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 mu m 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 degrees 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 degrees C and 45 degrees C, the released percents of Rhodamine B from TRHCs within 35 h were 25.7% and 70.9%, respectively. (C) 2011 Elsevier B.V. All rights reserved.