Abstract
Here the amphiphilic calix[4]resorcinarenes, which form self-associates in an aqueous solution but do not exhibit surface activity, are described. Aqueous solutions of calix[4]resorcinarenes with different zwitter-ionic groups on the upper rim: carboxybetaine (C5-CB, C11-CB, C12OPh-CB), sulfobetaine (C5-SB, C11-SB), hydroxysulfobetaine (C5-hSB, C11-hSB), - and different hydrophobic substituents on the lower rim (pentyl, undecyl, dodecyloxyphenyl) were studied by fluorimetry, Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR spectroscopy, UV–vis spectroscopy, dynamic light scattering (DLS), and tensiometry. It was found that all macrocycles spontaneously form self-associates in an aqueous solution, but only sulfobetaine and hydroxysulfobetaine calixresorcinarenes with pentyl substituents on the lower rim are surface active. The critical association concentration (CAC) values, which were obtained by different methods, as well as values of averaged hydrodynamic diameter, averaged self-association numbers, solubilizing power, and other parameters of self-association are presented and discussed.
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