphene and GO analogues alternative to the ideal ones. The simultaneous multiple reactions of two conjugated monomers provide amorphous conjugated polymer networks containing low-crystalline graphitic domains and their stacking. The stacked amorphous graphene and GO are exfoliated into thin nanosheets including few-layers and monolayers. Moreover, in situ syntheses of the amorphous GO analogues are applied to obtain a reinforced plastic with high mechanical strength. The present work implies that various functional nanocarbons can be designed and synthesized by tailored combinations of conjugated monomers.

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Effects of grafting architecture of amphiphilic polymer-grafted nanoparticles on stabilization mechanisms of concentrated emulsions

Suzuki, K; Kobayashi, Y; Yamazaki, T; Tsuji, T; Arai, N

COLLOID AND INTERFACE SCIENCE COMMUNICATIONS 65 2025年03月

ISSN  2215-0382

　概要を見る

This study explores the stabilization mechanisms of concentrated emulsions with tunable morphology using amphiphilic polymer-grafted nanoparticles (PGNPs). We employ coarse-grained molecular simulations to investigate concentrated oil-in-water emulsions stabilized by partially hydrolyzed poly(vinyl alcohol)-grafted poly(methyl methacrylate) (PMMA) particles. Two grafting architectures were examined: hydrophilic-hydrophobic (AB-type) diblock PGNPs and reverse BA-type diblock PGNPs. Our findings reveal that AB-type diblock PGNPs tend to aggregate, leading to droplet-droplet coalescence. In contrast, BA-type diblock PGNPs disperse effectively in the water phase, stabilizing robust emulsion through a space-filling mechanism. The study further demonstrates that the stability and morphology of the emulsions can be tuned by varying the number of PGNPs. Our results suggest that BA-type diblock PGNPs are more effective in stabilizing concentrated emulsions, offering insights for the design of novel emulsifiers in industrial applications.

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Fundamentals of Toughening Core-Shell Bioplastic Materials from a Molecular Perspective

Yamaguchi, A; Arai, S; Arai, N

ACS SUSTAINABLE CHEMISTRY & ENGINEERING 13 （ 1 ） 535 - 546 2025年01月

ISSN  2168-0485

　概要を見る

This study analyzed the fracture behavior of poly(lactic acid) (PLA)/polybutylene succinate (PBS)/thermoplastic starch (TPS) blends featuring nanoscale-dispersed core-shell structures using molecular dynamics (MD) simulations, elucidating the toughening mechanisms at the molecular-level. Four models (PLA/TPS25, PLA/PBS/TPS5, PLA/PBS/TPS25, and PLA/PBS/TPS50) with varying core-shell structure parameters were utilized in the MD simulations. The fracture energy relationship obtained from the deformation simulation was PLA/PBS/TPS25 > PLA/PBS/TPS5 > PLA/PBS/TPS50 ≈ PLA/TPS25, which generally reproduced the experimental results of the impact test of the blends. The entire material was fractured by delamination at the TPS/PLA interface in the PLA/TPS25, and at the TPS/PBS interface in the PLA/PBS/TPS50 with the thinnest PBS shell. The PLA/PBS/TPS5 with the thickest PBS shell exhibited a reduced toughening effect due to the formation of numerous voids in the PLA matrix phase during deformation. In PLA/PBS/TPS25 with an intermediate thickness PBS shell, moderate-density voids formed during deformation, releasing strain constraints and effectively strengthening the material. The orientation hardening of PLA and PBS that occurs during deformation also contributes to the deformation energy absorption of PLA/PBS/TPS25. The molecular-level toughening mechanism elucidated in this study is anticipated to contribute to the enhancement of the properties of a wide range of bioplastics containing polysaccharides.

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分子シミュレーションと機械学習を活用した界面活性剤水溶液の構造・物性予測

荒井 規允

オレオサイエンス （公益社団法人 日本油化学会）  25 （ 7 ） 285 - 289 2025年

ISSN  13458949

　概要を見る

<p>界面活性剤はソフトマターの一種として，分子設計の自由度が高く，自己集合構造や物性に多様性を示す。しかし，それゆえ材料内部の挙動は複雑であり，その潜在能力を十分に引き出すのは容易ではない。本研究では，界面活性剤水溶液の構造と機能を予測するために，分子シミュレーションと機械学習を活用した研究例を紹介する。まず，散逸粒子動力学法を用いて200種以上のクレンジング剤処方に対する自己集合構造を再現・解析した。次に，分子記述子を特徴量とした機械学習モデルを構築し，高精度な洗浄性能予測を実現した。さらに，分子の化学構造から自己集合構造を予測する深層学習モデルを構築し，機能性界面活性剤の効率的な設計手法としての有効性を示した。</p>

