Matsugami Masaru, Takamuku Toshiyuki, Otomo Toshiya, Yamaguchi Toshio
Department of Functional Molecular Science, The Graduate University for Advanced Studies, Myodaiji, Okazaki 444-8585, Japan.
J Phys Chem B. 2006 Jun 29;110(25):12372-9. doi: 10.1021/jp061456r.
Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire mole fraction range of EG, 0 < or = x(EG) < or = 1, have been clarified by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), and small-angle neutron scattering (SANS) techniques. The DSC curves obtained have shown that the EG-water solutions over the range of EG mole fraction 0.3 < or = x(EG) < or = 0.5 are kept in the supercooling state until approximately 100 K, and those in the range of 0.6 < or = x(EG) < or = 0.8 are vitrified, and those in the ranges of 0 < x(EG) < or = 0.2 and 0.9 < or = x(EG) < 1 are crystallized. The radial distribution function (RDF) for pure EG obtained from the LAXS measurements has suggested that a gauche conformation of an EG molecule is favorable in the liquid. The RDFs for the EG-water solutions have shown that the structure of the binary solutions moderately changes from the inherent structure of EG to the tetrahedral-like structure of water when the water content increases. The SANS intensities for deuterated ethylene glycol (HOCD2CD2OH) (EGd4)-water solutions at x(EG) = 0.4 and 0.6 have not been significantly observed in the temperature range from 298 to 173 K, showing that EG and water molecules are homogeneously mixed. On the other hand, the SANS intensities at x(EG) = 0.2 and 0.9 have been strengthened when the temperature decreases due to crystallization of the solutions. On the basis of all the present results, a relation between thermal properties of EG-water binary solutions and their mixing states clarified by the LAXS and SANS measurements has been discussed at the molecular level.
通过使用差示扫描量热法（DSC）、大角度X射线散射（LAXS）和小角度中子散射（SANS）技术，已阐明了乙二醇（EG）-水二元溶液在EG的整个摩尔分数范围（0≤x(EG)≤1）内的热性质和混合状态。所获得的DSC曲线表明，EG摩尔分数在0.3≤x(EG)≤0.5范围内的EG-水溶液在大约100 K之前一直处于过冷状态，在0.6≤x(EG)≤0.8范围内的溶液会玻璃化，而在0＜x(EG)≤0.2和0.9≤x(EG)＜1范围内的溶液会结晶。从LAXS测量中获得的纯EG的径向分布函数（RDF）表明，EG分子的gauche构象在液体中是有利的。EG-水溶液的RDF表明，当含水量增加时，二元溶液的结构会从EG的固有结构适度地转变为类似水的四面体结构。在298至173 K的温度范围内，未显著观察到x(EG)=0.4和0.6时氘代乙二醇（HOCD₂CD₂OH）（EGd₄）-水溶液的SANS强度，表示EG和水分子均匀混合。另一方面，当温度因溶液结晶而降低时，x(EG)=0.2和0.9时的SANS强度会增强。基于所有目前的结果，已在分子水平上讨论了EG-水二元溶液的热性质与其通过LAXS和SANS测量所阐明的混合状态之间的关系。
