Controllable Ring-opening Polymerization of δ-Valerolactone Catalyzed by Quinolinyl-Urea/MTBD Systems

Due to their excellent biocompatibility and biodegradability, aliphatic polyesters are widely used in the biomedical, packaging and agricultural fields, which are usually accessed by the ring-opening polymerization (ROP) of lactones and the catalysts particularly play an important role. Herein a series of quinolinyl-urea catalysts have been synthesized via the reaction between isocyanate and aminoquinoline with an amino group at different substitution positions and characterized. In combination with 7-methyl-1, 5, 7-triazabicyclo[4,4,0]dec-5-ene (MTBD) as a cocatalyst and benzyl alcohol (BnOH) as an initiator, 1-(3,5-bis(trifluoromethyl)phenyl)-3-(quinolin-3-yl)urea (3-QU) was observed to be most active for the ROP of δ-valerolactone (δ-VL). The polymerization conditions were optimized by varying the type of organic base, catalyst concentration and reaction temperature. By changing the ratio of [M]₀/[I], linear polyvalerolactones (PVLs) with different molecular weights and narrow molecular weight distribution were prepared. The kinetic and chain extension experiments were carried out to prove the “living”/controllable feature. And the NMR experiments were used to support the proposal of possible mechanism.