Accelerating effect of crown ethers on the lactide polymerization catalysed by potassium acetate

Recent advances in catalysis enriched the toolbox to prepare well-defined polyester materials such as polylactide (PLA). Herein, we report the use of crown ethers to speed up the polymerization of l-lactide (l-LA) initiated by an exogenous alcohol and catalyzed by potassium acetate (KOAc). With KOAc, the crown ethers played a crucial role as a complexing agent, with 18-crown-6 enabling the fastest polymerization kinetics outpacing the one obtained with the pristine catalyst by not less than 73. Experimental results suggested that the 18-c-6 crown ether complexed the KOAc ion pair to in situ produce free ions, which was much more appropriate to activate the propagating alcohol for the ring-opening reaction of l-LA.

Automated summary

In this experiment, crown ethers were used to accelerate the polymerization of l-lactide initiated by an exogenous alcohol and catalyzed by potassium acetate. Among the crown ethers tested, 18-crown-6 showed the fastest polymerization kinetics, outperforming the pristine catalyst by at least 73%. This was attributed to the complexation of the KOAc ion pair by 18-crown-6, which facilitated the activation of the propagating alcohol for the ring-opening reaction of l-LA.