Porogen effects in synthesis of uniform micrometer-sized poly(divinylbenzene) microspheres with high surface areas.

A new method of synthesizing uniform poly(divinylbenzene) (polyDVB) microspheres with high specific surface areas was designed by combining Shirasu porous glass (SPG) membrane emulsification, suspension polymerization, and post-crosslinking techniques. It was shown that the physicochemical properties of porogens have a great influence on the size distribution and porous features of microspheres. The low aqueous solubility of porogen facilitated preparation of uniform emulsions and microspheres, and high aqueous solubility led to polydispersed emulsions and poor microsphere yields. Such aqueous solubility effects can be tailored by adding a low molecular weight polystyrene (LPST) as costabilizer in porogen, thus improving the uniformity of microspheres. Moreover, different affinities of porogens for copolymers demonstrate various contributions to specific surface areas of microspheres in suspension polymerization especially post-crosslinking. Solvating porogen requires a much higher addition than nonsolvating porogen to obtain equal specific surface areas in polymerization, but has more potential to enhance the specific surface area in post-crosslinking. Two kinds of uniform microspheres were obtained with high specific surface areas, up to 706.6 m2/g by heptane and 937.5 m2/g by toluene.