Effect of valency of cation on micellization behaviour of pluronic mixed micelle F127 and L64

Abstract

In this work the effect of mono, di- and trivalent ions on the micellization and clouding behavior of mixed micellar system has been reported. A mixed pluronic micellar system constituting 0.5 wt%/0.5 wt% of pluronic F127 and L64 has been used for the investigation. The UV and Fluorescence studies were carried out using eosin yellow dye as the probe. Both studies indicate that the mixed micellar system displayed the spectral properties intermediate between the neat pluronic solutions. Also, it was observed that the spectral changes occurring were in the order trivalent > di valent > monovalent cations. The order was not strictly followed in the cloud point observation. With minimum discrepancies the clouding behavior of mixed pluronic followed the order Al3+>Mg2+>K+. Dynamic light scattering studies suggested that the addition of salt changed the particle size of the mixed micelles. This salt effect can be better explained considering the small particle size of cations, such as Na+, Mg2+, and Al3+. There was increase in diameter of mixed micelle from 42.81 nm to 54.99 nm for Na+, to 45.11 nm for Mg2+ and to 46.46 nm for Al3+. The infrared studies also indicated the spectral change of mixed micelle due to salt addition. Different ions affect the dehydration of the PPO core differently. To the best of our knowledge this is the first report of salt and cationic valence effect on mixed micellar system.