| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2000: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Aqueous mixtures of diols, which have an HO-(CH_2)_n-OH structure, of ethylene glycol (eg), 1,3-propanediol (prd), 1,4-butandiol (bud), and 1,5-pentanediol (ped) have been investigated by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), small-angle neutron scattering (SANS), and ^<17>O-NMR relaxation. The results from DSC measurements revealed that aqueous mixtures of diols (n = 2 and 4) are easily crystallized at low temperature, while those of diols (n = 3 and 5) are kept as a supercooled solution until -100℃. An X-ray diffraction study of a crystal structure of pure diol, which has even number of carbon atoms, showed that the diol molecules easily aggregate via hydrogen bonding. This may be a reason for easy crystallization of aqueous mixtures of diols (n = 2 and 4). From SANS experiments on eg-water mixtures at 25℃ small-angle scattering intensities were not significantly observed, suggesting that ethylene glycol and water molecules are homogeneou
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sly mixed in the solutions. ^<17>O-NMR relaxation measurements on eg-water and prd-water mixtures, where H_2^<17>O is enriched, indicated that T_1 value for each mixture gradually decreases with lowering temperature. It is suggested that the rotational motion of water molecules is gradually restricted with decreasing temperature. In the case of aqueous mixtures of methanol and ethanol, it has been reported that inflection points are observed in plots of T_1 value as a function of mole fraction and the inflection points correspond to structural transition from water structure to hydrogen-bonded alcohol chain. Thus, we concluded that diol and water molecules are more homogeneously mixed in the diol-water mixtures than in methanol-water and ethanol-water ones, i.e. a drastic structural transition scarcely occurs in the diol-water mixtures. This is a reason for that diol-water mixtures can be easily kept at the supercooled state. Now, experiments on diol-water mixtures at high pressures are carrying out by using high pressure NMR cell, which was prepared in this project. Less
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