セルロースナノファイバーの精密構造解析

• Project/Area Number: 21H04733
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 40:Forestry and forest products science, applied aquatic science, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: 齋藤 継之 東京大学, 大学院農学生命科学研究科(農学部), 教授 (90533993)
• Co-Investigator(Kenkyū-buntansha): 小林 加代子 京都大学, 農学研究科, 助教 (00806416)
• Project Period (FY): 2021-04-05 – 2025-03-31
• Project Status: Granted (Fiscal Year 2024)
• Budget Amount: ¥41,600,000 (Direct Cost: ¥32,000,000、Indirect Cost: ¥9,600,000); Fiscal Year 2024: ¥10,140,000 (Direct Cost: ¥7,800,000、Indirect Cost: ¥2,340,000); Fiscal Year 2023: ¥10,140,000 (Direct Cost: ¥7,800,000、Indirect Cost: ¥2,340,000); Fiscal Year 2022: ¥10,140,000 (Direct Cost: ¥7,800,000、Indirect Cost: ¥2,340,000); Fiscal Year 2021: ¥11,180,000 (Direct Cost: ¥8,600,000、Indirect Cost: ¥2,580,000)
• Keywords: セルロースナノファイバー / 結晶性 / 欠陥 / 熱伝導率 / 構造解析 / 原子間力顕微鏡 / 固体核磁気共鳴

Outline of Research at the Start

近年はセルロースナノファイバー（CNF）の量産体制が整い、学術分野においてもCNF関連の論文数が飛躍的に増加している。しかし、そのほとんどがCNFを応用した材料研究であり、CNFの構造理解を進めた論文はわずかである。結果的に当該分野では、確証のない「もっともらしい構造」がCNF１本の構造として浸透しており、仮説に仮説を重ねた議論が散見され、実用化に向けた課題解決や機能開拓にも支障をきたしている。そこで本研究では、「CNF固有の機能・性能に係わる構造（断面形状・表面構造・欠陥分布・結束構造）」を解明し、CNF研究の基盤的知見を整備する。

Outline of Annual Research Achievements

2022年度までの研究で、セルロースナノファイバー（CNF）の断面寸法は、平均すると18本鎖モデル（CNF1本を分子鎖18本が構成するモデル）が妥当である一方、長軸方向の30%～40%の領域で、18本鎖モデルでは説明できない凹み欠陥を有することが判明した。2023年度は、この凹み欠陥の分布解析に注力した。その結果、凹み欠陥の約70％以上が、CNFの屈曲部や端点に局在化していることが判明した。また、屈曲部や端点の凹みは、その他直線部の凹みよりも、深い形状をしていた。さらに、CNFの長さが短くなるにつれ、屈曲部の割合が減少する傾向が見出された。一連の結果をもとに、CNFの生産工程における破断機構を考察した。まず、深い凹み欠陥が形成され、その領域が屈曲部となったのち、破断し、端点を形成するという機構を想定した。
表面構造の解析に関しては、試行錯誤が続いており、2024年度内に成果をまとめる計画である。現状、CNFを原子間力顕微鏡で液中観察する際、イオン化した官能基の水和構造が大きく、動きやすいため、観察しにくいことが判明している。
また、結束構造（結晶子合一）の解析についても、2022年度以降、継続して検討を進めてきた。結束構造の形成機構を理解するため、CNF分散液を徐々に脱水し、固形分率の異なるCNF試料を調製した。これらの試料について、CNFの結晶性を多角的に解析したところ、CNFの部分的な結束は、1％以下の低固形分濃度において著しく進み、1％に達すると安定なCNFの網目構造を形成すること、そして、さらに脱水を進めると、結束部を基点としてCNF間の会合が徐々に進んでいくことが示唆された。

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

欠陥部の解析に関しては、計画書に記載の通り、2023年度内に分布解析を完了することができた。分子量との相関については、2024年度にまとめる予定である。表面構造の解析がやや難度が高いものの、2023年度に糸口が見えたため、計画通り、2024年度内には達成できる見込みである。また、2022年度以降も継続して検討を続けてきた結束構造の解析に関しても、当初の計画よりも踏み込んだ成果が得られており、CNF材料の理解をさらに深めることができた。