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A molecular strategy for creating functional vesicles with balancing structural stability and stimuli-responsiveness

Sasaki, S; Ueno, H; Arai, N; Asakura, K; Banno, T

NANOSCALE 17 （ 11 ） 6863 - 6873 2025年

ISSN  2040-3364

　概要を見る

Vesicles, closed bilayer structures composed of amphiphiles, have attracted considerable attention as functional materials. Structural stability and stimulus responsiveness are required for next-generation functional vesicles. However, there is a dilemma between these properties because the desired membrane structure varies in terms of structural stability and stimulus sensitivity. Herein, we propose a new approach for the development of giant vesicles (GVs) through the molecular design and synthesis of amphiphiles with or without amide linkages, forming hydrogen bonding. From the ¹H NMR analysis and fluorescence spectra of environment-responsive probes, intermolecular hydrogen bonding between the amide linkages in the membrane contributed to the enhanced structural stability of the GVs. Moreover, by adding amphiphiles containing a photoresponsive azobenzene moiety to GVs composed of amphiphiles with or without amide linkages, a distinct mechanism of photoresponsive deformation was observed: the former exhibited large and irreversible deformation, while the latter showed a modest and reversible manner due to the photoisomerisation of azobenzene under ultraviolet and subsequent visible light illumination. This difference was also attributed to the membrane structure affected by intermolecular hydrogen bonding. Based on these results, the finding provides a molecular methodology for developing highly functional vesicles.

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Molecular modelling of active oil droplet propulsion: Insights from dissipative particle dynamics simulation

Sasaki, K; Ishiwatari, Y; Ueno, K; Kojima, T; Banno, T; Arai, N

CHEMICAL PHYSICS LETTERS 857 2024年12月

研究論文（学術雑誌）, 最終著者, 査読有り,  ISSN  0009-2614

　概要を見る

This study employed dissipative particle dynamics (DPD) simulations to investigate the self-propelled motion of oil droplets in water–oil–surfactant systems. It is the first attempt to replicate self-propulsion models of oil droplets at the molecular level, contrasting previous simulations focused on Brownian motion and hydrodynamic behaviour of colloidal particles. The DPD model reproduced droplet propulsion and visualised internal Marangoni flow, showing that larger droplet radii and greater interfacial tension differences increase propulsion speeds. Additionally, surfactants with stronger oil–oil repulsion enhanced propulsion speed, suggesting that surfactant-induced local structures are crucial for the self-propulsion mechanism.

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Poly(vinyl alcohol)-modified poly(methyl methacrylate) particles for solid-stabilized oil-in-water emulsions (vol 697, 134433, 2024)

Yamazaki, T; Suzuki, K; Kobayashi, Y; Arai, N; Tsuji, T

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS （Elsevier BV）  704   135683 - 135683 2024年11月

研究論文（学術雑誌）, 査読有り,  ISSN  0927-7757

　概要を見る

The authors regret to inform you that we have discovered a mistake in our original modeling of poly(methyl methacrylate) (PMMA) shown in Fig. 1(b) in Ref. [1]. We reran all-atomistic molecular dynamics (MD) simulations with the corrected molecular structure of PMMA (Fig. 1(b)) to obtain interaction parameters, a<inf>ij</inf>, and have revised a<inf>ij</inf> as shown in Table 1. In addition, the dissipative particle dynamics (DPD) simulations of the biphasic system with this corrected a<inf>ij</inf> were performed to see the behavior of poly(vinyl alcohol) (PVA) adsorbed onto the PMMA surface. We found no deviations from Fig. 10 and Fig. 11 in Ref. [1]. Therefore, the conclusion of the article [1] is unaffected. The authors would like to apologize for any inconvenience caused.

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Poly(vinyl alcohol)-modified poly(methyl methacrylate) particles for solid-stabilized oil-in-water emulsions

Yamazaki, T; Suzuki, K; Kobayashi, Y; Arai, N; Tsuji, T

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS （Elsevier BV）  697   134433 - 134433 2024年09月

