Investigating the Effect of Penetrant Identity on Micelle Formation and Release Time from Organogels.

Previous research has demonstrated that sodium dioctyl sulfosuccinate (AOT) forms a reverse micelle in mineral oil and diffuses as nanocarrier molecules in an organogels whilst oleic acid releases as single molecules, which is fundamental to our understanding of nanostructure diffusion relationships and applications such as drug delivery. These observations have shown promise for further exploration on the potential for other organic molecules to form reverse micelles in gels. The current study investigates whether two surfactants, Solsperse 3000 and Solsperse 9000, would form reverse micelles, and how much time it would take for the full release in different concentrations of styrene ethylene butylene styrene (SEBS) polymer (10wt% - 40wt%) using the Fourier transform infrared spectroscopy-based method for tracking diffusion. The average diffusivities of Solsperse 3000 and 9000 were measured to be 9.87E-09 cm²/s and 9.96E-09 cm²/s respectively, over a full release time of approximately 300 hours which is similar to the release time of AOT but is higher than the AOT calculated value of 4.61E-09 cm²/s by a factor of two. Additionally, the diffusivities of the Solsperse molecules were compared to oleic acid’s 6.21E-08 cm²/s which showed a larger difference by a factor of approximately ten. Our results show that suggest that the Solsperse 3000 and Solsperse 9000 were similar molecules as confirmed by the H-NMR. Solsperse 3000 and 9000 did not form reverse micelles as confirmed of the structural information from dynamic light scattering on the size of the molecule but rather released as a singular molecule. While oleic acid also releases as a single molecule it wasn’t found to be affected by the concentration of the polymer whereas Solsperse 3000 and 9000 were. This yielded the additional conclusion that it takes a single releasing molecule of significant size to be affected by changing polymer concentration.