Performance of ionic liquid as catalyst in the copolymerization of phenyl glycidyl ether with carbon dioxide

The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed using ionic liquid as catalyst in a semi-batch reaction with a continuous supply of carbon dioxide. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C-2, C-4, C-6, C-8) and anions (Cl-, BF4-, PF6-) were used for this reaction carried out under constant pressure. All the 1-alkyl-3-methyl imidazolium chlorides showed very high carbonate content. The turnover number (TON) and average molecular weight of the copolymer were affected by the structure of the imidazolium salt ionic liquid; the one with the cation of longer alkyl chain length and with more nucleophilic anion showed better reactivity. However, TON decreased when hexyl or octyl containing ionic liquids were used probably due to their steric hindrance. The effects of reaction temperature, carbon dioxide pressure, and reaction time on the carbonate content and TON of the polycarbonates are also discussed. Tetrabutylammonium chloride (TBAC) was also tested for this reaction to compare its catalytic performance with the ionic liquids.