研究論文（学術雑誌）, 査読有り,  ISSN  0927-7757

　概要を見る

In this study, submicron poly(methyl methacrylate) (PMMA) particles with surfaces modified using poly(vinyl alcohol) (PVA) (PMMA-PVA) were produced to formulate solid-stabilized oil-in-water (O/W) emulsions including high internal phase emulsions with a dispersed phase of over 74 %. The high-internal phase emulsions stabilized by PMMA–PVA exhibited gel-like behavior, and the oil droplets exhibited faceted shapes. PVA with a degree of saponification of 80 and 88 mol% was used as the surface modifier rather than PVA with > 96 mol%, assisting in the formation of a robust adsorbed layer on the PMMA particles. Coarse-grained molecular simulations revealed that the partially-hydrolyzed PVA exhibited a better adsorption behavior compared to the fully-hydrolyzed PVA, being thermodynamically adsorbed onto the PMMA surface in water owing to stable adsorption via its hydrophobic acetyl groups. Furthermore, PMMA–PVA reduced the interfacial tension as the degree of saponification of PVA decreased. Simulation and experimental results suggested that the acetyl groups of PVA not only adsorbed onto the PMMA surface but also promoted adsorption between PMMA and the oil–water interface. Overall, the findings of this study underscore the potency of PMMA–PVA as a particulate stabilizer for formulating O/W high internal phase emulsions.

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Coarse-grained molecular simulation of the effect of liquid crystal molecular pitch on structure in cylindrical confinement

Sato, T; Tsujinoue, H; Arai, N; Takahashi, KZ

PHYSICAL REVIEW E 110 （ 1 ） 014701 2024年07月

研究論文（学術雑誌）, 査読有り,  ISSN  2470-0045

　概要を見る

Blue phases (BPs) consist of three-dimensional self-assembled structures formed by a double-twisted columnar arrangement of liquid crystal molecules. Although their unique optical and structural properties render BPs particularly useful for applications such as liquid crystal displays, BPs typically appear in a narrow temperature range between the isotropic and nematic phases. This thermodynamic instability impedes their practical applicability. However, the simulations we present here showed that, in a quasi-one-dimensional system confined to nanospace, a phase equivalent to the BP appears and persists between the nematic and smectic phases. Confinement to a nanotube (NT) with a relatively small radius enables the BP to be maintained over a wide temperature range, whereas for an NT with a relatively larger radius, the BP appears only in a very narrow temperature range between the aforementioned phases. We additionally showed that the pitch of the BP is dependent on and can be controlled by adjusting the radius of the NTs. This finding has significant implications for the potential application of these materials in fields such as photonics and chiral separation technologies.

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Design strategy for blends of biodegradable polyester and thermoplastic starch based on a molecular dynamics study of the phase-separated interface

Yamaguchi, A; Arai, S; Arai, N

CARBOHYDRATE POLYMERS （Carbohydrate Polymers）  333   122005 2024年06月

研究論文（学術雑誌）, 最終著者, 査読有り,  ISSN  0144-8617

　概要を見る

Molecular insight into the phase-separated interface formed when biodegradable polyesters and thermoplastic starch (TPS) are melt-blended is valuable for the design of composites. In this study, eight different interfaces combining four major biodegradable polyesters (PLA, PBS, PHB and PBAT) and two TPSs [unmodified TPS (nTPS) and citrate-modified TPS (cTPS)] were investigated by using molecular dynamics (MD) simulations. According to the MD simulation results, PBS, PHB and PBAT diffuse readily into the TPS and form compatible interfaces, whereas PLA is less compatible with the TPS. The results of tensile simulations show that PBS and PBAT adhere well to TPS; in particular, PBS/cTPS and PBAT/cTPS exhibit high interfacial-fracture energy (G). Both PLA and PHB blended with TPS exhibit low G because PLA is less compatible with TPS and PHB and TPS have low electrostatic interaction. The reason for the high G of PBS/cTPS and PBAT/cTPS is thought to be a combination of three factors: (i) formation of a deep compatible interface, (ii) suppression of void growth by electrostatic interactions and (iii) absorption of strain energy by a change in the conformation of the molecular chains. These three interfacial adhesion mechanisms should be considered when designing biodegradable polyester/TPS blends with good mechanical properties.

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In-layer inhomogeneity of molecular dynamics in quasi-liquid layers of ice.

Yasuda I, Endo K, Arai N, Yasuoka K

Communications chemistry 7 （ 1 ） 117 2024年05月

研究論文（学術雑誌）, 査読有り,  ISSN  2399-3669

　概要を見る

Quasi-liquid layers (QLLs) are present on the surface of ice and play a significant role in its distinctive chemical and physical properties. These layers exhibit considerable heterogeneity across different scales ranging from nanometers to millimeters. Although the formation of partially ice-like structures has been proposed, the molecular-level understanding of this heterogeneity remains unclear. Here, we examined the heterogeneity of molecular dynamics on QLLs based on molecular dynamics simulations and machine learning analysis of the simulation data. We demonstrated that the molecular dynamics of QLLs do not comprise a mixture of solid- and liquid water molecules. Rather, molecules having similar behaviors form dynamical domains that are associated with the dynamical heterogeneity of supercooled water. Nonetheless, molecules in the domains frequently switch their dynamical state. Furthermore, while there is no observable characteristic domain size, the long-range ordering strongly depends on the temperature and crystal face. Instead of a mixture of static solid- and liquid-like regions, our results indicate the presence of heterogeneous molecular dynamics in QLLs, which offers molecular-level insights into the surface properties of ice.