Strategy for Future Research Activity

2024年度は、CNFの表面構造解析と、欠陥と分子量の相関を解析する予定である。

Research Products

• [Int'l Joint Research] Stockholm University(スウェーデン)
• [Journal Article] Low solid content mouldable chitin physical hydrogel prepared by atypical rupture-free swelling (2024)
  • Author(s): Kaku Yuto、Okada Satoshi、Fujisawa Shuji、Saito Tsuguyuki、Isobe Noriyuki
  • Journal Title: Soft Matter Volume: 20 Issue: 6 Pages: 1245-1252
  • DOI: 10.1039/d3sm01542d
  • Peer Reviewed
• [Journal Article] Elucidation of the Specific Ion Effects and Intermediate Structures of Cellulose Fibers Swollen in Inorganic Salt Solutions via In Situ X-ray Diffraction (2024)
  • Author(s): Kobayashi Kayoko、Isobe Noriyuki、Kusumi Ryosuke、Nemoto Junji、Wada Masahisa
  • Journal Title: Biomacromolecules Volume: 25 Issue: 2 Pages: 864-870
  • DOI: 10.1021/acs.biomac.3c01016
  • Peer Reviewed / Open Access
• [Journal Article] Adsorption properties of cellulose beads prepared by emulsion-gelation method and subsequent oxidation (2024)
  • Author(s): Zhang Yangyang、Kobayashi Kayoko、Kusumi Ryosuke、Kim Ung-Jin、Wada Masahisa
  • Journal Title: Colloids and Surfaces A: Physicochemical and Engineering Aspects Volume: 682 Pages: 132859-132859
  • DOI: 10.1016/j.colsurfa.2023.132859
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Molecular Dynamics of Drying‐Induced Structural Transformations in a Single Nanocellulose (2023)
  • Author(s): Fujisawa Shuji、Daicho Kazuho、Yurtsever Ayhan、Fukuma Takeshi、Saito Tsuguyuki
  • Journal Title: Small Volume: 19 Issue: 30 Pages: 2302276-2302276
  • DOI: 10.1002/smll.202302276
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Morphological Changes of Polymer-Grafted Nanocellulose during a Drying Process (2023)
  • Author(s): Fujisawa Shuji、Daicho Kazuho、Yurtsever Ayhan、Fukuma Takeshi、Saito Tsuguyuki
  • Journal Title: Biomacromolecules Volume: 24 Issue: 8 Pages: 3908-3916
  • DOI: 10.1021/acs.biomac.3c00530
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Monitoring crystallite fusion of nanocellulose during colloid condensation (2023)
  • Author(s): Doi Yoshinori、Daicho Kazuho、Isobe Noriyuki、Tanaka Reina、Kimura Satoshi、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Cellulose Volume: 30 Issue: 13 Pages: 8287-8297
  • DOI: 10.1007/s10570-023-05354-x
  • Peer Reviewed / Open Access
• [Journal Article] Property-Thickness Correlations of Transparent All-Nanocellulose Laminates (2023)
  • Author(s): Ishioka Shun、Hirano Takayuki、Matoba Nobuhiro、Isobe Noriyuki、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Journal of Fiber Science and Technology Volume: 79 Issue: 7 Pages: 156-164
  • DOI: 10.2115/fiberst.2023-0020
  • ISSN: 2189-7654
  • Peer Reviewed / Open Access
• [Journal Article] Catalytic Properties of Nanochitin-Shelled Polymer Microparticles in Knoevenagel Condensation (2023)
  • Author(s): Kaku, Y.; Isobe, N.; Saito, T.; Fujisawa, S.
  • Journal Title: Chitin and Chitosan Research Volume: 29 Pages: 3-7
  • Peer Reviewed
• [Journal Article] α-d-(1→3)-graft-(1→6)-glucan: Comb-like polysaccharide synthesized in vitro with α-1,3/1,6-glucosyltransferase L from Streptococcus salivarius (2023)
