Fast and controlled ring-opening polymerization of δ-valerolactone catalyzed by benzoheterocyclic urea/MTBD catalysts†
Aliphatic polyesters are a class of biorenewable, biocompatible, and biodegradable materials. The ring-opening polymerization (ROP) of lactones is one of the most powerful methods to access these materials. A novel series of benzoheterocyclic urea catalysts has been synthesized and characterized. When employed in the ROP of δ-valerolactone (δ-VL) in combination with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), a fast and “living”/controlled feature was observed in both solvent-free polymerization and solution polymerization, which was proved by kinetic and chain extension experiments. With benzyl alcohol as an initiator, polyvalerolactones (PVLs) were obtained with different molecular weights and narrow molecular weight distributions. In addition, the PVLs with different topological structures were prepared by varying the initiators. The structure and thermal properties of resulting polymers were determined by NMR, GPC and DSC analyses. A possible mechanism was also proposed on the basis of NMR analysis.