水/乙醇/正辛醇无表面活性剂微乳液的介电弛豫谱

doi:10.19894/j.issn.1000-0518.200345

摘要/Abstract

摘要： 无表面活性剂微乳液近年来受到人们极大关注,但人们对该类微乳液体系的了解还不够深入,在许多基础问题上仍存在较大争议,因此十分有必要利用不同的技术手段对该类体系开展研究。介电谱是表征微乳液体系的有效方法之一,但在无表面活性剂微乳液体系中的应用还鲜有报道。根据水/乙醇/正辛醇所组成的三元体系相图,选取了3条路径配制了不同相组成的微乳液样品,进而在40 Hz～110 MHz频率范围内测量了这些样品的介电谱。发现在1～10 kHz频率范围内出现了明显的介电弛豫现象,利用Cole-Cole公式对该介电弛豫行为进行了拟合解析,从而准确获取了表征该介电弛豫特征的介电参数。通过分析介电参数对微乳液样品的相组成的依存性,发现介电参数能够较为准确地区分该微乳液体系的不同微观相区,其结果与文献报道基本一致。对不同微观相区内介电参数随体系相组成的变化规律进行了分析和讨论,据此提出了不同相区内该弛豫可能的微观弛豫机制。结果表明,不同的微观相区中该弛豫的微观机制不同:在分子溶液相区,该弛豫来自于电极上双电层内离子的迁移或氢键形成的网络中离子的迁移;在水包油及双连续相区,该弛豫来自于水相中离子的跳跃迁移;而在油包水相区,该弛豫来自于分散水滴在油相中的转动极化。

关键词: 介电谱, 无表面活性剂微乳液, 介电弛豫, 弛豫时间, 弛豫强度

Abstract: Surfactant-free microemulsions receive intense concern recently, but the understanding on this type of microemulsion is still far from enough, and controversies still remain on many fundamental issues; accordingly it is very necessary to carry out investigations on this type of microemulsion by means of various techniques and approaches. Dielectric spectroscopy is an effective method for characterization of microemulsions, but the application of dielectric spectroscopy on surfactant-free microemulsions is rarely reported. In this study, in line with the phase diagram of water/ethanol/1-octanol ternary system, three paths were selected and used for the preparation of microemulsion samples with different phase compositions, and the dielectric spectra of these samples were measured in the frequency range of 40 Hz~110 MHz. An apparent dielectric relaxation phenomenon was observed for all samples in the frequency range of 1～10 kHz, which was analyzed in line with the Cole-Cole equation, and dielectric parameters representing the characteristics of the relaxation were accurately determined. Through analyzing the dependences of these dielectric parameters on the phase composition of the samples, it is found that dielectric parameters can be used to differentiate different microscopic phase regions, with a result basically consistent with what is reported in literatures. The variation of the dielectric parameters on the phase composition was discussed, based on which the possible relaxation mechanism of the observed relaxation in each phase region was proposed. It is suggested that the relaxation mechanisms at different phase regions are different: in the molecular solution phase region, the observed relaxation originates from transportation of ions within the double layer adjacent to the electrode or diffusion of ions in a network of hydrogen bond; in the oil-in-water and bicontinuous phase regions, this relaxation is due to hopping transportation of ions in the water phase; and in the water-in-oil phase region, this relaxation is ascribed to the rotational polarization of water droplets in the oil phase.

Key words: Dielectric spectroscopy, Surfactant-free microemulsion, Dielectric relaxation, Relaxation time, Relaxation intensity

中图分类号:

O648

刘灿利, KHAN Asadullah Muhammad, 陈震. 水/乙醇/正辛醇无表面活性剂微乳液的介电弛豫谱[J]. 应用化学, 2021, 38(7): 836-846.

LIU Can-Li, KHAN Asadullah Muhammad, CHEN Zhen. Dielectric Relaxation on Surfactant-Free Microemulsion Composed of Water/Ethanol/1-Octanol[J]. Chinese Journal of Applied Chemistry, 2021, 38(7): 836-846.

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