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柴田 基樹*; 中西 洋平*; 阿部 淳*; 有馬 寛*; 岩瀬 裕希*; 柴山 充弘*; 元川 竜平; 熊田 高之; 高田 慎一; 山本 勝宏*; et al.
Polymer Journal, 55(11), p.1165 - 1170, 2023/11
被引用回数：1 パーセンタイル：44.82(Polymer Science)Marine ecosystem degradation due to micro plastics is a significant environmental problem, as acknowledged by Sustainable Development Goal 14. Decomposition of plastics using near critical or supercritical water is one of the promising methods to reduce micro plastics. To attain the optimization of the method for improving environmental friendliness, it is necessary to clarify the structural change of materials during the process. We, thus, investigated the decomposition processes of polystyrene particles dispersed in deuterated water (D
O) during heating under near critical or supercritical conditions by using in situ small-angle neutron scattering. Under subcritical conditions, the PS particles were swollen by DO due to increased compatibility with temperature. Near the critical point in subcritical conditions, the cleavage of PS chains in the particles occurred, so that the swollen ratio was much enhanced though the PS particles kept their shapes. In a supercritical condition, the PS particles were degraded into oil including oligomers or monomers and the phase-separated structures with styrene-rich and DO-rich regions.
下北 啓輔*; 山本 勝宏*; 宮田 登*; 中西 洋平*; 柴田 基樹*; 竹中 幹人*; 山田 悟史*; 瀬戸 秀樹*; 青木 裕之; 宮崎 司*
Soft Matter, 19(11), p.2082 - 2089, 2023/03
被引用回数：0 パーセンタイル：0(Chemistry, Physical)In the case of poly(methyl methacrylate) (PMMA) thin films on a Si substrate, thermal annealing induces the formation of a layer of PMMA chains tightly adsorbed near the substrate interface, and the strongly adsorbed PMMA remains on the substrate, even after washing with toluene (hereinafter called adsorbed sample). Neutron reflectometry revealed that the concerned structure consists of three layers: an inner layer (tightly bound on the substrate), a middle layer (bulk-like), and an outer layer (surface) in the adsorbed sample. When an adsorbed sample was exposed to toluene vapor, it became clear that, between the solid adsorption layer (which does not swell) and bulk-like swollen layer, there was a "buffer layer" that could sorb more toluene molecules than the bulk-like layer. This buffer layer was found not only in the adsorbed sample but also in the standard spin-cast PMMA thin films on the substrate. When the polymer chains were firmly adsorbed and immobilized on the Si substrate, the freedom of the possible structure right next to the tightly bound layer was reduced, which restricted the relaxation of the conformation of the polymer chain strongly. The "buffer layer" was manifested by the sorption of toluene with different scattering length density contrasts.
下北 啓輔*; 山本 勝宏*; 宮田 登*; 有馬 寛*; 中西 洋平*; 竹中 幹人*; 柴田 基樹*; 山田 悟史*; 瀬戸 秀樹*; 青木 裕之; et al.
Langmuir, 38(41), p.12457 - 12465, 2022/10
被引用回数：0 パーセンタイル：0(Chemistry, Multidisciplinary)We measured the neutron reflectivity (NR) of isotactic polypropylene (PP) thin films deposited on Si substrates modified by hexamethyldisilazane (HMDS) at the saturated vapor pressure of deuterated water at 25
C and 60C/85% RH to investigate the effect of HMDS on the interfacial water accumulation in PP-based polymer/inorganic filler nanocomposites and metal/resin bonding materials. We found that the amount of water accumulated at the PP/Si interface decreased with increasing immersion time of the Si substrate in a solution of HMDS in hexane prior to PP film deposition. During the immersion of the Si substrate, the HMDS molecules were deposited on the Si substrate as a monolayer without aggregation. Furthermore, the coverage of the HMDS monolayer on the Si substrate increased with increasing immersion time. At 60C and 85% RH, only a slight amount of interfacial water was detected after HMDS treatment for 1200 min. As a result, the maximum concentration of interfacial water was reduced to 0.1 from 0.3, where the latter corresponds to the PP film deposited on the untreated substrate.
宮崎 司*; 下北 啓輔*; 山本 勝宏*; 青木 裕之; 山田 悟史*; 宮田 登*
Langmuir, 36(49), p.15181 - 15188, 2020/12
被引用回数：6 パーセンタイル：31.01(Chemistry, Multidisciplinary)We investigated the polymer chain dynamics in a 2-3 nm thick poly(vinyl acetate) (PVAc) adsorption layer on a Si substrate with a native oxide layer via neutron reflectometry combined with toluene vapor-induced swelling. We can investigate the polymer chain dynamics difference in the film thickness direction by the difference in the degree of swelling of the polymer layers detected by neutron reflectometry. The mobility of the polymer chains depends on the distance from the substrate. The results elucidated that the interfacial layer with a thickness of approximately 1 nm did not swell at all with toluene vapor, which is a solvent for PVAc. Meanwhile, the surface layer excessively swells with toluene vapor compared to the bulk. This indicates that the polymer chain within the interfacial region is immobilized by the substrate through hydrogen-bonding interaction, but in the surface region, the surface effect overcomes this interfacial interaction. We concluded that the polymer chains in the adsorption layer are either strongly constrained to the substrate, owing to hydrogen bonding, or more mobile than the bulk, owing to the surface effect.
