Temperature and Pressure Effect on Cluster Formation in Diol-Water Mixtures

温度和压力对二醇-水混合物中簇形成的影响

基本信息

批准号：
12640500
负责人：
TAKAMUKU Toshiyuki
金额：
$ 2.24万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

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 … More 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

具有HO-(CH_2)_n-OH结构的二醇的水性混合物，包括乙二醇(eg)、1,3-丙二醇(prd)、1,4-丁二醇(bud)和1,5-戊二醇( ped）已通过差示扫描量热法（DSC）、大角X射线散射（LAXS）、小角中子散射进行了研究(SANS)和17 O-NMR弛豫结果表明，二醇(n＝2和4)的水性混合物在低温下容易结晶，而二醇(n＝3和5)的水性混合物在低温下容易结晶。将其作为过冷溶液保存至-100℃。对具有偶数个碳原子的纯二醇晶体结构的X射线衍射研究表明，二醇分子很容易通过氢聚集。这可能是二醇水性混合物容易结晶的原因（n = 2 和 4）。从 25℃ 的水混合物的 SANS 实验中没有观察到明显的小角散射强度，表明乙二醇和水。分子是均匀的……更巧妙地混合在溶液中，例如水和prd-水混合物的^ 17 O-NMR弛豫测量，其中。 H_2^ 17 O富集，表明每种混合物的T_1值随着温度的降低而逐渐降低，这表明在甲醇和乙醇的水混合物的情况下，水分子的旋转运动逐渐受到限制。据报道，在 T_1 值随摩尔分数变化的图中观察到拐点，拐点对应于从水结构到氢键醇链的结构转变，因此，我们得出结论：二醇。二醇-水混合物中的水分子比甲醇-水和乙醇-水混合物中的混合更均匀，即二醇-水混合物中发生剧烈的结构稀缺转变，这是二醇-水混合物可以被混合的原因。目前，利用本项目制备的高压核磁共振池进行了高压下的二醇-水混合物的实验。