Effect of iodide additives on the polymerization of 2,6-dimethylphenol with copper bromide n-butylamine catalyst

The effects of three iodide additives on the performances of two 2,6-dimeth ylphenol polymerization catalysts based on copper bromide were studied. The iodide additives were sodium iodide, potassium iodide and methyl iodide. T he polymerization catalysts were CuBr2/n-butylamine and Cu2O/HBr/n-butylami ne. Iodide addition resulted in the higher polymer molecular weight which d ecreased in the following order: NaI > KI > CH3I. Polymerization induction period increased significantly with NaI addition, but was insensitive to th e concentrations of KI and CH3I. Addition of quaternary ammonium salt to th e NaI-added catalyst dramatically shortened the induction period and greatl y decreased the amount of copper catalyst needed. UV-VIS absorption spectro scopy showed that the Br-->I exchange occurred with the addition of NaI int o the copper bromide-based catalyst. Besides, I-->Cl exchange was observed with the addition of methyltrioctylammonium chloride to the NaI-added catal yst. The I-->Cl exchange was caused by the binding of the iodide anion to t he quaternary ammonium cation. Copper chloride/n-butylamine complex was gen erated after the I-->Cl exchange.