Yılmaz Topuzlu Ezgi, Okur Halil I, Ulgut Burak, Dag Ömer
Department of Chemistry, Bilkent University, 06800 Ankara, Turkey.
UNAM-National Nanotechnology Research Center and Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey.
Langmuir. 2021 Dec 14;37(49):14443-14453. doi: 10.1021/acs.langmuir.1c02411. Epub 2021 Dec 3.
The lyotropic liquid crystalline (LLC) mesophase forms upon evaporation of water from aqueous solutions of LiX salts (X is Cl, Br, NO, or SCN) and a surfactant [CH(OCHCH)OH, abbreviated as CE]. The LiX/CE/HO aqueous solutions have been monitored (during evaporation of their excess water to obtain stable LLC mesophases) by gravimetric, spectroscopic, and conductivity measurements to elucidate the role of water in these mesophases. The water/salt molar ratio in stable mesophases changes from 1.5 to 8.0, depending on the counteranion of the salt and the ambient humidity of the laboratory. The LiX/CE/HO LLC mesophases lose water at lower humidity levels and absorb water at higher humidity levels. The LiCl-containing mesophase holds as few as four structural water molecules per LiCl, whereas the LiNO mesophase holds 1.5 waters per salt (least among those assessed). This ratio strongly depends on the atmospheric humidity level; the water/LiX mole ratio increases by 0.08 ± 0.01 HO in the LLC mesophases per percent humidity unit. Surprisingly, the LLC mesophases are stable (no salt leaching) in broad humidity (10-85%) and salt/surfactant mole ratio (2-10 LiX/CE) ranges. Attenuated total reflectance Fourier transform infrared spectroscopic data show that the water molecules in the mesophase interact with salt species more strongly in the LiCl mesophase and more weakly in the case of the nitrate ion, which is evident by the shift of the O-H stretching band of water. The O-H stretching peak position in the mesophases decreases in the order ν > ν > ν > ν and accords well with the HO/LiX mole ratio. The conductivity of the LLC mesophase also responds to the amount of water as well as the nature of the counteranion (X). The conductivity decreases in the order σ > σ > σ > σ at low salt mole ratios and in the order σ > σ > σ > σ at higher ratios due to structural changes in the mesophase.
当LiX盐（X为Cl、Br、NO或SCN）与表面活性剂[CH(OCHCH)OH，简称为CE]的水溶液中的水蒸发时，会形成溶致液晶（LLC）中间相。通过重量法、光谱法和电导率测量对LiX/CE/H₂O水溶液（在蒸发其过量水以获得稳定的LLC中间相的过程中）进行监测，以阐明水在这些中间相中的作用。稳定中间相中的水/盐摩尔比从1.5变化到8.0，这取决于盐的抗衡阴离子和实验室的环境湿度。LiX/CE/H₂O LLC中间相在较低湿度水平下失水，在较高湿度水平下吸水。含LiCl的中间相每个LiCl仅含有四个结构水分子，而LiNO₃中间相每个盐含有1.5个水分子（在所评估的中间相中最少）。该比例强烈依赖于大气湿度水平；LLC中间相中每湿度单位百分比，水/LiX摩尔比增加0.08±0.01 H₂O。令人惊讶的是，LLC中间相在较宽的湿度范围（10 - 85%）和盐/表面活性剂摩尔比范围（2 - 10 LiX/CE）内是稳定的（无盐浸出）。衰减全反射傅里叶变换红外光谱数据表明，中间相中的水分子与盐物种的相互作用在LiCl中间相中更强，而在硝酸根离子的情况下较弱，这通过水的O - H伸缩带的位移得以体现。中间相中O - H伸缩峰位置按ν₁＞ν₂＞ν₃＞ν₄的顺序降低，并且与H₂O/LiX摩尔比非常吻合。LLC中间相的电导率也对水量以及抗衡阴离子（X）的性质作出响应。在低盐摩尔比下，电导率按σ₁＞σ₂＞σ₃＞σ₄的顺序降低，而在较高比例下，由于中间相的结构变化，电导率按σ₂＞σ₁＞σ₃＞σ₄的顺序降低。
