Preparation of pH Responsive Polystyrene and Polyvinyl Pyridine Nanospheres Stabilized by Mickering Microgel Emulsions

Abstract

New pH-sensitive polystyrene, PS, and poly(4-vinylpyridine), P4-VP, nanospheres were prepared by using surfactant-free method based on soft microgels (Mickering emulsion). The formation of stable Mickering cyclohexane/water emulsions was investigated by using soft microgel particles of poly(acrylamide), PAAm, poly(2-acrylamido-2-methylpropane sulfonic acid), PAMPS, and sodium salt of PAMPS, PAMPS-Na, as stabilizers. The dynamic light scattering (DLS), optical microscopy, and scanning electron microscopy (SEM) were used to investigate the optimum conditions and effects of surrounding solutions on the microgels characteristics and their corresponding Mickering emulsions. The cyclohexane/water Mickering emulsions stabilized by softer and neutral charged microgels were considerably more stable under the same conditions. Furthermore, the stimuli-responsive properties of PAMPS microgel stabilized cyclohexane/water Mickering emulsions suggest the potential utility in the preparation of PS and P4-VP nanospheres. The effects of pH changes on the morphology, particle sizes, and surface charges of PS and P4-VP microgels were evaluated to prove the pH-sensitivity of the prepared nanospheres.