Adsorption behaviors and emission properties of p-sulfonatocalixarene/ammonium-based surfactant systems: A comparison between the effects of gemini surfactant and its corresponding monomeric surfactant

So far, the research on calixarene/surfactant systems has been mainly focused on their aggregation characteristics due to their potential applications as stimuli-responsive systems, while the reports about their absorption behavior and spectroscopic properties have been limited. Understanding basic properties of supra-amphiphilic molecules is of great significance to improve their application performance and expand their application potential. In the present study, the interactions of p-sulfonatocalix[n]arenes (SC[n], n = 4, 6 and 8) with the cationic surfactants (including dodecyltrimethyl ammonium bromide (DTAB), pentamethylene-1,5-bis (dimethyldodecyl ammonium bromide) (12-5-12), and octamethylene-1,8-bis(dimethyldodecyl ammonium bromide (12-8-12)) were studied by measuring surface tension, fluorescence spectra and H-1 NMR spectra. It was found that SC[n] changed the absorption behaviors of 12-s-12 (s = 5 and 8) and DTAB at air/water surface in different ways. In the presence of SC[n], the value of gamma for 12-s-12 remains almost constant until 12-s-12 content reaches C-1, then decreases sharply until C-2, followed by a slow decrease up to the CMC. The surface tension of DTAB/SC[n] solution begins to decrease at a very low concentration of DTAB until C-a, followed by a short plateau until C-b, and then, the surface tension increases sharply until C-c, after which, the surface tension curve gradually overlaps with that of single DTAB solution. Meanwhile, the binding of SC[n] with these surfactants makes SC[n] emit fluorescence, and the quantum yields for SC[n]/12-s-12 systems are higher than those for SC[n]/DTAB systems. Supra-amphiphiles have been expected as smart materials. This study may provide meaningful information for application of calixarene-based supra-amphiphiles.