In order to reveal the influence of the guest molecular structure, the interactions between 4-sulfonatocalix[n]arene (SCXn) cavitands (n = 4 or 6) and two series of quinolinium derivatives were studied in neutral aqueous solutions at 298 K. For this, the long alkyl chain of the quinoliniums was attached either to the heterocyclic nitrogen (CmC1OQ+ m = 10, 12, or 14) or to the oxygen located in position 6 of the aromatic system (C1CmOQ+ m = 8, 10, or 12). All the quinolinium derivatives self-assembled with SCXn into nanoparticles (NP), whose size, zeta potential and composition were determined over a large molar mixing ratio range. Isothermal titration calorimetry showed that host-guest binding assisted the formation of negatively charged NPs in exothermic processes. The enthalpy gain in these associations significantly increased with the lengthening of the 1-alkyl group but was insensitive to the size of the SCXn macrocycle. The morphology of NPs was studied by cryo-TEM method. CmC1OQ+ organization with SCXn led to spherical NPs without regular inner structure. In contrast, C1CmOQ+-SCXn nanoaggregates usually had various shapes and the original morphologies exhibited lamellar domains with ~3 nm layer thickness. The different orientation of CmC1OQ+ and C1CmOQ+ in the cavitand was proposed to rationalize the morphological alterations
