Micron-sized polystyrene particles by surfactant-free emulsion polymerization in air: Synthesis and mechanism

In this study, we propose an alternative method to produce high solids, micrometer-sized polystyrene (PS) latexes with narrow size distribution, based on the use of large amounts of polymerization initiator and allowing the presence of oxygen in the reaction vessel. We have demonstrated that the deoxygenation of the reaction mixture in surfactant-free emulsion polymerization becomes redundant if enough radical initiator is employed, and that particles with narrow size distribution can be obtained in the presence or absence of oxygen. The significance of this method lies in its simplicity and robustness: the method requires only a single-neck flask sealed with a rubber septum, a magnetic stirrer, and an oil bath. We also show that the use of large amounts of radical initiator allows the preparation of latexes with particularly high solid contents (up to 20 wt %), which is uncommon in systems with no added stabilizing agent.