Effect of porosity on sulfonation of macroporous styrene-divinylbenzene beads

Macroporous styrene-divinylbenzene beads having pore volume in the range of 0.1-2.2 ml/g were synthesized by o/w suspension polymerization using petroleum ether and cyclohexanone as porogen. As the pore volume was increased the pore size distribution shifted towards large pore diameter and the mechanical strength of the beads in the dry state decreased. The copolymers were converted into cation-exchange resins by sulfonation under controlled experimental conditions. The derived resins had the highest capacity when the base copolymers had pore volume in the range of 0.3-0.4 ml/g. The results are explained on the basis of the effect of the porogen on the spaces between chains and cross-links in the copolymer phase and the permanent pores in the beads.