Monodisperse polystyrene microspheres containing quaternary ammonium salt groups by two-stage dispersion polymerization: effect of reaction parameters on particle size and size distribution

A facile approach to prepare monodisperse polystyrene (PS) particles containing quaternary ammonium salts with long alkyl chain was reported. The PS particles containing quaternary ammonium salts are prepared by two-stage dispersion polymerization in ethanol/water (80/20 w/w) mixture with polyvinylpyrrolidone (PVP) as a steric stabilizer and fatty alcohol polyoxyethylene ether (AEO-9) as a co-stabilizer. Polymerizations are conducted using N '-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide (QDMDB) as a comonomer added in the second stage. We identify reaction conditions where one can obtain the functional polystyrene microspheres with a size distribution less than 3%. The influence of the initiator concentration, the styrene monomer concentration, the stabilizer concentration, and QDMDB comonomer concentration on the average particle size and the efficient of variation are investigated comprehensively. The novel particles are examined using scanning electron microscopy (SEM), gel permeation chromatography (GPC), zeta potential, and nuclear magnetic resonance (H-1 NMR). QDMDB comonomer not only functionalized the polystyrene particles but also proved to be effective in controlling the particle size and size distribution. According to these results, we show that two-stage dispersion polymerization is an effective pathway for the structure design of the functional microspheres.