2005 Fiscal Year Final Research Report Summary
Broadband dielectric spectroscopy and fractal analysis on slow dynamics for molecular complex system
| Project/Area Number |
15340141
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biophysics/Chemical physics
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| Research Institution | Tokai University |
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Principal Investigator |
YAGIHARA Shin Tokai University, School of Science, Professor, 理学部, 教授 (40191093)
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| Co-Investigator(Kenkyū-buntansha) |
SHINYASHIKI Naoki Tokai University, School of Science, Associate Professor, 理学部, 助教授 (00266363)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Molecular complex system / Broadband dielectric spectroscopy / Slow dynamics / Water structure / Polymer aqueous solution / Relaxation time distribution / Fractal structure / Shape parameter |
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| Research Abstract |
A TDR (Time Domain Reflectometry) module and a Precision Impedance Analyzer (Agilent Technology) were employed as sub-systems to set up a new BDS (Broadband Dielectric Spectroscopy) measuring system. Electrodes and temperature jackets were also designed and set up to realize the temperature control within ±3/1000K.
Using the new BDS system, we performed dielecric measurements for poly(vinylpyrrolidone) [PVP] aqueous solutions and various alcohol solutions in wide frequency and temperature regions. Relaxation processes observed for micro-Brownian motions of the PVP chains and solvent dynamics show concentration dependences of relaxation parameters. Increasing density of hydrogen bonding suggests a decrease in the relaxation time and implies a molecular mechanism of the relaxation process related to liquid structures formed by hydrogen bonding.
The Cole-Cole's shape factor related to the relaxation time distribution obtained for water in detergent (C_4E_1)/water systems showed broadening o
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f the distribution in the vicinity of the critical point. The similar broadening was also shown for water interacting with the membrane in the liposome/water system around the phase transition temperature from the preliminary measurements. These results suggest fluctuations of water structure around the phase transition temperature. Developments of more precise dielectric measuring system are expected to clarify these phenomena.
The relaxation time vs. Cole-Cole's shape factor diagram shows characteristic behaviors of water structure reflecting each aqueous system. This behavior is expressed by a trajectory with changing water amount in the diagram. The fractal dimension and other quantities describe this trajectory. It was found that the behaviors for poly(acryl amide) [PAAm]-water/acetone and PAAm-water/1,4-dioxane gels exhibited the same trajectory in the diagram. This result indicates that the water structure reflects the characteristic feature of interacting PAAm chains. These characteristic features are found for some typical aqueous systems, such as polymer aqueous solutions, gels, dispersion systems, biological tissues, and food. It is expected that universal interpretations for characteristic water structures will be clarified in further investigations. Less
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