Dynamical Behavior of Probe Molecules and Dominant Role of Cosurfactants in Reverse Micelles

Abstract

Reverse micelles (RM) are nanopools of water surrounded by surfactant molecules in a non-polar solvent. Our studies investigated properties of RM probe molecules in the interfacial boundary between water and non-polar solvents. Reichardt’s dye, a probe molecule, was used to uncover properties of RM. UV/vis spectroscopy of Reichardt’s dye reveals information about polarity and the dye’s approximate residential location and also helps confirm molecular orbital energy diagram. We discovered an interesting phenomenon with Reichardt’s dye in RM. Surprisingly, the UV/vis spectrum of Reicahrdt’s dye in CTAB RM with octanol as a cosurfactant exhibits decreasing absorbance and a blue shift. Reichardt’s dye in solely octanol shows an irreversible color change and similar UV/vis spectrum. Consequently, we conclude that Reichardt’s dye resides near the interfacial layer/solvent boundary. Other cosurfactants do not result in the time dependent behavior suggesting a more dynamic interaction between octanol and Reichardt’s dye.