Reinvestigation of the ring-opening polymerization of ε-caprolactone with 1,8-diazacyclo[5.4.0]undec-7-ene organocatalyst in bulk

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was used as organocatalyst to reinvestigate the ring-opening polymerization (ROP) of epsilon-caprolactone (CL) with benzyl alcohol (BnOH) initiator in bulk at 90 degrees C considering the unsuccessful ROP of CL at RT in previously reported publications. Kinetic study indicates that the PCLs could be well-designed with a controlled/living character of polymerization. The use of functional initiators, such as 2hydroxyethyl methacrylate (HEMA), propargyl alcohol (PGA), 6-azido-1-hexanol (AHA) and methoxy poly (ethylene glycol) (mPEG) leads to end-functionalized PCLs. Accordingly, the block copolymerization of CL with delta-valerolactone (VL), trimethylene carbonate (TMC) and lactide (LA) successfully proceeded to give PCL-b-PVL, PCL-b-PTMC and PCL-b-PLA copolymers. Finally, the reaction mechanism was studied with DFT calculations and NMR measurements.

Automated summary

8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was successfully used as an organocatalyst for the ring-opening polymerization (ROP) of epsilon-caprolactone (CL) with benzyl alcohol (BnOH) initiator, leading to well-designed PCLs with a controlled/living polymerization character. Functional initiators were used to obtain end-functionalized PCLs and successfully proceed with block copolymerization of CL with other monomers. Additionally, the reaction mechanism was studied through DFT calculations and NMR measurements.