Synthesis of macroporous poly(styrene-co-divinylbenzene) microparticles using n-heptane as the porogen:: Quantitative effects of the DVB concentration and the monomeric fraction on their structural characteristics

Macroporous poly(styrene-co-divinylbenzene) microparticles from reactive mixtures with various divinylbenzene and diluent contents have been synthesized. n-Heptane, which is a poor solvent for the copolymer, was used as diluent of the organic phase during the polymerization to obtain a high percentage of meso- and macropores, which are the most useful pores in the adsorption of macromolecules of medium and large sizes, such as proteins. The research was planned through a factorial design of experiments in an attempt to determine a quantitative relationship between the pore characteristics of the microparticles obtained and the concentration of the divinylbenzene and of the diluent used in the reactive mixture. The nitrogen adsorption-desorption isotherm and the curve of mercury intrusion for each type of microparticle were obtained, and the BET-specific surface areas and the volumes of macro-, meso-, and micropores were determined. Finally, empirical models correlating the synthesis conditions with the BET-specific surface area and the volumes of the micro-, meso-, and macropores were calculated; it was observed that the higher the divinylbenzene concentration in the monomeric mixture, the higher the volumes of micro- and mesopores and the larger the BET-specific surface area. It was also concluded that the higher the amount of diluent, the higher the volumes of meso- and macropores. Within the scope of the work, these models permit the synthesis of adsorbents with predetermined pore properties.