Preparation of Peanut-Shaped PS Nanoparticles Through Emulsion Polymerization by Using Styrene-Maleic Anhydride Copolymer as the Cosurfactant

Anisotropic particles have garnered significant attention due to their unique structural characteristics, and emulsion polymerization is one of the synthesis strategies. In this study, for the first time, poly(styrene-maleic anhydride) (SMAA) and small-molecule surfactant were employed as the composite emulsifiers during the emulsion polymerization of styrene (St) for synthesizing peanut-shaped polystyrene (PS) nanoparticles. The results of NMR, FTIR, and SEM confirmed this method was reliable. Furthermore, the polymerization conditions were optimized by using particle morphology as the primary optimization parameter. The optimized polymerization conditions are as follows: St concentration of 11 wt%, emulsifier concentration of 0.6 wt% in water, the emulsifier being a composite system of sodium dodecylbenzenesulfonate (SDBS) and SMAA in a mass ratio of 1:2, initiator concentration of 0.5 wt% (relative to St mass), crosslinker dosage 0.6 wt% (relative to St mass), reaction temperature of 70°C, and the reaction duration of 6 h. The resulting polymer products exhibited a distinct peanut-like morphology, with an average particle diameter of 54.1 nm and an aspect ratio of 2.44. These findings provide some novel insights into the preparation of anisotropic particles.