Neutron reflectivity study on the nanostructure of PMMA chains near substrate interfaces based on contrast variation accompanied with small molecule sorption

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

https://doi.org/10.1039/D2SM01482C

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.

Neutron reflectivity study on the suppression of interfacial water accumulation between a polypropylene thin film and Si substrate using a silane-coupling agent

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

https://doi.org/10.1021/acs.langmuir.2c01599

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 25C 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.

Neutron reflectometry-based structural analysis of an aligning agent additive for the alignment of nematic liquid crystals on solid substrates

根本 文也*; 山田 悟史*; 日野 正裕*; 青木 裕之; 瀬戸 秀樹*

Soft Matter, 18(3), p.545 - 553, 2022/01

https://doi.org/10.1039/D1SM01355F

Surface aligning agents, such as amphiphilic surfactants, are widely used to control the initial alignment of nematic liquid crystals (NLCs) in liquid crystal displays (LCDs). Generally, these agents are first coated on a substrate prior to NLC introduction. When mixed with NLCs, long alkyl chain amphiphilic agent additives may control the NLC alignment without requiring pretreatment because they may spontaneously form an adsorbed layer at the solid-NLC interface. These self-assembled layers (SALs) appear promising in the effective control of the initial alignment of LCDs. However, direct observation of the adsorbed layer structure in contact with the NLCs is challenging due to probe limitations. Furthermore, the areal densities and alignments of the amphiphiles adsorbed from NLCs at the solid-NLC interface are not previously reported. Herein, the structure of the surface aligning agent -hexadecyltrimethylammonium-d bromide (d-CTAB) was investigated at the silicon-NLC interface using neutron reflectometry (NR), which indicated that the CTAB self-assembled as a monolayer, with its alignment dependent on the amphiphile concentration. At low amphiphile concentrations, the alignment of the SAL and NLCs was parallel to the substrate. With increasing amphiphile concentration, the number of amphiphiles attached to the substrate increased within the framework of the Gibbs monolayer, with the alignment of the amphiphiles and NLCs becoming perpendicular to the substrate. The experimental setup used here is comparable to those of more natural systems, such as those found in the alignment of NLCs in LCDs.

Neutron reflectivity on the mobile surface and immobile interfacial layers in the poly(vinyl acetate) adsorption layer on a Si substrate with deuterated toluene vapor-induced swelling

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

https://doi.org/10.1021/acs.langmuir.0c03025

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.

MLF将来計画技術検討会・中性子実験装置発表資料集

中島 健次; Harjo, S.; 山田 悟史*; 及川 健一; 梶本 亮一

JAEA-Review 2018-032, 43 Pages, 2019/02

JAEA-Review-2018-032.pdf:9.78MB

大強度陽子加速器施設(J-PARC)物質・生命科学実験施設(MLF)では2017年より「MLF将来計画技術検討会」が設置され、MLFの線源や実験装置の将来計画について議論が行われてきた。同検討会では中性子実験装置についても装置カテゴリ毎に現状の問題点や今後目指すべき方向性についての報告がなされた。本報告書は、今後の将来計画の検討の一助とするべく、同検討会におけるMLF中性子実験装置に関する発表資料をまとめたものである。

Dynamical behavior of human -synuclein studied by quasielastic neutron scattering

藤原 悟; 荒木 克哉*; 松尾 龍人; 八木 寿梓*; 山田 武*; 柴田 薫; 望月 秀樹*

PLOS ONE (Internet), 11(4), p.e0151447_1 - e0151447_17, 2016/04

https://doi.org/10.1371/journal.pone.0151447

Filamentous aggregates (amyloid fibrils) of the protein -synuclein (-Syn) are related to the pathogenesis of Parkinson's disease. To understand the pathogenesis mechanism of this disease, the mechanism of the amyloid fibril formation of -Syn must be elucidated. As a first step toward this ultimate goal, dynamical behavior of -Syn in the monomeric and the fibril states was investigated using quasielastic neutron scattering (QENS). Analysis of the QENS spectra of solution samples of -Syn shows that diffusive global motions are observed in the monomeric state but largely suppressed in the fibril state. However, the amplitude of the side chain motion is shown to be larger in the fibril state than in the monomeric state. This implies that significant solvent space exists within the fibrils, which is attributed to the -Syn molecules within the fibrils having a distribution of conformations. The larger amplitude of the side chain motion in the fibril state than in the monomeric state implies that the fibril state is entropically favorable.

