Frequency-Dependent Solvent Impedance and Colloid Microelectrophoresis Measurements in Partially Polar Solvents

• Published in: Langmuir Vol. 33; no. 19; pp. 4781 - 4788
• Main Authors: Hayden, Edward, Aljabal, Zena, Yethiraj, Anand
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16.05.2017
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.7b00816

We carry out frequency-dependent solvent impedance measurements and alternating current (ac) colloid microelectrophoresis experiments in partially polar solvents in the low-frequency regime (0.25 Hz ≤ f ≤ 10 Hz). Solvent electrode polarization effects are quantified first in partially polar solvent mixtures containing bromocyclohexane (CHB). We find that the polarization capacitance from electrode polarization exhibits a clear power law behavior C p = C p0 f –m with power law exponent m = 0.25 ± 0.04. Once we account for electrode polarization effects, we are able to obtain quantitative mobilities in the low-frequency regime from our ac microelectrophoresis measurements; for these measurements, we use poly­(methyl methacrylate colloids that are gravitationally confined to a plane while suspended in a low-polar solvent mixture of cis–trans decahydronapthalene and CHB. We find that the dimensionless electrophoretic mobility is constant, consistent with expectations for frequencies below the ion-diffusion frequency, and has a value E = 1.6 ± 0.4.