Eliminating Magnetic Forces from the Surface Tension Measurement of Magnetic Surfactants

摘要

Surfactants have many applications due to their ability to reduce the surface tension between two phases. Magnetic surfactants, a relatively new form of surfactants, offer the possibility of further controlling a surfactant system by using an external magnetic field to induce alignment on the molecular level. One method of studying a magnetic field’s effect on the magnetic surfactant system involves analyzing the change in surface tension at varied solution concentrations both in and outside a magnetic field. The pendent drop method uses the downward gravitational force on a droplet suspended from a needle to find the surface tension based on the drop’s shape. Previous results with the magnetic surfactant [C16TA]2CoCl2Br2 show an overall decrease in the surface tension of the solution when suspended over a permanent magnet. While this change could point to the surfactant’s molecular realignment, permanent magnets produce a magnetic field gradient that could directionally pull the surfactant towards the magnet, potentially acting as a downward force not accounted for in the pendent drop correlations that only use gravity. This scenario would also result in a calculated surface tension change. We continued the initial investigation by replicating it with the magnetic surfactant C16TAFeCl3Br as well as analyzing its surface tension inside a parallel magnetic field to remove the gradient and eliminate the opportunity for varied effective gravity on the drop. The obtained results match the trend of a surface tension reduction when inside a magnetic field which suggests the idea of induced alignment of the surfactant; however, the data only supports this clearly when using the higher magnetic field levels.