Sakiko Tsuji

Thermosensitive pickering emulsion stabilized by poly(N-isopropylacrylamide)-carrying particles.

Poly(N-isopropylacrylamide) (PNIPAM)-carrying particles were characterized as thermosensitive Pickering emulsifiers. Emulsions were prepared from various oils, such as heptane, hexadecane, trichloroethylene, and toluene, with PNIPAM-carrying particles. PNIPAM-carrying particles preferentially formed oil-in-water (O/W)-type emulsions with a variety of oils. All the emulsions stabilized by PNIPAM-carrying particles were stable for more than 3 months as long as they were stored at room temperature. However, when the emulsions were heated from room temperature to 40 degrees C, at which point the PNIPAM layer caused a coil-to-globule transition, phase separation occurred. Thus, by using thermosensitive PNIPAM-carrying particles as emulsifiers, the stability of the Pickering emulsions could be controlled by a slight change in temperature.

Hairy particles prepared by living radical graft-polymerization

Novel particles having designed hairs were prepared by living radical graft-polymerization on core particles. The living radical species used in this study was a kind of photo-iniferter, N, N-diethyl-thiocarbamate. Main component of hair was poly(N-isopropylacrylamide) (PNIPAM) which was a representative thermo-sensitive polymer. The polymerization was carried out by UV irradiation at room temperature that was lower than the transition temperature of PNIPAM. Incorporation of a small amount of acrylic acid into the hair caused significant change in the properties of hairy particles. The mode of comonomer charge also enabled to design the hair structure on the particles.

Self-organization of poly(N-isopropylacrylamide)-carrying microspheres into two-dimensional colloidal thin films

Abstract A simple method to fabricate colloidal thin films with periodical structures was investigated. In this study, poly(N-isopropylacrylamide) (PNIPAM) microgel and polystyrene particles with PNIPAM chains on the surface (hairy particles) are used as components. Aqueous dispersions of these PNIPAM-carrying particles spontaneously form monolayers as water evaporates. After the medium is completely evaporated, periodical structures remain on the substrate. This paper focuses on the effect of graft chain density of the hairy particles on film formation.