宮崎 司*; 宮田 登*; 吉田 鉄生*; 有馬 寛*; 津村 佳弘*; 鳥飼 直也*; 青木 裕之; 山本 勝宏*; 金谷 利治*; 川口 大輔*; et al.
Langmuir, 36(13), p.3415 - 3424, 2020/04
被引用回数：14 パーセンタイル：60.48(Chemistry, Multidisciplinary)We investigated in detail the structures in the poly(vinyl alcohol) (PVA) adsorption layers on a Si substrate, which remained on the substrate after immersing the relatively thick 30 - 50 nm films in hot water, by neutron reflectometry under humid conditions. For the PVA with a degree of saponification exceeding 98 mol %, the adsorption layer exhibits a three-layered structure in the thickness direction. The bottom layer is considered to be the so-called inner adsorption layer that is not fully swollen with water vapor. This may be because the polymer chains in the inner adsorption layer are strongly constrained onto the substrate, which inhibits water vapor penetration. The polymer chains in this layer have many contact points to the substrate via the hydrogen bonding between the hydroxyl groups in the polymer chain and the silanol groups on the surface of the Si substrate and consequently exhibit extremely slow dynamics. Therefore, it is inferred that the bottom layer is fully amorphous. Furthermore, we consider the middle layer to be somewhat amorphous because parts of the molecular chains are pinned below the interface between the middle and bottom layers. The molecular chains in the top layer become more mobile and ordered, owing to the large distance from the strongly constrained bottom layer; therefore, they exhibit a much lower degree of swelling compared to the middle amorphous layer. Meanwhile, for the PVA with a much lower degree of saponification, the adsorption layer structure consists of the two-layers. The bottom layer forms the inner adsorption layer that moderately swells with water vapor because the polymer chains have few contact points to the substrate. The molecular chains in the middle layer, therefore, are somewhat crystallizable because of this weak constraint.
宮崎 司*; 宮田 登*; 浅田 光則*; 津村 佳弘*; 鳥飼 直也*; 青木 裕之; 山本 勝宏*; 金谷 利治*; 川口 大輔*; 田中 敬二*
Langmuir, 35(34), p.11099 - 11107, 2019/08
被引用回数：22 パーセンタイル：68.53(Chemistry, Multidisciplinary)We investigated the swelling behaviors of poly(vinyl alcohol) (PVA) films deposited on Si wafers with water vapor, which is a good solvent for PVA for elucidating structural and dynamical heterogeneities in the film thickness direction. Using deuterated water vapor, structural and dynamical differences in the thickness direction can be detected easily as different degrees of swelling in the thickness direction by neutron reflectivity. Consequently, the PVA film with a degree of saponification exceeding 98 mol % exhibits a three-layered structure in the thickness direction. It is considered that an adsorption layer consisting of molecular chains that are strongly adsorbed onto the solid substrate is formed at the interface with the substrate, which is not swollen with water vapor compared with the bulk-like layer above it. The adsorption layer is considered to exhibit significantly slower dynamics than the bulk. Furthermore, a surface layer that swells excessively compared with the underneath bulk-like layer is found. This excess swelling of the surface layer may be related to a higher mobility of the molecular chains or lower crystallinity at the surface region compared to the underneath bulk-like layer. Meanwhile, for the PVA film with a much lower degree of saponification, a thin layer with a slightly lower degree of swelling than the bulk-like layer above it can be detected at the interface between the film and substrate only under a high humidity condition. This layer is considered to be the adsorption layer composed of molecular chains loosely adsorbed onto the Si substrate.
玉井 広史; 松川 誠; 栗田 源一; 林 伸彦; 浦田 一宏*; 三浦 友史; 木津 要; 土屋 勝彦; 森岡 篤彦; 工藤 祐介; et al.
Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02
被引用回数：2 パーセンタイル：6.49(Physics, Fluids & Plasmas)JT-60定常高ベータ化計画(JT-60改修計画)の最重要課題は高ベータ,臨界クラスのパラメータを持つ高性能プラズマの100秒程度以上の維持を実証することである。このため、高ベータプラズマを達成するためのプラズマパラメータや運転シナリオ,制御手法の検討を行うとともに、超伝導磁場コイルの要素技術の開発を始め、放射線遮蔽や真空容器等の設計検討及び試験開発を行い、その成立性を確認した。本発表は、以上の物理・工学設計と試験開発の進捗状況を詳述する。
