2023 Fiscal Year Research-status Report
Design hierarchical structure of mixed carrageenan gels for controlling mechanical properties
| Project/Area Number |
23K12678
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Geonzon Lester 東京大学, 物性研究所, 特任研究員 (60869543)
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| Project Period (FY) |
2023-04-01 – 2026-03-31
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| Keywords | carrageenan / rheology / neutron scattering / x-ray scattering / Particle tracking / LAOS |
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| Outline of Annual Research Achievements |
The research aimed to elucidate the hierarchical structure of kappa (KC), iota (IC) carrageenan gels and their mixtures which is important to control the mechanical properties of the gels. In FY2023, experiments on the rheological property of the gels from linear to nonlinear regime were conducted. The origin of the nonlinear rheological property of the carrageenan gels as well as its mixtures were understood based on the response of the carrageenan aggregates under deformation. We also revealed the spatial and temporal characteristics of KC, IC gels, and their mixtures using SAXS/SANS and NMR. Additionally, the effect of a low molecular weight lambda (LC) on the rheological property of KC gels was investigated. It was suggested that the network structure of the carrageenan gels mixed with low molecular weight LC chains formed a homogenous network leading to the possibility of a swollen KC network in the LC solution.
In FY2023, we are able to characterize the carrageenan gels and their mixtures with similar and different molecular weights. The research results were presented at international and local conferences and published 2 peer-reviewed articles in scientific journals.
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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
The research study has progressed smoothly in FY2023. The experiments on rheological properties, small angle neutron/Xray scattering (SANS/SAXS), nuclear magnetic resonance (pulsed-NMR), and particle tracking of carrageenan gels were performed. The rheological properties of carrageenan gels prepared with potassium chloride were characterized from linear to nonlinear regimes and were correlated with the spatiotemporal characteristics of the network. As for Iota carrageenan (IC) gels, they demonstrated strain stiffness under large deformation, whereas kappa carrageenan (KC) gels exhibited brittle properties and broke at meager strain amplitude. The weak and strain stiffness in IC gels was attributed to the formation of small and flexible IC aggregates, which stretch under large deformation. Conversely, the brittle response of KC gels was linked to the creation of rigid aggregates, which are fragile and break under minimal strain amplitude. We also studied the mixtures of KC and low molecular weight lambda carrageenan gels.
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| Strategy for Future Research Activity |
The in-situ structural analysis of carrageenan gels will be performed under stretching using neutron/X-ray scattering techniques in FY2024. Based on the result in FY2023, the strain stiffening was attributed to the stretching of carrageenan aggregates. An in-situ SANS/SAXS measurement under stretching should reveal the molecular rearrangement of the aggregates. Such phenomena are crucial in understanding the origin of the strain stiffening. Also, the rheological properties and structure of carrageenan gels with different cations will be evaluated. We believe that ion species will affect the properties of carrageenan gels. Furthermore, the properties of carrageenan gels mixed with hybrid carrageenan of different types and controlled molecular weight will be studied using rheology, SANS, NMR, and particle tracking techniques. As established from the previous results, these techniques are useful to clarify the network structure of the carrageenan mixed gels which is crucial in controlling the mechanical properties of the gels.
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