Exploring the charged nature of supramolecular micelles based on p-sulfonatocalix[6]arene and dodecyltrimethylammonium bromide

Abstract

The aggregation of supramolecular amphiphiles formed from hexamethylated p-sulfonatocalix[6]arene (SC6HM) and dodecyltrimethylammonium bromide (C12TAB) was studied by capillary electrophoresis experiments and by kinetic probes. The hydrolysis of 4-methoxybenzenesulfonyl chloride (MBSC) was used to investigate the micropolarity of the micellar aggregates and their ability to solubilize and stabilize labile organic compounds against hydrolysis. Further insights were obtained using a more sophisticated kinetic probe: the basic hydrolysis of p-nitrophenylvalerate (NPV). This probe provides information on the ionic composition of the micellar interface and on the potential of the aggregates to be used as nanoreactors. The results obtained revealed that the charge of the micellar aggregates can be tuned from anionic to cationic through the adjustment of the C12TAB : SC6HM molar ratio and confirmed that these micelles have good solubilization properties. On the other hand, the kinetics of the p-nitrophenylvalerate basic hydrolysis suggest that, in the concentration range comprised between the first and second CMCs, Br(-) anions do not take part in the micellar structure.

Assembling features of calixarene-based amphiphiles and supra-amphiphiles

“…Basilio and coworkers measured the hydrophobicity of dodecyltrimethylammonium bromide (G10) assembly by measuring the hydrolysis rate of two kinetic probes. 314 Hydrolysis rates at different surfactant concentrations were plotted and fitted, from which the binding constant of the kinetic probe between the micelles and the bulk water (K S m ) was obtained. The K S m value of G10 in the absence of 458 is smaller than that in the presence of 458, which means the addition of 458 leads to stronger hydrophobicity of aggregates.…”

p-Sulfonatocalix[6]arene-dodecyltrimethylammonium Supramolecular Amphiphilic System: Relationship between Calixarene and Micelle Concentration

“…However, these topics remain largely unexplored. Exceptions include some work from our group and other groups concerning systematic studies on the induced aggregation of surfactants and dyes. ,− The SC n -induced aggregation shows some parallelism with similar effects displayed by polyelectrolytes in the presence of oppositely charged amphiphilic compounds. As recognized by Guo and co-workers, the main differences between these two classes of compounds arise from the fact that SC n can form strong 1:1 host–guest complexes that predominate when the calixarene is present in excess, therefore dissociating the aggregates .…”

“…In previous works, the induced aggregation of cationic surfactant do­decyl­tri­methyl­ammonium bromide (C 12 TAB) by hexa­methyl­ated p -sulf­onato­calix­[6]­arene (SC6HM) was investigated in detail (Scheme ). ,,, Diffusion-ordered NMR spectroscopy is a powerful technique for characterizing the complex aggregation process (Figure ). , For concentrations of surfactant below ca.…”

Supraamphiphilic Systems Based on Metallosurfactant and Calix[4]resorcinol: Self-Assembly and Drug Delivery Potential

“…Moreover, calixarenes are capable of forming complexes with various ions and small organic molecules, which can enter the aromatic cavity of the calixarene framework. − The guest molecules can also be bonded by calixarene substituents located outside the macrocyclic cavity. Sulfonated calix[4]­arenes typically form supraamphiphiles with cationic surfactant molecules due to electrostatic interactions. ,,,− The complexation between the surfactant and the macrocycle in this case leads to a decrease in the critical aggregation concentration compared of the individual components. The joint aggregates of calixarene and surfactant are vesicular in nature and can be used as drug nanocontainers.…”