Cucurbituril and α- and β-cyclodextrins as ligands for the complexation of nonionic surfactants and polyethyleneglycols in aqueous solutions

The complexation of nonionic surfactants and polyethylene glycols by the ligands cucurbituril, alpha- and beta-cyclodextrin was studied in aqueous solution. All the examined guest molecules form complexes with these ligands. Calorimetric titrations were performed to determine directly the stability constants and reaction enthalpies. The presence of an aromatic part in nonionic surfactants leads to more stable complexes with beta-cyclodextrin than with the other ligands. If the surfactants contain no benzene group, the interactions with alpha-cyclodextrin are stronger compared to other ligands. The chain length of the polyethylene glycols has only an influence upon the values of the reaction enthalpy in the case of alpha-cyclodextrin.