Interfacial Rheological and Emulsion Properties of Self-Assembled Cyclodextrin-Oil Inclusion Complexes

To investigate the effect of the molecular size of alkanesandthe cavity size of cyclodextrins (CDs) on the formation of interfacialhost-guest inclusion complexes, the interfacial tension (IFT)of CD (& alpha;-CD, & beta;-CD, & gamma;-CD) solutions against oils(hexadecane, dodecylbenzene) was determined by interfacial dilationalrheology measurements. The results show that the space compatibilitybetween CDs and oil molecules is crucial for the formation of interfacehost-guest inclusion complexes. Hexadecane with a smaller molecularsize can form host-guest inclusion complexes with small cavitiesof & alpha;-CD and & beta;-CD, dodecylbenzene with a larger molecularsize can form interfacial aggregates with the medium-sized cavityof & beta;-CD easily, and the polycyclic aromatic hydrocarbon moleculesin kerosene can form inclusion complexes with the large cavity of & gamma;-CD. The formation of interfacial inclusion complexes leadsto lower IFT values, higher interfacial dilational modulus, nonlinearIFT responses to the interface area oscillating, and skin-like filmsat the oil-water interface. What's more, the phase behaviorof Pickering emulsions formed by CDs with different oils is explored,and the phenomena in alkane-CD emulsions are in line with the resultsin dilatation rheology. The interfacial active host-guest structurein the kerosene-& gamma;-CD system improves the stability of the Pickeringemulsion, which results in smaller emulsion droplets. This uniquespace compatibility characteristic is of great significance for theapplication of CDs in selective host-guest recognition, sensors,enhanced oil recovery, food industries, and local drug delivery.

Automated summary

The effect of molecular size of alkanes and cavity size of cyclodextrins (CDs) on the formation of interfacial host-guest inclusion complexes was investigated. It was found that the space compatibility between CDs and oil molecules is crucial for the formation of these complexes. The formation of interfacial inclusion complexes lead to lower interfacial tension, higher interfacial dilational modulus, non-linear interfacial tension responses, and skin-like films at the oil-water interface.