  • Author(s): Kusumi Ryosuke、Asai Shinichi、He Qinfeng、Kobayashi Kayoko、Kimura Satoshi、Yoshida Makoto、Wada Masahisa
  • Journal Title: Carbohydrate Research Volume: 534 Pages: 108969-108969
  • DOI: 10.1016/j.carres.2023.108969
  • Peer Reviewed
• [Journal Article] Biodegradation of various forms of cellulose and chitin in natural waters with different salinity (2023)
  • Author(s): Miyaji Koki、Zhou Chunfan、Maeda Asahi、Kobayashi Kayoko、Kusumi Ryosuke、Wada Masahisa
  • Journal Title: Polymer Degradation and Stability Volume: 215 Pages: 110423-110423
  • DOI: 10.1016/j.polymdegradstab.2023.110423
  • Peer Reviewed
• [Journal Article] Effect of nanocellulose length on emulsion stabilization and microparticle synthesis (2023)
  • Author(s): Fujisawa Shuji、Tanaka Reina、Hayashi Yumi、Yabuhara Yasushi、Kume Makoto、Saito Tsuguyuki
  • Journal Title: Polymer Journal Volume: 55 Issue: 3 Pages: 223-228
  • DOI: 10.1038/s41428-022-00748-3
  • Peer Reviewed
• [Journal Article] Fully Wood-Based Transparent Plates with High Strength, Flame Self-Extinction, and Anisotropic Thermal Conduction (2023)
  • Author(s): Ishioka Shun、Isobe Noriyuki、Hirano Takayuki、Matoba Nobuhiro、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: ACS Sustainable Chemistry & Engineering Volume: 11 Issue: 6 Pages: 2440-2448
  • DOI: 10.1021/acssuschemeng.2c06344
  • Peer Reviewed / Open Access
• [Journal Article] Evaluating the Emulsifying Capacity of Cellulose Nanofibers Using Inverse Gas Chromatography (2023)
  • Author(s): Yagita Tomohito、Ito Tomoki、Hirano Takayuki、Toyomasu Takayuki、Hasegawa Sai、Saito Tsuguyuki、Fujisawa Shuji
  • Journal Title: Langmuir Volume: 39 Issue: 12 Pages: 4362-4369
  • DOI: 10.1021/acs.langmuir.2c03369
  • Peer Reviewed
• [Journal Article] Chitin nanofiber-coated biodegradable polymer microparticles via one-pot aqueous process (2023)
  • Author(s): Kaku Yuto、Isobe Noriyuki、Ogawa Nanako O.、Ohkouchi Naohiko、Ikuta Tetsuro、Saito Tsuguyuki、Fujisawa Shuji
  • Journal Title: Carbohydrate Polymers Volume: 312 Pages: 120828-120828
  • DOI: 10.1016/j.carbpol.2023.120828
  • Peer Reviewed
• [Journal Article] Counterion-Dependent Material Properties of Phosphorylated Nanocellulose (2023)
  • Author(s): Zhao Mengchen、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Biomacromolecules Volume: 24 Issue: 4 Pages: 1881-1887
  • DOI: 10.1021/acs.biomac.3c00066
  • Peer Reviewed
• [Journal Article] Atomic-scale dents on cellulose nanofibers: the origin of diverse defects in sustainable fibrillar materials (2022)
  • Author(s): Ito Tomoki、Daicho Kazuho、Fujisawa Shuji、Saito Tsuguyuki、Kobayashi Kayoko
  • Journal Title: Nanoscale Horizons Volume: 7 Issue: 10 Pages: 1186-1191
  • DOI: 10.1039/d2nh00355d
  • Peer Reviewed / Open Access
• [Journal Article] Structure of Polymer-Grafted Nanocellulose in the Colloidal Dispersion System (2022)
  • Author(s): Fujisawa Shuji、Takasaki Yuichi、Saito Tsuguyuki
  • Journal Title: Nano Letters Volume: 23 Issue: 3 Pages: 880-886
  • DOI: 10.1021/acs.nanolett.2c04138
  • Peer Reviewed / Open Access
• [Journal Article] Linear Correlation between True Density and Crystallinity of Regenerated and Mercerized Celluloses (2022)
