Facile method to prepare monodisperse polystyrene particles by hydrothermal process

A facile method to prepare monodisperse polystyrene (PS)/cross-linked PS particles was studied by combining hydrothermal process with dispersion polymerisation. Compared to traditional dispersion polymerisation, in this way the polymerisation of styrene in ethanol–water media could be carried out in a relatively wide ethanol/water ratio range from 10/90 to 70/30, consequently monodisperse particles from 160 to 1300 nm in size were generated at 80°C. It implies that the monodisperse PS particles could be acquired simply and the significant change in PS particle size could be adjusted by only varying the ethanol/water ratio. The phenomenon could be inferred that the hydrothermal process improved the solubility of the monomer in the media under a higher reaction pressure, which enabled this method to expand the ethanol/water ratio range for traditional dispersion polymerisation. Furthermore, the monodisperse cross-linked PS particles could also be obtained even at the cross-linking agent being up to 2% without addition of stabiliser through this method. Not using stabiliser could enlarge the application range of the cross-linked monodisperse PS particles. The formation process of the particles was detected using scanning electron microscopy. The particle morphology transformation along with hydrothermal reaction in the early stage was demonstrated, that is, the initial irregular particles in different size congregated gradually to form monodisperse particles.