| 研究課題/領域番号 |
22K14655
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| 研究機関 | 北海道大学 |
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研究代表者 |
黄 瑞康 北海道大学, 電子科学研究所, 助教 (60901296)
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| 研究期間 (年度) |
2022-04-01 – 2024-03-31
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| キーワード | supramolecule / polarity / structural flexibility / pyroelectricity |
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| 研究実績の概要 |
18-crown-6-based supramolecular crystals can exhibit structural flexibility or polarity. For example, nitromethane solvate 18C6 is highly structurally flexible due to Van der Waal interactions between nitromethane and 18C6. Additionally, (4-methoxyanilinium)(18C6)(BF4) shows polarity due to the polar -OCH3 group, allowing the crystal to exhibit piezoelectricity, pyroelectricity, and ferroelectricity. Combining polarity and structural flexibility in an 18C6 crystal is achievable using polar ammoniums with an increased number of -CH2 groups.
Our preliminary study found that that the combination of 3-hydroxyl-adamantane-1-aminium (HADA-OH) with 18C6 produced a crystal that was both structurally flexible and polar due to the -OH group. The polar (HADA-OH)(18C6)ClO4 crystal was found to exhibit both the highest structural flexibility among organic salts and large pyroelectricity (20 times that of PVDF).
This study focuses on HADA-R derivatives (R = H, F, Cl, Br) and examines the effects of different -R groups and counter anions on crystal packing, flexibility, and pyroelectricity. The goal is to establish a relationship between design, structure, and performance in this system and propose a novel strategy for high-performance pyroelectrics for waste heat harvesting.
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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
We synthesized HADA-R derivatives (R = H, F, Cl, Br) and crystals (HADA-R)(18C6)ClO4. They share similar 1D supramolecular columns, but different properties.
1) The H-compound crystallizes in CmC21 at 353-433 K and Pca21 at 113-333 K. At 253-333 K, both HADA-H and 18C6 undergoes rotational-freezing transition, resulting in large thermal expansions. This compound may exhibit pyroelectricity as designed. 2) The F-compound crystallizes in Cmcm at 373 K, Cmc21 at 253 K, and Pca21 at 133 K. The disordered of NH3 and F in the higher-symmetry Cmcm phase, indicates that HADA-F undergoes flipping motion in the 1D supramolecular column. This compound may be a potential 1D ferroelectric.3) The Cl-compound exhibits polymorphism. One polymorphic crystalize in Cmc21. The other crystallizes in Pbca with reverse-arranged columns. We found that this nonpolar crystal exhibits a planar negative-zero-positive thermal expansion transition due to the rotation-swing-static transition of 18-crown-6. We have submitted these results to Chemistry of Materials. 4) The Br-compound crystallizes in Pmma at 333-413 K and P212121 at 113-313 K. This compound did not show significant thermal expansion, which may be due to the large size Br atom that blocking the 18C6 from molecular motion.
Although we found the rich and interesting physical properties in this series, the progress of research on their pyroelectric properties is slightly behind the research plan due to slow crystal growth and rebuilding for the pyroelectric measurement. We plan to accelerate our research progress in the next year.
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| 今後の研究の推進方策 |
Research plan of this year aims to conduct further studies and organize data on the series of (HADA-R)(18C6) crystals. The following aspects will be covered:
For OH-compounds, research data will be summarized and organized into a manuscript for publication. Concurrently, the method of preparing OH-compounds samples on thin films will be explored and the pyroelectric performance of the prepared thin films will be investigated.
For the substitute compounds,1) Large single crystal samples of H-compounds will be prepared and processed into sizes suitable for measurement to obtain their pyroelectric data. 2) Single crystal samples of F compounds will be prepared to explore their phase transition behavior, dielectric properties, and potential ferroelectricity. 3) Methods to obtain different polymorphs of Cl compounds will be explored. The thermal expansion properties of the Cmc21 crystals will be studied, and the possibility of exhibiting pyroelectricity will be investigated.
Additionally, attempts will be made to replace anions with other monovalent anions such as BF4, PF6, CFSSO3, etc., to explore the effects of anions on this series of crystals and prepare for further exploration of this system.
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| 次年度使用額が生じた理由 |
Due to Covid-19, some domestic and international travel has been restricted, which has prevented some collaborative research and participation in academic conferences. In the next fiscal year, we plan to actively promote these activities and make progress in our research.
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