  • Author(s): Daicho Kazuho、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Biomacromolecules Volume: 24 Issue: 2 Pages: 661-666
  • DOI: 10.1021/acs.biomac.2c01067
  • Peer Reviewed
• [Journal Article] Cellulose fiber biodegradation in natural waters: river water, brackish water, and seawater (2022)
  • Author(s): Nagamine Ryo、Kobayashi Kayoko、Kusumi Ryosuke、Wada Masahisa
  • Journal Title: Cellulose Volume: 29 Issue: 5 Pages: 2917-2926
  • DOI: 10.1007/s10570-021-04349-w
  • Peer Reviewed
• [Journal Article] Comparative characterization of phosphorylated wood holocelluloses and celluloses for nanocellulose production (2021)
  • Author(s): Zhao Mengchen、Ono Yuko、Noguchi Yuichi、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Cellulose Volume: 29 Issue: 5 Pages: 2805-2816
  • DOI: 10.1007/s10570-021-04013-3
  • Peer Reviewed
• [Journal Article] Recovery of the Irreversible Crystallinity of Nanocellulose by Crystallite Fusion: A Strategy for Achieving Efficient Energy Transfers in Sustainable Biopolymer Skeletons** (2021)
  • Author(s): Daicho Kazuho、Kobayashi Kayoko、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Angewandte Chemie International Edition Volume: 60 Issue: 46 Pages: 24630-24636
  • DOI: 10.1002/anie.202110032
  • Peer Reviewed / Open Access
• [Journal Article] Nanocellulose Xerogel as Template for Transparent, Thick, Flame-Retardant Polymer Nanocomposites (2021)
  • Author(s): Sakuma Wataru、Fujisawa Shuji、Berglund Lars A.、Saito Tsuguyuki
  • Journal Title: Nanomaterials Volume: 11 Issue: 11 Pages: 3032-3032
  • DOI: 10.3390/nano11113032
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Distribution and Quantification of Diverse Functional Groups on Phosphorylated Nanocellulose Surfaces (2021)
  • Author(s): Zhao Mengchen、Fujisawa Shuji、Saito Tsuguyuki
  • Journal Title: Biomacromolecules Volume: 22 Issue: 12 Pages: 5214-5222
  • DOI: 10.1021/acs.biomac.1c01143
  • Peer Reviewed / Open Access
• [Journal Article] Three-dimensional alignment of cellulose II microcrystals under a strong magnetic field (2021)
  • Author(s): Wada Masahisa、Wakiya Sayuri、Kobayashi Kayoko、Kimura Satoshi、Kitaoka Motomitsu、Kusumi Ryosuke、Kimura Fumiko、Kimura Tsunehisa
  • Journal Title: Cellulose Volume: 28 Issue: 11 Pages: 6757-6765
  • DOI: 10.1007/s10570-021-03954-z
  • Peer Reviewed
• [Presentation] Heat-insulating yet light-permeable, and mechanically tough cryogels of wood nanocellulose (2024)
  • Author(s): Xinyi Hou, Junki Kotsuka, Wataru Sakuma, Tomoki Ito, Zhifang Sun, Shuji Fujisawa, and Tsuguyuki Saito
  • Organizer: ACS Spring 2024 Meeting
  • Int'l Joint Research / Invited
• [Presentation] 界面制御によるセルロースナノファイバー材料の特性発現 (2024)
  • Author(s): 齋藤継之
  • Organizer: 日本接着学会中部支部・接着講座マスターコース
  • Invited
• [Presentation] 機能性ナノセルロース (2024)
  • Author(s): 齋藤継之
  • Organizer: Nanocellulose Symposium Final
  • Invited
• [Presentation] Structuring of cellulose nanofibers for producing functional materials (2023)
  • Author(s): Tsuguyuki Saito, Shuji Fujisawa, Kazuho Daicho, Wataru Sakuma, Shun Ishioka
  • Organizer: The 13th SPSJ International Polymer Conference
  • Int'l Joint Research / Invited
