Porous structure of highly crosslinked styrene-divinylbenzene copolymers

Porous structure of two series of styrene (S)-divinylbenzene (DVB) copolymers has been studied. The copolymers were prepared by suspension copolymerization of the monomers (50 wt.-% of DVB) in the presence of heptane-toluene mixtures as inert diluents. The fraction of diluents in the polymerization system or heptane: toluene ratio was changed. Both the pore volume and specific surface area increase as does dilution or the fraction of heptane in diluents, but the measured values change depending on sample pretreatment. A mechanism of structure built up is discussed and the porosity changes explained in terms of a microsyneresis of inhomogeneous S-DVB copolymer gel.