Syntheses of high molecular weight aliphatic polyesters in 1-alkyl-3-methylimidazolium ionic liquids

High molecular weight aliphatic polyesters were synthesized, for the first time, in 1-alkyl-3-methylimidazolium ionic liquids via two-step polycondensation. An oligoester with diol/diacid ratio higher than unity was essential for achieving high molecular weight product. Moreover, the molecular weight of the resulting polyesters was found to depend on the activity of the catalyst in the ionic liquids and the miscibility of aliphatic polyester/ionic liquid. The former factor was dominated by the anion of the ionic liquids. The latter factor could readily be tuned by varying the anion and/or the cation of the ionic liquids. A clear correlation was found between the miscibility of aliphatic polyester/ionic liquid and the extent to which their solubility parameters matched.