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 1H 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 γ for 12-s-12 remains almost constant until 12-s-12 content reaches C1, then decreases sharply until C2, 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 Ca, followed by a short plateau until Cb, and then, the surface tension increases sharply until Cc, 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.