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

In order to obtain homogeneously sulfonated cation exchangers, the copolymers were sulfonated 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.