Structure and dynamics of hexafluoroisopropanol-water mixtures by x-ray diffraction, small-angle neutron scattering, NMR spectroscopy, and mass spectrometry
Structure and dynamics of hexafluoroisopropanol-water mixtures by x-ray diffraction, small-angle neutron scattering, NMR spectroscopy, and mass spectrometry
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DOI：
10.1063/1.1602070
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发表时间：
2003-09-22
影响因子：
4.4
通讯作者：
Nishi, N
中科院分区：
文献类型：
--
作者：
Yoshida, K;Yamaguchi, T;Nishi, N
采用大角x射线散射（LAXS）、小角中子散射（SANS）、F-19-、C-13-和O-17-NMR化学位移、O-17-NMR弛豫和质谱等方法，研究了1,1,3,3,3-六氟-2-丙醇（HFIP）水溶液混合物在HFIP摩尔分数（x(HFIP)）范围内的结构和动力学性质。LAXS数据表明，溶剂团簇在x（HFIP）近似于0.1时发生结构转变，从x（HFIP）小于等于0.1时的水的四面体氢键网络向在x（HFIP）大于等于0.15范围内随着HFIP浓度的增加逐渐形成整齐的HFIP结构。SANS数据的Ornstein-Zernike图显示出一种介观结构特征，即浓度波动在x（HFIP）接近0.06时最大，相关长度接近9埃，即聚类和微观非均质性最大。HFIP的CF3和CH基团对x（HFIP）的F-19和C-13的化学位移在x（HFIP）处出现了一个类似于0.08的拐点，这表明HFIP分子的环境由于HFIP簇的结构转变而发生了变化。水的O-17弛豫数据表明，加入HFIP后，水分子的旋转运动在x（HFIP）接近0.1的范围内迅速减慢，在接近0.1的范围内适度减慢
The structure and dynamic properties of aqueous mixtures of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) have been investigated over the whole range of HFIP mole fraction (x(HFIP)) by large-angle x-ray scattering (LAXS), small-angle reutron scattering (SANS), F-19-, C-13-, and O-17-NMR chemical shifts, O-17-NMR relaxation, and mass spectrometry. The LAXS data have shown that structural transition of solvent clusters takes place at x(HFIP)similar to0.1 from the tetrahedral-like hydrogen bonded network of water at x(HFIP)less than or equal tosimilar to0.1 to the structure of neat HFIP gradually formed with increasing HFIP concentration in the range of x(HFIP)greater than or equal to0.15. The Ornstein-Zernike plots of the SANS data have revealed a mesoscopic structural feature that the concentration fluctuations become largest at x(HFIP)similar to0.06 with a correlation length of similar to9 Angstrom, i.e., maximum in clustering and microhetrogeneities. The F-19 and C-13 chemical shifts of both CF3 and CH groups of HFIP against x(HFIP) have shown an inflection point at x(HFIP)similar to0.08, implying that the environment of HFIP molecules changes due to the structural transition of HFIP clusters. The O-17 relaxation data of water have shown that the rotational motion of water molecules is retarded rapidly upon addition of HFIP into water up to x(HFIP)similar to0.1, moderately in the range of similar to0.1