Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels

Background: Emulsions stabilized by colloidal particles are known as Pickering emulsions. To date, soft microgel particles as well as inorganic and organic particles have been utilized as Pickering emulsifiers. Although cyclodextrin (CD) works as an attractive emulsion stabilizer through the formation of a CD–oil complex at the oil–water interface, a high concentration of CD is normally required. Our research focuses on an effective Pickering emulsifier based on a soft colloidal CD polymer (CD nanogel) with a unique surface-active property. Results: CD nanogels were prepared by crosslinking heptakis(2,6-di-O-methyl)-β-cyclodextrin with phenyl diisocyanate and subsequent immersion of the resulting polymer in water. A dynamic light scattering study shows that primary CD nanogels with 30–50 nm diameter assemble into larger CD nanogels with 120 nm diameter by an increase in the concentration of CD nanogel from 0.01 to 0.1 wt %. The CD nanogel has a surface-active property at the air–water interface, which reduces the surface tension of water. The CD nanogel works as an effective Pickering emulsion stabilizer even at a low concentration (0.1 wt %), forming stable oil-in-water emulsions through interfacial adsorption by the CD nanogels. Conclusion: Soft CD nanogel particles adsorb at the oil–water interface with an effective coverage by forming a strong interconnected network and form a stable Pickering emulsion. The adsorption property of CD nanogels on the droplet surface has great potential to become new microcapsule building blocks with porous surfaces. These microcapsules may act as stimuli-responsive nanocarriers and nanocontainers.

Synthesis and Characterization of Dehydroabietic-Based Phosphate Betaine Type Amphoteric Surfactant

N-(3-dehydroabietyloxy-2-hydroxy) propyl-N, N-dimethyl (2-hydroxy) phosphate betaine was synthesized through the 3-dehydroabietyloxy-2-hydroxypropyl chloride and tertiary amine intermediate by using dehydroabietic acid as raw materials. The structure of the target product was confirmed by FT-IR, 1H NMR. The surface-active property was investigated by surface tension experiment. The surface activity of the mixed system of the product and sodium dodecyl sulphate (SDS) was determined. The results showed that critical micelle concentration (CMC) of the product was 1.34 mmol•L-1. Strong synergism in product was observed combining with SDS, and the optimum synergism was obtained at the molar ratio of 1:1.