A new emulsion method to synthesize well-defined mesoporous particles.

A new emulsion method for preparing ordered mesoporous materials with polymer PEG as the swelling agent has been explored in the present work. The synthesis conditions including the chain length and the PEG concentration, the duration of aging, the kind of emulsion, and the time when the swelling agents were added to the reaction system are discussed. The results show that with the advantage of the emulsion method, the nucleation and growth were controlled very well. The nicely spherical particles produced by the emulsion method were more uniform and less prone to agglomerate than those produced through the hydrothermal method. When different MW PEG were added as swelling agents, the pore size changed little: it was centered around 4 nm and had a narrow distribution. When different concentrations of PEG were applied, BET surface area, pore size, and pore volume changed. To summarize, in the formation of mesoporous materials, polymers such as PEG can not only control the pore size from 3 to 70 nm through variation of concentration, but also regulate the structures and improve the morphology of particles by the chain length of polymers. By adjusting the time of addition of the swelling agents, a poroshell mesoporous material was prepared. This method is particularly important for those applications that strictly require particle uniformity, such as chromatography separation.