Cloromethylation of styrene-divinylbenzene copolymer (S-DVB) in presence of hydrogen chloride, formaldehyde and zinc chloride was studied in aqueous and organic media. S-DVB was first synthesized by suspension polymerization and its porosity was characterized. In aqueous medium, S-DVB was chloromethylated by using a mixture of hydrogen chloride, aqueous formaldehyde solution (formalin 37%) and aqueous zinc chloride solution as catalyst. In organic medium (1,2-dichloroethane), a mixture of hydrogen chloride, paraformaldehyde and solid zinc chloride was employed. The presence of chloromethyl groups in the copolymer was investigated by infrared spectroscopy analysis and titration of chloride ions, after a quaternization reaction between the chloromethylated copolymer and pyridine. The reaction in aqueous medium seems to be very difficult to occur even in the presence of solid zinc chloride (catalyst) and concentrated hydrochloric acid as reaction medium. Organic medium offers a better condition for aromatic eletrophilic substitution, where the reaction occurred in a more satisfactory way. The influence of reaction parameters was studied. Temperature and copolymer/catalyst ratio were the main responsible factors for the attained chloromethylation degree.
Chloromethylation; styrene-divinylbenzene copolymers; hydrogen chloride; formaldehyde; zinc chloride
