Dielectric Relaxation on Surfactant-Free Microemulsion Composed of Water/Ethanol/1-Octanol

doi:10.19894/j.issn.1000-0518.200345

Chinese Journal of Applied Chemistry ›› 2021, Vol. 38 ›› Issue (7): 836-846.DOI: 10.19894/j.issn.1000-0518.200345

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Dielectric Relaxation on Surfactant-Free Microemulsion Composed of Water/Ethanol/1-Octanol

LIU Can-Li, KHAN Asadullah Muhammad, CHEN Zhen^*

Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei 230036, China

Received:2020-11-18 Accepted:2021-02-24 Published:2021-07-01 Online:2021-09-01
About author:National Natural Science Foundation of China (No.21673002)

Abstract

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

CLC Number:

O648

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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Dielectric Relaxation on Surfactant-Free Microemulsion Composed of Water/Ethanol/1-Octanol

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