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Cholesteric liquid crystal phase variations within nanotubes: an in-depth analysis of the influences of twist radius and molecular pitch

Yamada, K; Arai, N

LIQUID CRYSTALS （Liquid Crystals）  51 （ 7 ） 1204 - 1214 2024年05月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り,  ISSN  0267-8292

　概要を見る

This study investigates the self-assembly and phase transitions of cholesteric liquid crystals (CLCs) when confined in nanotubes, specifically focusing on the variations in their molecular structures. A dissipative particle dynamics method was used to investigate how the changes in helix radius ((Formula presented.)) and pitch ((Formula presented.)) affect the behaviour of the LCs. For pitches of 24, 12, and 6, the orientation order parameter ((Formula presented.)) showed distinct trends during cooling. Smaller helix radii resulted in isotropic to nematic to smectic phase transitions, whereas larger radii resulted in a novel smectic phase with spiral structures (Sm (Formula presented.)). Circumferential local-order parameters ((Formula presented.) and (Formula presented.)) were introduced to better characterise the phases, and a disordered spiral-structure phase (Sm (Formula presented.)) with local perturbations was observed. The transitions between isotropic, nematic, and smectic phases, highlighting the influence of the pitch and helix radius, were observed from the phase diagrams. Smaller pitches and radii prevented the formation of stable structures; however, specific combinations induced characteristic spiral structures in the smectic phase. These results provide new insights into the self-assembly of confined CLCs, which have potential applications in the design of photonic devices and LC-based sensors. This study advances our understanding of phase control in quasi-one-dimensional systems and highlights the importance of molecular variations in liquid crystal behaviour.

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Supramolecular copolymerization of hydrophobic and hydrophilic monomers in liquid crystalline media

Morishita, D; Itoh, Y; Furukawa, K; Arai, N; Zhang, XJ; Aida, T

CHEMICAL SCIENCE （Chemical Science）  15 （ 11 ） 4068 - 4074 2024年

研究論文（学術雑誌）, 査読有り,  ISSN  2041-6520

　概要を見る

In the case of covalent polymers, immiscible polymers can be integrated by covalently linking them together, but such a strategy is not possible in supramolecular polymers. Here we report the supramolecular copolymerization of two porphyrin-based monomers, C10P2H and TEGPCu with side chains bearing cyanobiphenyl (CB) groups at the ends of hydrophobic alkyl or hydrophilic tetraethylene glycol chains, respectively. These monomers undergo self-sorting supramolecular polymerization in highly diluted solutions ([monomer] = 3.4 × 10−9 mol% (2.0 × 10−8 mol L−1)) in nonpolar media due to the incompatibility of the side chains. Surprisingly, these monomers undergo supramolecular copolymerization under high concentration conditions ([monomer] = 7.7 mol%) in the medium of 4-cyano-4′-pentyloxybiphenyl (5OCB) to form a columnar liquid crystalline phase under thermodynamic conditions, where the individual columns are composed of supramolecular block copolymers. The combination of CB ends of both monomers and the 5OCB medium is essential for the two monomers to form an integrated structure in a condensed system without phase separation.

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Machine learning prediction of self-assembly and analysis of molecular structure dependence on the critical packing parameter

Ishiwatari, Y; Yokoyama, T; Kojima, T; Banno, T; Arai, N

MOLECULAR SYSTEMS DESIGN & ENGINEERING （Molecular Systems Design and Engineering）  9 （ 1 ） 20 - 28 2024年

研究論文（学術雑誌）, 査読有り,  ISSN  2058-9689

　概要を見る

Amphiphilic molecules spontaneously form self-assembly structures depending on physical conditions such as the molecular structure, concentration, and temperature. These structures exhibit various functionalities according to their morphology. The critical packing parameter (CPP) is used to correlate self-organized structures with the chemical composition. However, accurately calculating it requires information about both the molecular shape and molecular aggregates, making it challenging to apply directly in molecular design. We aimed to predict the self-assembled structure of a molecule directly from its chemical structure and to analyze the factors influencing it using machine learning. Dissipative particle dynamics simulations were used to reproduce many self-assembly structures comprising various chemical structures, and their CPPs were calculated. Machine learning models were built using the chemical structures as input data and the CPPs as output data. As a result, both random forest and the gated recurrent unit showed high prediction accuracy. Feature importance analysis and sample size dependence revealed that the amphiphilic nature of molecules significantly influences the self-assembly structures. Additionally, selecting an appropriate molecular structure representation for each algorithm is crucial. The study results should contribute to product development in the fields of materials science, materials chemistry, and medical materials.

