Combining Freezing Point Depression and Self-Diffusion Data for Characterizing Aggregation.
Combining Freezing Point Depression and Self-Diffusion Data for Characterizing Aggregation.
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结合凝固点降低和自扩散数据来表征聚集。
DOI：
10.1021/acs.jpcb.8b03456
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
G. Buntkowsky
中科院分区：
文献类型：
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作者：
M. Hoffmann;Sarah Bothe;T. Gutmann;G. Buntkowsky
依数性凝固点下降的评价作为一种手段，用于估计聚（环氧乙烷）醇（C10 E6）的非离子表面活性剂在环己烷中的解决方案的聚集程度。结合额外的测量自扩散系数，它表明，未聚集的C10 E6以及反胶束是显着存在的测量C10 E6浓度（0.048-2.35摩尔kg-1）的整个范围。近0.2摩尔kg-1的形态的变化表示从冰点下降和自扩散系数测量的结果。结果表明，从溶剂和C10 E6自扩散系数的比值得到的平均反胶束半径和聚集数与以前报道的结果一致。然而，不合理的小半径的反胶束，以及为环己烷的斯托克斯-爱因斯坦方程，使用额外的测量溶液粘度的结果进行分析。反胶束和未聚集的C10 E6的浓度从凝固点降低结果使用从自扩散系数的比率获得的聚集数计算。这些浓度表明，反胶束的平均尺寸变小，并且随着温度的升高而数量增加，而未聚集的C10 E6没有增加。
The colligative property freezing point depression is evaluated as a means for estimating the extent of aggregation for solutions of poly(ethylene oxide) alcohol (C10E6) nonionic surfactant in cyclohexane. Combined with additional measurements of self-diffusion coefficients, it is shown that both unaggregated C10E6 as well as reverse micelles are significantly present for the entire range of measured C10E6 concentration (0.048-2.35 mol kg-1). A change in speciation near 0.2 mol kg-1 is indicated by the results from both freezing point depression and self-diffusion coefficient measurements. It is shown that average reverse micelle radii and aggregation numbers obtained from the ratio of solvent and C10E6 self-diffusion coefficients are consistent with prior reported results. However, unreasonably small radii for the reverse micelles as well as for the cyclohexane were obtained from analysis of the results by the Stokes-Einstein equation using additional measured solution viscosities. The concentration of reverse micelles and unaggregated C10E6 was calculated from the freezing point depression results using the aggregation numbers obtained from ratio of self-diffusion coefficients. These concentrations indicate that the reverse micelles become smaller in average size and increase in number with increasing temperature without an increase in unaggregated C10E6.