Interfacial behavior of cyclodextrins at the oil-water interface of Pickering emulsion

An oil-in-water (O/W) Pickering emulsion stabilized by cyclodextrins (CDs), including alpha-, 8-, gamma-CD, and the hydroxypropyl (HP) derivatives, was prepared by high-speed homogenization. The interfacial behavior of CDs was studied by the contact angle, surface tension, interface tension, and adsorption kinetics. The physico-chemical properties of CD Pickering emulsion were characterized by adsorption content, microstructure, rheology, and instability index. The results showed that the contact angles (85.30 & DEG; and 75.93 & DEG;), diffusion rates (-0.2481 and-0.1285), and adsorption rates (-0.0045 and-0.0028) of alpha-CD and 8 -CD were significantly higher than those of HP-CD derivatives, and emulsions possessed smaller droplet size (both about 7.5 mu m) and better stability compared with HP-CDs derivatives. The formation of Pickering emulsion was attributable to the interfacial adsorption layer structure at the oil-water interface formed by the self-assembly of CD. Subsequent studies on the physiochemical properties of emulsion showed that Pickering emulsions stabilized by alpha-CD and 8 -CD had better storage modulus, loss modulus, viscosity, storage stability, and centrifugal stability. HP-alpha-CD, HP -8 -CD, and HP-gamma-CD stabilized emulsions delaminated and sedimented within a short time. The amorphous HP-alpha-CD, HP -8 -CD, and HP-gamma-CD were difficult to form stable interfacial layers and adsorb on the surface of oil droplets due to their high-water solubility and poor crystallinity.

Automated summary

By studying the interfacial behavior of cyclodextrins and the physico-chemical properties of emulsions, it was found that Pickering emulsions stabilized by alpha-CD and 8-CD had better stability and rheological properties, while emulsions stabilized by HP-CD derivatives were prone to delamination and sedimentation.