1990 Fiscal Year Final Research Report Summary
Study of Sol-gel Transition using Various NMR Techniques
| Project/Area Number |
01550684
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子物性
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| Research Institution | Hokkaido University |
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Principal Investigator |
HIKICHI Kunio Hokkaido University, Dept. of Polym. Sci. Professor, 理学部, 教授 (30000805)
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| Co-Investigator(Kenkyū-buntansha) |
TSUDA Sakae Hokkaido University, Dept. of Polym. Sci., Technical Assistant, 理学部, 教務職員 (70211381)
TAKEGOSHI Kiyonori Hokkaido University, Dept. of Polym. Sci., Assistant, 理学部, 助手 (10206964)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Nuclear Magnetic Resonance / Gel / Sol-Gel Transition / kappa -Carrageenen / Water / Self-Diffusion Constant / Rb^+ ion / Hysteresis |
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| Research Abstract |
Kappa -Carrageenan gel which is formed by the addition of Rb^+ ion to its aqueous solution undergoes a transition into sol in the vicinity of 55^ﾟC with increasing temperature. In order to examine the behavior of water molecules in the gel, we measured the self-diffusion constant of water molecules by the nuclear magnetic resonance method.
The kappa -carrageenan gel was prepared by adding 50mM RbCl to 5wt% kappa -carrageenan aqueous solution. The self-diffusion constant was measured by the combined use of the Carr-Purcell-Meiboom-Gill method and the field gradient method using JEOL JNM-FX60 equipped with a PL502 field gradient unit. The field gradient unit was calibrated using the known self-diffusion constant of pure water at room temperature.
We measured the temperature dependence of the self-diffusion constant of pure water molecules in the temperature range from 25 to 75^ﾟC. The observed value was found to agree well with the value in the literature. We also measured the temperature dependence of the self-diffusion constant of water molecules of the 5wt% kappa -carrageenan aqueous solution. The values are almost the same as those of pure water.
The temperature dependence of the self-diffusion constant of the kappa -carrageenan gel was measured. It was found that the self-diffusion constant of water molecules in the gel state is smaller than that of pure water, indicating the restricted translational motion of water molecules inside the gel network. In the vicinity of 55^ﾟC where the gel-to-sol transition occurs, the self diffusion constant abruptly increases and approaches the value of pure water. The results indicate that the transition releases the translational freedom of motion of water. When the temperature is lowered, the transition region shifts to lower temperature, showing the hysteresis. The data were found to scatter in the transition region, supposedly implying the critical relaxation.
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