title: Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Biomaterial and Commodity Chemicals Research Division, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Kawano
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kida
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Akashi
authors.affiliation: Biomaterial and Commodity Chemicals Research Division, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Sato
authors.affiliation: Biomaterial and Commodity Chemicals Research Division, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Shizuma
authors.affiliation: Biomaterial and Commodity Chemicals Research Division, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ono
keywords: Pickering emulsion; crosslinked cyclodextrin polymer; interfacial adsorption; nanogel