放射性廃棄物の処理

小澤 一茂; 山田 悟志

放射線業務従事者再教育訓練テキスト, p.133 - 150, 2011/00

核燃料物質及び核燃料物質に汚染された物の取扱いに関するもののうち、「放射性廃棄物の処理」について、放射能レベル,性状ごとに、固体廃棄物及び液体廃棄物の処理方法等を取りまとめたものであり、原子力科学研究所放射性廃棄物処理場における各々の設備・機器を中心に処理方法等を解説するものである。これにより、核燃料物質等(廃棄物)の運搬,貯蔵,廃棄の作業方法に関すること、放射性廃棄物の取扱い,核燃料物質等によって汚染された物の取扱いに関する知識を習得できるものである。

Crystal structure of frustrated antiferromagnet UNiB

芳賀 芳範; 小山田 明*; 松田 達磨; 池田 修悟; 大貫 惇睦

Physica B; Condensed Matter, 403(5-9), p.900 - 902, 2008/04

https://doi.org/10.1016/j.physb.2007.10.232

UNiBは反強磁性体と報告されている。その磁性は異常で、絶対零度でも部分的に秩序しないモーメントが残ると考えられている。その起源は、hexagonal結晶構造に起因する相互作用のフラストレーションにあるとされている。本研究では、この物質の純良単結晶を育成し、その結晶構造を解明することにより磁性の異常を考察した。単結晶X線回折により、微小な超格子反射が観測された。詳しい積分強度の解析から、正確な結晶構造は斜方晶に属し、厳密な意味でのフラストレーションは存在しないことが明らかとなった。

Highly polarized cold neutron beam obtained by using a quadrupole magnet

奥 隆之; 山田 悟; 篠原 武尚; 鈴木 淳市; 三島 賢二*; 広田 克也*; 佐藤 広海*; 清水 裕彦

Physica B; Condensed Matter, 397(1-2), p.188 - 191, 2007/07

https://doi.org/10.1016/j.physb.2007.02.055

四極磁石を用いた中性子偏極装置の開発研究を行っている。中性子が四極磁石内に入射すると、磁石が形成する磁場勾配により、正極性成分と負極性成分が空間的に分離する。そこで、そのうちの一成分を抽出することにより、偏極中性子ビームを得るものである。この方法では、中性子が物質により散乱されたり、吸収されたりすることがないため、非常に高い偏極度の中性子ビームを高効率で得ることが可能である。これまでに、四極永久磁石を用いて冷中性子ビームの偏極実験を行った結果、偏極度P0.999を達成することに成功した。会議では、実験結果の詳細について発表するほか、この偏極装置の中性子散乱実験への応用方法について議論する予定である。

Extended steady-state and high-beta regimes of net-current free heliotron plasmas in the large helical device

本島 修*; 山田 弘司*; 小森 彰夫*; 大藪 修義*; 金子 修*; 川端 一男*; 三戸 利行*; 武藤 敬*; 居田 克巳*; 今川 信作*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 12 Pages, 2007/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/node31.htm#5947

大型ヘリカル装置(LHD)では、加熱パワーの増大及び粒子の排気/供給能力の向上と併せ、無電流ヘリオトロンプラズマの革新的な運転シナリオの開発を行った。その結果、高密度,長時間運転,高ベータに関して運転領域を拡大することに成功した。LHDにおける多様な研究の結果、無電流ヘリオトロンプラズマの特長が明らかになった。特に、ローカルアイランドダイバータによる排気とペレット入射によるプラズマ中心部への粒子供給を組合せることにより内部拡散障壁(IDB)を形成し、mという超高密度のプラズマが得られた。この結果は魅力的な超高密度核融合炉へ道を開くものである。また、4.5%の体積平均ベータ値や、54分間(総入力エネルギー: 1.6GJ,平均パワー: 490kW)の放電維持時間を得ることにも成功した。本論文では、IDB,高ベータプラズマ,長時間運転に関する最近2年間の成果を概括する。