| 研究課題/領域番号 |
20K03887
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| 研究機関 | 早稲田大学 |
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研究代表者 |
GUEGAN Regis 早稲田大学, 理工学術院, 准教授(任期付) (50822483)
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| 研究分担者 |
山田 貴壽 国立研究開発法人産業技術総合研究所, 材料・化学領域, 主任研究員 (30306500)
畠山 一翔 国立研究開発法人産業技術総合研究所, 材料・化学領域, 研究員 (30773965)
菅原 義之 早稲田大学, 理工学術院, 教授 (50196698)
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| 研究期間 (年度) |
2020-04-01 – 2023-03-31
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| キーワード | nanosheets / colloids / hierarchical assemblies / nonionic surfactants / excluded volume |
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| 研究実績の概要 |
The assemblies of colloids formed by the mixtures of the graphene oxide (GO) sheets (with different lateral size and oxidation rate) with alkyl polyethylene oxide ether nonionic surfactants (the dodecyl octaethylene oxide ether C12E8) was investigated for different concentrations of both systems and experimental conditions (temperature and shear rate measurements). The colloidal mixtures were studied by different complementary techniques (Small angle X-ray scattering -SAXS, polarized optical microscopy, rheological measurements, rheo-SANS). From the whole data, the lateral size of GO appears to be an important parameter as well as the oxidation rate in the phase reorganization of L1 phase (spherical micelles) of the nonionic surfactants to hexagonal assemblies (H1 phase). This phase transition (L1 to H1) without any changes of the micelle curvature between the two phases occurs for lower volume fraction that that of the bulk C12E8-water system due to excluded volume effects (entropic effects) induced by the presence of the inorganic sheets (i.e. the volume occupied by GO sheets associating with that one of water in interaction with the hydrophilic is not accessible to the C12E8-H2O, increasing locally the volume fraction of the rigid spherical micelles self-organizing on a hexagonal lattice) much more than the surface geometry of the nanosheets that appear to play a minor role in the morphology control of the C12E8 assemblies.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Different types of GO (prepared by an improved and modified Hummer’s method) from different graphite sources (different lateral sizes) were prepared at Waseda University. The resulting GO nanosheets were characterized by a set of complementary techniques (AFM, SEM, TEM, XPS, XRD and Raman scattering) and show for some of them very large lateral size (close to 100 micrometers). The association of the C12E8 to GO dispersions showing some birefringent properties due to the formation of a nematic phase was studied by small angle X-ray scattering -SAXS (performed at the NIMS, Tsukuba), polarized optical microscopy (Waseda University), rheological measurements (NIMS, Tsukuba), rheo-SANS (J-parc for different temperature and shear-rate conditions. Both lateral size and oxidation rate of GO nanosheets contribute to change the phase diagram of the C12E8 with in particular a phase transition L1-H1 that occurs at lower volume fraction of the C12E8 (22% lower than the bulk C12E8-H2O). In addition, the presence of large GO stabilizes the C12E8-H2O assemblies by extending their phase domain in temperature.
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| 今後の研究の推進方策 |
A complete understanding of the phase reorganization of the nonionic surfactant species will be done by the study of other amphiphilic molecules of the CnEm series and probably other nonionic surfactants and even other nonionic systems showing a L1-H1 phase transition. Indeed, the hydrophilic-lipophilic balance (HLB) as well as the aggregation number (number of surfactants forming micelles) tune the rigidity of the micelles and even their ability to aggregate. Rigid micelles are likely to be more sensitive to excluded volume in contrast to flexible micelles incorporating a large number of surfactants. In addition to the amphiphilic molecules, an improvement of the GO synthesis for a more accurate and monodisperse selection of the lateral size has to be undertaken. Indeed, the ability of the inorganic nanosheets to form the liquid crystalline phase mainly depend on the lateral size as well as its polydispersity.
Further rheological measurements will be done on the colloidal mixtures as well as small angle light scattering measurements and measurements with the use of SAXS, rheo-SANS.
A tentative alignment of the GO nanosheets will be investigated as well with the use of electrodeposition technique onto graphite electrodes or other substates that will be compared to traditional and conventional Langmuir-Blodgett technique to align nanosheets.
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| 次年度使用額が生じた理由 |
Since a lot of experiments were and are planned to be done in the frame of some collaborations, we plan to use the funds to cover the business trips to carry out them at the NIMS in Tsukuba (SAXS, rheological measurements), and/or at the CROSS in Tokai (SALS, rheological measurements as well) and probably in Kobe (Jelena Muncan, Kobe U.).
In addition, since we want to emphasize the universality of the phase reorganization of the nonionic surfactants, several chemicals will be purchased as well as glassware’s or other equipment’s for the synthesis of GO.
Depending on the observations for the deposition and organization of the colloidal mixtures, a Langmuir-Blodgett equipment (noy yet decided) may be finally purchased within this project.
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