Comparative studies on molecular induced aggregation of hepta-imidazoliumyl-β-cyclodextrin towards anionic surfactants

A β-cyclodextrin derivative bearing seven cationic arms and its singly charged analogue, i.e., per-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin (3) and mono-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin (4) were synthesized and fully characterized. Their induced aggregation behaviours towards two anionic surfactant, that is, sodium dodecyl sulfonate (SDS) and dioctyl sodium sulfosuccinate (Aerosol OT, AOT), were investigated by UV–vis, NMR, Zeta-potential, dynamic light scattering (DLS), and transmission electron microscopy. The results revealed that host 3 can induce the molecular aggregation of anionic surfactant at concentration far lower than its original CAC, leading to the larger diameter, the narrower size distribution and the higher thermal stability of the induced aggregate towards the anionic surfactant possessing more hydrophobic tails.