Ring-opening Polymerization of Cyclic Esters Using Recyclable Polystyrene Supported Urea-Base Binary Catalyst

To solve the catalyst residual problem, a promising strategy is to immobilize active catalyst on the surface of polymer microspheres to make heterogeneous catalyst. Herein, a metal-free approach to the ring-opening polymerization of lactones using recyclable polystyrene supported urea-potassium methoxide binary catalyst system is described. The new heterogeneous catalysts, polystyrene (PS) -supported cyclohexyl urea PS-U-1) and polystyrene-supported 4- (trifluoromethye) phenyl urea (PS-U-2) , were prepared by reactions of amine-functionalized PS microspheres with cyclohexyl isocyanate and 4- (trifluoromethyl) phenyl isocyanate, respectively. It was found that PS-U-potassium methoxide catalytic system exhibited high catalytic activity for ring-opening polymerization (ROP) of lactones, including epsilon-eaprolactone(epsilon-CL) , delta-valerolactone(delta-VL) and rac-lactide (rac-LA). In addition, the heterogeneous PS-U could be easily separated via simple filtration and recycled. It is worth noting that the recycled PS-U catalyst could be reused without significant decrease of catalytic activity.