Polymeric nanocapsules with controllable crosslinking degree via combination of surface-initiated atom transfer radical polymerisation and photocrosslinking techniques.

The crosslinked polystyrene nanocapsules with controllable crosslinking degree have been prepared by the ultraviolet (UV)-induced photocrosslinking of the polystyrene grafted silica nanoparticles (SN-PS), which was obtained by the surface-initiated atom transfer radical polymerisation of styrene from the modified silica nanoparticle templates, after the silica templates were etched with hydrofluoric acid. The effect of the UV-irradiating time on the inner diameter of the nanocapsules, and the degree of crosslinking and the thickness of the shells was investigated. The dynamic light scattering results showed that the degree of crosslinking of the obtained nanocapsules increased with the prolongation of the UV-irradiation time, therefore the inner diameter of the nanocapsules increased. However, the percentage of grafting of the crosslinked polymer shells decreased with increasing the UV-irradiation time because of the photodecomposition of the polystyrene grafted during the UV-irradiated crosslinking process, according to the thermogravimetric analysis.