Highly crosslinked poly(acrylamide-co-divinylbenzene) microspheres by precipitation polymerization

Highly crosslinked poly(acrylamide-co-divinylbenzene: AAm-co-DVB) microspheres with various compositions of DVB were prepared by precipitation polymerization in acetonitrile or acetonitrile/water media, and their characteristics investigated. The number-average particle diameter and the yield of polymerization increased from 1.17 to 1.42 mu m and from 56.2 to 68.7%, respectively, while the coefficient of variation decreased from 16 to 5.5%, upon increasing the content of DVB from 20 to 75 mol%. However, with 10 mol% of DVB, the spherical particles coagulated after the initial stage of the polymerization. By increasing the concentration of DVB from 20 to 75 mol%, the experimentally measured specific surface area decreased correspondingly from 5.87 to 4.32 m(2)/g; this result implies that the particles were individually present without coagulum or free of pores and that their surface smoothness was enhanced. Regarding the thermal stability, the weight loss between 300 and 500 degrees C dramatically improved with increasing DVB content because of the high degree of crosslinking. In addition, when water was employed as a co-medium with acetonitrile, and the acetonitrile-to-water ratio was varied between 5:1, 7: 1, and 9: 1, the average particle size decreased from 3.5, to 3.0, to 2.5 mu m, respectively; the coefficient of variation of the particles also improved while the specific surface area changed slightly.