A novel method to prepare water-soluble core microcapsules with controlled burst release

The controlled burst release of water-soluble materials from microcapsules is very important in many practical applications. A novel method is described to synthesize microcapsules containing water-soluble materials, ammonium persulfate or sodium nitrite, as the core and a hydrophobic copolymer (P(St–MMA)) as the shell through an evaporation–dispersion–polymerization process. The microcapsules had an average size of 8–16 μm. The release behavior was examined at different temperatures, pH values and salinities. The release pattern of the cores from the microcapsules was burst release. After a given time period in the 10–45 h region, all of the cores could be completely released within 1 h from the microcapsules. The structures, dispersion and morphologies of the microcapsules were characterized before and after they were stored for 5 months at room temperature. This method further enhances the potential of microcapsules with burst release properties for practical applications.