Synthesis of temperature-responsive hybrid capsules and their controlled release property

In this work, a temperature-responsive hybrid capsules (TRHCs) was prepared from inverse pickering emulsion polymerization route. The aqueous solution of N-isopropyl acrylamide and poly (N-isopropyl acrylamide) was emulsified into an oil phase containing divinyl benzene (DVB) by sonication to obtain a water-in-oil (W/O) pickering emulsion stabilized by modified silica nanoparticles. Then the emulsion was polymerized to obtain the hybrid capsules. The sizes of the capsules are about 5–10 μm and can be tuned by the modified silica nanoparticles concentration in continuous phase. The capsules wall consists of two layers: a solid particle layer and a polymer layer, whose thickness can be conveniently controlled by adjusting the DVB concentrations in the continuous phase before polymerization. The as-synthesized capsules exhibit good temperature-responsive property with a phase-transition temperature of 27 °C. The controlled release experiment shows that the release rate of a model drug (Rhodamine B) from the hybrid capsules can be controlled by adjusting the temperature of the release medium. When the medium temperatures were 25 °C and 45 °C, the released percents of Rhodamine B from TRHCs within 35 h were 25.7% and 70.9%, respectively.