Abstract
The reaction between diazonium salts and hypophosphorous acid, reported in the literature as a free radical reaction, has been used to initiate the polymerisation of acrylonitrile. A 5-fold excess of hypophosphorous acid, as compared with the diazonium salt, was found suitable, and the diazonium salts were usually present at 2% of the molar concentration of the acrylonitrile. Oxidizing agents in some cases accelerate polymerisation, and copper sulphate, the effect of which was examined in detail, is particularly efficient in this respect at very low concentrations. Representative polymers were analysed, and found to contain permanently bound phosphorus. A comparison of the number average molecular weights derived therefrom with viscometric molecular weights indicates that there is one atom of phosphorus for each molecule of polymer. The effect of different diazonium salts has been examined in some detail. Nucleophilic substituents on the benzene ring reduce the efficiency of polymerisation, which is accelerated by electro-philic substituents. The system diazonium salt-sodium bisulphite has been found to act as a redox system leading to the polymerisation of acrylonitrile.