Effects of head group and counter-ion variation in cationic surfactants on the microstructures of EO-PO block copolymer micelles

Abstract

This study reports the effect of several cationic surfactants namely C16TABr,C16TPPBr, C16TBPBr, C16PyBr, C16TACl and C16TATs, each with 16C long alkyl side chain but different counterions and head groups on the micellar behavior of an ethylene oxide-propylene oxide (EO-PO) linear triblock copolymer, Pluronic® 103 from cloud point (CP), dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. The solubilizing capacity of the mixed system was also checked for a poorly water soluble drug quercetin (QN). We show that cationic surfactants in the aqueous copolymeric system enhanced the surface charge density on P103 micelles. Eventually, increase in repulsion leads to micellar break down. This was manifested as reduction in micelle size and upshifted CP. However, the mixed system offered significant increase in solubilization of QN. The results from the present study may be helpful in developing a basic understanding to choose appropriate cationic surfactants for the desired applications and to attain preferred micellar dimensions and morphology.