Friedel-Crafts crosslinking methods for polystyrene modification: 1. Preparation and kinetics

A two-step polymerization and grafting-crosslinking reaction was developed for modification of polystyrene. Styrene was first polymerized in dichloroethane at 25°C using SnCl₄ as catalyst. The cationically prepared polystyrene was then grafted with 1,4-dimethyl-2,5-dichloromethyl benzene in dichloroethane at 50°C in a Friedel-Crafts reaction system. The kinetics of the reaction were followed by titrating the evolved HCI from the reaction system. The maximum reaction rate was found to vary with both the initial concentration of 1,4-dimethyl-2,5-dichloromethyl benzene and the initial concentration of SnCl₄. Determination of the concentration of junctions of the grafted polystyrene samples and analysis of their u.v. spectra were used to determine the progress of the reaction, and to propose a reaction mechanism.