Cosolvent Effects on the Spontaneous Formation of Nanorod Vesicles in Catanionic Mixtures in the Rich Cationic Region

Abstract

The aggregation behavior of cation-rich catanionic mixtures of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) was investigated in water-ethylene glycol (EG) solutions by performing surface tension, electrical conductivity, pulsed field gradient nuclear magnetic resonance, transmission electron microscopy, and cyclic voltammetry measurements. Different physicochemical properties such as the critical micelle concentration, degree of counterion dissociation (α), interfacial properties, aggregation numbers, morphology of aggregates, and interparticle interaction parameters were determined. Cosolvent effects on the interactions between the two surfactants CTAB and SDS were analyzed on the basis of regular solution theory, both for mixed monolayers at the air/liquid interface (β(δ)) and for mixed micelles. It was shown that an excess of cationic surfactant resulted in the formation of nonspherical vesicles. These were predominantly nanorod vesicles in water-EG mixed solvents. The interparticle interactions were assessed in terms of cosolvent effects on the micellar surface charge density, the sphere-to-rod morphology change, and the phase transition from vesicles to mixed micelles. Moreover, the variation of the repulsive electrostatic potential energy between two pairs of aggregates was investigated for two modes of nanostructural transition, namely the transition between spherical and rod-like micelles and the transition between rod-like micelles and nanorod vesicles.

Bile salt-surface active ionic liquid mixtures: mixed micellization and solubilization of phenothiazine

“…This change in behavior of oppositely charged surfactant mixtures at equimolarity has been exemplified earlier [34][35][36][37][38]. The cmc values of the various NaC/NaDC + C 12 mimBr aqueous mixtures are found to be quite lower than their pure counterparts.This is highly expected as the mixtures involve oppositely charged amphiphiles (bile salts being negatively and SAIL being positively charged) and hence the interactions in the mixed micelles would beattractive because of the enhanced newer electrostatic and hydrophobic forces.…”

Effect of surfactant head group on micellization and morphological transitions in drug-Surfactant catanionic mixture: A multi-technique approach

“…The increasing mole fraction of TC into SLS and SDBS reduces the cmc than pure amphiphiles due to presence of strong electrostatic interactions among oppositely charged head groups as well as hydrophobic interactions between tails. The cmc values of TC + SLS/SDBS mixtures continues to decrease with increasing mole fraction of TC but starts to increase in cationic rich region, which have been commonly observed in catanionic mixtures [29][30][31]. The somewhat different behavior have been observed at αTC = 0.9 in TC + SDBS mixtures, where the cmc value again decreases which can be ascribed to vesicle formation (discussed later) guided by strong binding forces among oppositely charged molecules.…”

Synthesis of RAFT‐Mediated Amphiphilic Graft Copolymeric Micelle Using Dextran and Poly (Oleic Acid) toward Oral Delivery of Nifedipine

“…(b)], the spherical like morphology was changed to rod shaped. This variation of surface nature is probably because of the structural change above the CMC of copolymer, which facilitates the change in surface morphology from spherical to nonspherical (rod shaped).…”