Colloids and Surfaces A: Physicochem. Eng. Aspects 292 (2007) 42–50 Dielectric relaxation spectroscopy of macroporous IER beads suspensions dispersed in primary alcohols and water–ethanol mixtures Zhen Chen, Kong-Shuang Zhao ∗ College of Chemistry, Beijing Normal University, Beijing 100875, China Received 23 March 2006; received in revised form 1 June 2006; accepted 5 June 2006 Available online 10 June 2006 Abstract Dielectric measurements were first carried out on suspensions of ion-exchange resin beads dispersed in primary alcohols and water–ethanol mixtures in the frequency range 40 Hz–110 MHz. Due to the large bead radius, only Maxwell–Wagner (M–W) dielectric relaxations were observed. Regular dielectric behaviors were observed and phase parameters concerning constituent phases’ properties were determined through dielectric analysis, which revealed that the properties and the dispersing state of the bead are strongly dependent on the properties of dispersion medium. It is also found that dry beads cannot be completely soaked by alcohols with long aliphatic chain, and that suspension in water-rich mixture has similar dielectric behavior as in pure water due to the mixture’s molecular construction. Then the dielectric behaviors of the following suspensions were measured as a function of time: suspensions of beads that have been equilibrated with water/ethanol redispersed in ethanol/water. The dielectric behaviors showed remarkable time dependency, characterized by distinct transitions on the curves of time dependent relaxation parameters. Based on the above understandings, the time dependent dielectric behaviors were analyzed in detail. It is showed that the time dependency directly reflected such processes as ion diffusion, solvent diffusion and solvent uptake that the systems undergo. © 2006 Elsevier B.V. All rights reserved. Keywords: Dielectric relaxation spectroscopy; Ion-exchange resin beads; Water–ethanol mixture; Hanai’s equation; Concentrated suspension 1. Introduction Maxwell–Wagner (M–W) polarization [1–3] and counterion polarization (concentration polarization) [4–6] are two most typ- ical polarization mechanisms for particle suspensions subject to an oscillating field. The former is owing to the famous M–W effect [1,2] extended by O’Konski [7] by introducing the con- cept of surface conductivity, typically occurring at frequency of the order of megahertz. While the latter arises from the diffu- sion of ions in the bulk solution adjoining the electric double layer (EDL) according to the recent understandings [6,8–12], which may occur at frequency down to a few hertz or up to several kilohertz resting with the size of the dispersed parti- cle. Due to the development of theoretical [8–12] and numerical [13–16] treatment in the last 40 years, dielectric relaxation spec- troscopy (DRS) based on these mechanisms has become one of the most practical methods used for the characterization of ∗ Corresponding author. Tel.: +86 10 58808283. E-mail address: zhaoks@bnu.edu.cn (K.-S. Zhao). particle suspensions, offering valuable information about the electrical properties of particle, dispersion medium and their interfaces [17–22]. Despite a number of successful applications, experimental investigations still lag seriously behind theoretical studies. Furthermore, these theories cannot be applied to most actual systems due to their theoretical restrictions, and actual systems usually involve more complicated polarization processes, for example porous materials [23,24]. This situation demands that more experimental investigations on actual systems should be carried out. On the other hand, DRS has some unique advantages: (1) it is rather sensitive to the properties of con- stituent phases and interfaces, which guarantees that even tiny changes of the system under measurement can be identified; (2) it is non-invasive, making in situ dielectric measurement on the systems in their working state to be possible; and (3) dielectric measurement can be completed very quickly so that non-equilibrium systems can be instantaneously monitored. Therefore, even without theoretical schemes it is still possible to obtain valuable information about actual systems by means of DRS. 0927-7757/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2006.06.001