Department of Chemical and Biomolecular Engineering and Center for Molecular and Engineering Thermodynamics, University of Delaware, 150 Academy St., Newark, Delaware 19716, United States.
Langmuir. 2012 Jul 24;28(29):10703-12. doi: 10.1021/la301876w. Epub 2012 Jul 13.
Dielectric spectroscopy is used to measure the complex permittivity of 200 and 100 nm diameter polystyrene latex suspended in potassium chloride (KCl) solutions over the frequency range 10(4)-10(7) Hz as a function of particle volume fraction (ϕ) and ionic strength. Dilute suspension dielectric spectra are in excellent agreement with electrokinetic theory. A volume fraction dependence of the dielectric increment is observed for low electrolyte concentrations (0.01, 0.05, and 0.1 mM) above ϕ ≈ 0.02. This deviation from the dilute theory occurs at a critical frequency ω* that is a function of volume fraction, particle size, and ionic strength. The dielectric increment of suspensions at the highest salt concentration (1 mM) shows no volume fraction dependence up to ϕ = 0.09. Values of ω* are collapsed onto a master curve that accounts for the length and time scales of ion migration between neighboring particles. The measured conductivity increment is independent of volume fraction and agrees with theory after accounting for added counterions and nonspecific adsorption.
介电谱用于测量直径为 200nm 和 100nm 的聚苯乙烯乳胶悬浮在氯化钾 (KCl) 溶液中的复介电常数，频率范围为 10(4)-10(7)Hz，作为颗粒体积分数 (ϕ) 和离子强度的函数。稀悬浮介电谱与电动理论非常吻合。在低电解质浓度（0.01、0.05 和 0.1mM）下，观察到介电增量随体积分数的依赖性，高于 ϕ ≈ 0.02。这种偏离稀理论的情况发生在一个临界频率 ω*，它是体积分数、颗粒大小和离子强度的函数。在最高盐浓度（1mM）下，悬浮液的介电增量在 ϕ = 0.09 之前没有体积分数依赖性。ω*的值被合并到一个主曲线上，该曲线考虑了相邻颗粒之间离子迁移的长度和时间尺度。测量的电导率增量与体积分数无关，并在考虑添加的抗衡离子和非特异性吸附后与理论相符。
