Miniemulsion polymerization templates: A systematic comparison between low energy emulsification (Near-PIT) and ultrasound emulsification methods

Poly(ethylene oxide)-covered polystyrene nanoparticles were prepared by free radical miniemulsion polymerization after using an original low energy emulsification procedure called Near-PIT method. This procedure consisted in heating the initial monomer emulsion up to a temperature close to the phase inversion temperature (PIT) but lower. The surfactants used were commercial Brij® 78 and Brij® 700 and mixtures of both. The Near-PIT method was showed to allow the preparation of nanoparticle suspensions with average diameters lower than 100 nm and solid contents higher than 20 wt% while avoiding heating the initial monomer emulsion above PIT like in usual low energy methods. The influences of various formulation and operating parameters were investigated. Finally, the Near-PIT method was compared to other well-known procedures for nanoparticle preparation, miniemulsion polymerization after ultrasound emulsification and macroemulsion polymerization under mechanical agitation. The performances of Near-PIT procedure were comparable to ultrasound emulsification.