• [Presentation] TEMPO酸化CNFの構造制御と機能展開 (2023)
  • Author(s): 齋藤継之
  • Organizer: 第6期ナノセルロース塾
  • Invited
• [Presentation] Monitoring crystallite fusion of nanocellulose in network densification (2023)
  • Author(s): Tsuguyuki Saito, Yoshinori Doi, Kazuho Daicho
  • Organizer: 5th Stockholm-Tokyo Workshop
  • Int'l Joint Research / Invited
• [Presentation] Transparent, High-Strength, and Moldable Plates of Self-Adhesive Nanocellulose Laminate (2022)
  • Author(s): Tsuguyuki Saito, Shun Ishioka
  • Organizer: Nanocellulose Seminar at Royal Institute of Technology
  • Int'l Joint Research / Invited
• [Presentation] Pursuing the potential of cellulose nanofibers through assembly controls (2022)
  • Author(s): Tsuguyuki Saito, Kazuho Daicho, Wataru Sakuma, Shun Ishioka
  • Organizer: Nanocellulose days 2022
  • Int'l Joint Research / Invited
• [Presentation] Recent progress in structural understanding of cellulose nanofibers (2022)
  • Author(s): Tsuguyuki Saito, Kazuho Daicho
  • Organizer: Eco-friendly Polymeric Materials Seminar
  • Int'l Joint Research / Invited
• [Presentation] CNF学術研究の新局面：構造理解と成形加工の大転換 (2022)
  • Author(s): 齋藤継之
  • Organizer: 化学工業日報・CNF特別講演会
  • Invited
• [Presentation] 農学と木とナノテクノロジー (2022)
  • Author(s): 齋藤継之
  • Organizer: 埼玉県立大宮高等学校・大学セミナー
  • Invited
• [Presentation] TEMPO酸化CNFの結晶性制御と欠陥構造, 及びフィルム・多孔体・複合体の最新成果 (2022)
  • Author(s): 齋藤継之
  • Organizer: 富士市CNFプラットフォームセミナー
  • Invited
• [Presentation] TEMPO酸化CNFの構造制御と機能展開 (2022)
  • Author(s): 齋藤継之
  • Organizer: ナノセルロースジャパン・ナノセルロース塾第5期
  • Invited
• [Presentation] セルロースナノファイバーの構造解析と成形加工の最先端 (2022)
  • Author(s): 齋藤継之
  • Organizer: 第16回多糖の未来フォーラム
  • Invited
• [Presentation] Mechanicaly strong, scalable xerogels of nanocellulose featuring light permeability, thermal insulation, and flame self-extinction (2021)
  • Author(s): Tsuguyuki Saito, Wataru Sakuma
  • Organizer: ACS Spring 2021, A Century of Cellulose: The Past, Present, andFuture of Cellulose and Renewable Materials
  • Int'l Joint Research / Invited
• [Presentation] TEMPO-oxidized CNF and related materials (2021)
  • Author(s): Tsuguyuki Saito
  • Organizer: Wallenberg Wood Science Center (WWSC) annual workshop
  • Int'l Joint Research / Invited
• [Presentation] Controlling Dispersion and Assembly of Cellulose Nanofibers (2021)
  • Author(s): Tsuguyuki Saito, Kazuho Daicho, Wataru Sakuma
  • Organizer: The 7th European Polysaccharide Network of Excellence (EPNOE)
  • Int'l Joint Research / Invited
• [Presentation] Cellulose nanofiber: a wood-derived versatile building block (2021)
  • Author(s): Tsuguyuki Saito
  • Organizer: UTokyo-NTU Online Joint Conference
  • Int'l Joint Research / Invited
• [Presentation] Assembly-induced recovery of the crystallinity of cellulose nanofibers (2021)
  • Author(s): Tsuguyuki Saito, Kazuho Daicho
  • Organizer: ACS Spring 2022, Anselme Payen Award Symposium
  • Int'l Joint Research / Invited
• [Remarks] セルロースナノファイバーから、アルミニウム合金並の強度と自己消火性を兼ね備えた、透明な板材を開発
  • URL: https://www.a.u-tokyo.ac.jp/topics/topics_20230217-1.html
• [Remarks] セルロースナノファイバーに生じた原子レベルの欠陥構造を発見
  • URL: https://www.a.u-tokyo.ac.jp/topics/topics_20221006-1.html