Abstract:

The solubilization properties of ionic surfactants for polystyrene that was dissolved in carbon tetrachloride were determined by using a UV  method. The chloromethylation reaction of polystyrene was carried out in a micellar catalysis system, and the structure of chloromethylated polystyrene(CMPS) was characterized  by means of  FTIR and its composition was measured via  the  Volhard method. The catalysis effects of two types of anionic and cationic surfactants were compared; the catalysis effects of different cationic surfactants with different structures were examined; and the mechanism of micellar catalysis for chloromethylation reaction of polystyrene was explored. The experiment results show that a micellar solution of the surfactant can solubilize polystyrenes dissolved in CCl₄, namely, polystyrene can be transferred  into a micellar solution of surfactant along with solubilization of CCl₄ in the micellar solution of the surfactant. Micellar catalysis is an effective way to realize the  chloromethylation for polystyrene, and only 3.35 g/L  CTAB is needed for the  chloromethylation of  polystyrene with a 37%  chloromethylation degree at 65 ℃ within 5 h. The reaction mechanism of the reaction among polystyrene, formaldehyde and hydrochloric acid consists of two steps:  electrophilic substitution and nucleophilic substitution. The cationic surfactants are more effective than anionic surfactants, and the nucleophilic substitution step is a rate-controlling step. So it is appropriate to use cationic surfactants for realizing the chloromethylation of polystyrene. For cationic surfactants, the longer the hydrophobic carbon chain is, the better the solubilization property of surfactant is, so that its catalysis effect is better.                 

Key words: Polystyrene; Chloromethylation; Micellar catalysis; Surfactant