Kinetics of styrene miniemulsion polymerization using poly[(stearyl methacrylate-co-(N,N-dimethylamino)ethyl methacrylate] as surfactant

Two comb-like amphiphilic copolymers have been prepared via conventional free-radical random copolymerization of stearyl methacrylate (SMA) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) with different feed ratios. The resultant copolymers, poly(SMA-co-DMAEMA), were then characterized by 1H NMR and gel permeation chromatography (GPC) measurements. The surface activity of these copolymers in aqueous solution with different pH values was studied by surface tension measurements. Finally, these amphiphilic cationic copolymers were used as polymeric surfactants in the miniemulsion polymerization of styrene. The hydrophobic stearyl side chains of SMA could be strongly adsorbed onto the monomer droplets or propagating particles during the miniemulsion polymerization, while the hydrophilic and protonated PDMAEMA units at low pH media could stabilize the latexes. Moreover, the influences of the composition and amounts of the polymeric surfactants on the kinetics of the miniemulsion polymerization and colloidal stability have been investigated. The reaction rate of miniemulsion polymerization was found to increase with increasing amounts of polymeric surfactants and decrease with the increase of pH values of aqueous solution.