PARTITIONING BEHAVIOR AND THERMODYNAMIC MODEL FOR STYRENE O/W MICROEMULSIONS

The effect of surfactant, co-surfactant, and salt content on the component partitioning behavior in oil-in-water microemulsions, consisting of styrene, water, sodium dodecyl sulfate (SDS), and 1-pentanol, was explored using three techniques: a diffusion method, partitioning measurements, and 13C NMR chemical shielding. The results showed that more than 60% of the 1-pentanol partitions into the interface with most of the styrene residing in the oil phase. The partitioning of styrene and 1-pentanol in the interface increases with increasing 1-pentanol content in the microemulsion. The aggregation number of SDS associated with each microemulsion droplet decreases with increasing 1-pentanol and remains constant with increasing SDS in the system. The increased partitioning of 1-pentanol in the interface allows more styrene to be solubilized in the hydrophobic region created by the SDS. The size of the microemulsion droplets decreases with increasing 1-pentanol or SDS in the system. The addition of salt did not change the phase compositions in the styrene microemulsions. A thermodynamic model was developed to describe the compositions of each phase in a styrene microemulsion. © 1992.