Homogeneous Sulfonation of Styrene‐Divinylbenzene Copolymers with Oleum in Organic Solvents

Abstract

In order to obtain homogeneously sulfonated cation exchangers, the copolymers were s1'.1fonated by oleum in a mixture of methylene-chloride and nitromethane. The influences of the chemical interaction and of the diffusion process on the kinetic behavior of these systems were investigated, and it was shown that raising the temperature of the sulfonation mixture markedly increases the chemical reaction rate, while the effect on the diffusion is small. A curve-fitting technique was used for the interpretation of the degree-of-sulfonation-vs.time curves. These investigations served as guidelines for the subsequent preparation of homogeneous highly sulfonated copolymers.

Effect of the Sulfonation on the Swollen State Morphology of Styrenic Cross-Linked Polymers

“…All these results are completely in line with the well-known circumstance that the formation of sulfone bridges is a side reaction of the sulfonation with oleum and chlorosulfonic acid [11,15,19,20]. According to the literature [21], it involves the acid catalyzed condensation of two sulfonic group, in which the use of a very strong acid and dehydrating agent such as oleum is expected to favour both the protonation of the sulfonic groups and the subsequent elimination of water. Moreover, in doubly sulfonated rings, the acidity of the sulfonic groups is significantly enhanced [18], due to the deactivation of the aromatic unit, and the protonation step is expected to be even more effective.…”