Complexes between β-cyclodextrin and aliphatic guests as new noncovalent amphiphiles:: Formation and physicochemical studies

The aim of this work was to develop new sugar nonionic surfactants from raw materials of plant origin. These nonionic surfactants are based on the noncovalent association between cyclodextrins (CDs) and fatty alcohols or fatty acids. We describe here (i) the preparation of various complexes between beta-cyclodextrin (beta-CD) and fatty alcohols or fatty acids, (ii) the evaluation of the surfactive properties of the complexes, and (iii) the structure of one of them which presents interesting surfactive properties. Among the prepared complexes, the beta-CD/alcohol complexes present high surface tension efficiencies compared with beta-CD/acid complexes. The surfactive properties of the beta-CD/alcohol complexes are influenced by the length of the hydrocarbon chain and reach an excellent efficiency for guests having 10-12 carbon atoms. For the complex between beta-cyclodextrin and undec-10-en-1-ol, the inclusion mode in aqueous solution was described by nuclear magnetic resonance techniques. The results showed a 1:1 stoichiometry and a dynamic process exchanging the two possible orientations of the guest relative to the beta-CD.