Preparation of open cellular PMMA microspheres by supercritical carbon dioxide foaming

Poly(methyl methacrylate) (PMMA) microspheres with a nonporous skin and open cellular core structure were obtained by supercritical carbon dioxide foaming via a pressure quench method. The microspheres were characterized by particle size analyzer, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Effects of foaming conditions such as CO2 pressure, temperature, and cell growth time on the particle size, size distribution, and morphology of the PMMA microspheres were investigated in detail. It was found that higher foaming temperature and higher pressure resulted in an increase of particle size. However, a longer cell growth time caused a decrease in size of the foamed PMMA microspheres.