Surfactant-free emulsion copolymerization of styrene and a cationic comonomer with two positively charged groups

Near-monodisperse, stabilized latex particles were prepared by surfactant-free emulsion copolymerization of styrene with a water-soluble cationic comonomer StMV having two positively charged groups. Unlike previously reported surfactant-free emulsion copolymerization systems, very small polymer nanoparticles (≤ 70 nm as indicated by transmission electron microscopy studies) were produced even though the StMV/St molar ratio was no more than 1/100. The effects of initiator concentration, StMV concentration, and styrene concentration on the size of the latex particles were investigated. The polymerization kinetics was monitored by transmission electron microscopy, monomer conversion, dynamic light scattering, and visual inspection. This study is expected to enrich the surfactant-free syntheses of cationic polystyrene latex and can provide useful information to construct cucurbit[n]uril-based supramolecular polymer colloids.