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Mechanisms underlying the stability and instability of concentrated oil-in-water emulsions: Effect of the chemical structure of amphiphilic polymers

Suzuki, K; Kobayashi, Y; Yamazaki, T; Tsuji, T; Arai, N

JOURNAL OF MOLECULAR LIQUIDS （Journal of Molecular Liquids）  394   123749 - 123749 2023年12月

研究論文（学術雑誌）, 査読有り,  ISSN  0167-7322

　概要を見る

Despite extensive experimentation to efficiently prepare concentrated oil-in-water (O/W) emulsions with sufficient stability, the effect of the chemical structure of the polymeric surfactants on the emulsion stability is not yet understood in detail at the molecular level. We investigated the effect of the degree of saponification and arrangement of the hydrophobic (acetyl) groups of poly(vinyl alcohol) (PVA) on the stability of the concentrated emulsion via a combination of experiments and coarse-grained molecular simulations. This was accomplished by varying the degree of saponification and the arrangement of the hydrophobic groups on PVA, and by systematically changing the volume fraction of PVA molecules. The stability of the emulsion was adversely affected by the presence of an excess or the complete absence of hydrophobic groups on PVA. The former situation promotes the aggregation of PVA molecules with each other; conversely, fully saponified PVA molecules penetrate the water phase, thereby decreasing the number of PVA molecules at the O/W interface. Thus, the depletion of the interface of PVA molecules increases the interfacial tension, and, consequently, destabilizes the interface. Adjustment of the degree of saponification to a suitable value (80%) led to the formation of stable, concentrated emulsions with a smaller amount of PVA. For PVA with an appropriate degree of saponification, the interfacial behavior of concentrated O/W emulsions was to a lesser extent affected by the arrangement of the hydrophobic groups of PVA compared to the degree of saponification. Furthermore, the individual PVA chains at the interface had planar conformations, regardless of the arrangement of the hydrophobic groups. Our results indicate that careful tuning of the degree of saponification, rather than the arrangement of the hydrophobic groups of PVA, is necessary to control the interfacial stability of concentrated O/W emulsions using PVA. The findings of this study provide support for departing from empirical trial-and-error approaches and may facilitate the development of emulsifiers with enhanced performance.

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Predicting the Performance of Functional Materials Composed of Polymeric Multicomponent Systems Using Artificial Intelligence—Formulations of Cleansing Foams as an Example

Masugu Hamaguchi, Hideki Miwake, Ryoichi Nakatake, Noriyoshi Arai

Polymers 2023年10月

研究論文（学術雑誌）, 査読有り

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The Relationship between Nanostructured Bio-Inspired Material Surfaces and the Free Energy Barrier Using Coarse-Grained Molecular Dynamics

Meng, F; Arai, N

BIOMIMETICS （Biomimetics）  8 （ 6 ）  2023年09月

研究論文（学術雑誌）, 査読有り

　概要を見る

Bio-inspired (biomimetic) materials, which are inspired by living organisms, offer exciting opportunities for the development of advanced functionalities. Among them, bio-inspired superhydrophobic surfaces have attracted considerable interest due to their potential applications in self-cleaning surfaces and reducing fluid resistance. Although the mechanism of superhydrophobicity is understood to be the free energy barrier between the Cassie and Wenzel states, the solid-surface technology to control the free energy barrier is still unclear. Therefore, previous studies have fabricated solid surfaces with desired properties through trial and error by measuring contact angles. In contrast, our study directly evaluates the free energy barrier using molecular simulations and attempts to relate it to solid-surface parameters. Through a series of simulations, we explore the behavior of water droplets on surfaces with varying values of surface pillar spacing and surface pillar height. The results show that the free energy barrier increases significantly as the pillar spacing decreases and/or as the pillar height increases. Our study goes beyond traditional approaches by exploring the relationship between free energy barriers, surface parameters, and hydrophobicity, providing a more direct and quantified method to evaluate surface hydrophobicity. This knowledge contributes significantly to material design by providing valuable insights into the relationship between surface parameters, free energy barriers, and hydrophilicity/hydrophobicity.

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