2019 Fiscal Year Annual Research Report
配向セルロースナノファイバーを内包する伸縮性の高引張強度エアロゲル
| Project/Area Number |
19F19100
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| Research Institution | The University of Tokyo |
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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), 准教授 (90533993)
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| Co-Investigator(Kenkyū-buntansha) |
SUN ZHIFANG 東京大学, 農学生命科学研究科, 外国人特別研究員
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| Project Period (FY) |
2019-04-25 – 2021-03-31
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| Keywords | cellulose nanofibril / condensation / aerogel / tensile strength / orientation |
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| Outline of Annual Research Achievements |
Cellulose nanofibrils (CNFs) possess high aspect ratios, and their dispersions thus intrinsically show very high viscosity at relatively low concentrations. However, high viscosity severely limits their processability, and a desired bulk concentration higher than 2.0 wt% is challenging in the nanocellulose science.
In the present study, we have discovered a new, facile, scalable and controllable method to get CNFs at any concentrations. All of the condensed CNF materials are highly homogeneous. Slicing and peeling of the condensed CNF hydrogel produces a lot of thin gel layers, indicating it is highly anisotropic, with CNFs orient in the in-plane direction. The SAXS profile and SEM images exclusively support such layered orientation. Further gelation of the condensed CNF hydrogels by protonation (H+) or coordination (Al3+) affords a series of transparent and strong hydrogels with water content of 70-90%, which exhibit tensile strength and modulus more than 9 MPa and 480 MPa, respectively. The water content, strength and modulus are very close or even superior to those of muscles and cartilages and would very promising in the biomedical applications. When dried by supercritical method, I obtained a series of CNF aerogels which is stretchable over 20%, with tensile strength and modulus reach 8 MPa and 100 MPa, respectively, yet still possess very low thermal conductivity at 19.3 mW m-1 K-1. Our aerogels, both strong and superinsulating, set a new region in the Ashby plots regarding strength and thermal conductivity.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In this JSPS project, our goal is to obtain stretch-tolerant, high tensile strength aerogels using oriented cellulose nanofibrils without sacrificing their extremely low thermal conductivity. Through this research, we're going to address fundamental issues on tensile behaviors of aerogels and establish systematic characterizations for them.
In the current progress, we have discovered a facile, practical, controllable and general method to get condensed cellulose nanofibrils with high structural orientation. Upon supercritical drying, we obtained a series of CNF aerogels which are stretchable for over 20%, with tensile strength and modulus reach 8 MPa and 100 MPa, respectively, yet still possess very low thermal conductivity at 19.3 mW m-1 K-1. Therefore, our research is now progressing as expected.
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| Strategy for Future Research Activity |
For the future plan, we’re going to complete this project and address the following issues. First, we’re going to use the polarized optical microscopy to visualize the condensation and alignment process of cellulose nanofibril dispersion, and find a theory to explain the condensation process. Second, we’re going to systematically characterize the structural, mechanical and thermal properties of the resultant materials, and explain the tensile behavior of the aerogels in the point of view of their unique structures. Finally, we’re going to summarize all of the above data, and prepare patent and manuscript.
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Research Products
(2 results)
