Synthesis and Performance Study of pH/Magnetic Dual Response Chitosan Based Emulsifiers

Abstract

Recently, stimuli-responsive emulsions have been widely applied due to their excellent structural stability, biocompatibility, and environmental friendliness. For this application, the emulsion needs to be able to respond quickly to environmental stimuli with controlled stabilization and destabilization. This paper reports a novel composite Pickering emulsifier using Fe3O4 as the core, silica as the intermediate layer, and chitosan as the outer shell, which possesses a pH/magnetic dual responsive feature when deionized water is used as the water phase, and liquid paraffin is used as the oil phase to form an emulsion. Fe3O4@SiO2@chitosan has good paramagnetism and pH responsiveness to realize controlled magnetic and pH-responsive breaking of an emulsion when needed. The size of the composite emulsifiers ranged from 90 nm to 120 nm. The strong magnetic responsiveness enables rapid emulsion breaking at pH=3-11. When used as stabilizer particles, the chitosan shell behaves differently depending on pH. At pH≤2, fully protonated chitosan as the free chain segment and Fe3O4@SiO2 stabilized emulsions together. The overall stabilization of the emulsion (Fe3O4@SiO2@chitosan as emulsifier) can be obtained at pH>2, and emulsion breaking is achieved at pH≈pKa condition.