Colloids in low-polar solvent under influence of an electric field

Abstract

In this thesis we discuss the behaviour of suspended bullet-shaped rods in electric fields. Confocal microscopy is used to observe rodlike silica particles under the influence of a 1 MHz alternating electric field. Particle tracking software allows us to obtain the angle between the rods and the direction of the electric field, from which we calculate the two dimensional nematic order parameter. The results are compared with a theoretical model assuming ellipsoidal particles in electric fields. This model agrees with our experimental results. For high enough electric fields, the rodlike particles align with the electric field. We also wish to know the zeta potential and charge on the rods. Since no theoretical model exists relating macroscopic properties to these quantities we use spherical silica particles as an approximation. We observe suspended spherical silica particles under influence of a non-alternating electric field at two different concentrations using confocal microscopy and obtain their speeds using particle tracking software. Their electrophoretic mobilities are calculated while considering the effects of gravity and flows of the solvent. From the mobilities the zeta potential and particle charge are calculated, resulting in between 40 to 521 unit charges per sphere and zeta potentials ranging from 11.2 mV to 145 mV.