Tunable organo-catalysed ring-opening polymerization of ω-dodecalactone macrolactone by the cyclic triphosphazene base

Abstract

Degradable aliphatic long-chain polyesters (ALCPEs) with properties comparable to polyolefins are desirable as alternative substitutes for polyethylene. The preparation of ALCPEs by ring-opening polymerization (ROP) of macrolactones has the advantages of atom economy and controllable molecular weight in contrast to the polycondensation strategy. ω-Dodecalactone (DDL) is a derivative of the terpolymerization of 1,3-butadiene and has the potential to be produced on a large scale. Here, we demonstrated that the organobase cyclic triphosphazene base (CTPB) can serve as an efficient catalyst for the ROP of DDL. A high conversion of 95% can be achieved in less than 50 min at 80 °C and 1.0 M monomer concentration. Moreover, the ROP of DDL at 80 °C follows first-order kinetics. Poly(ω-dodecalactone-block-L-lactide) (PDDL-b-PLLA) block copolymers were obtained by the sequential addition of DDL and L-lactide (L-LA) and validated by NMR, DSC, and GPC. The synthesized poly(ω-dodecalactone-random-ε-caprolactone) (PDDL-r-PCL) random copolyester has an adjustable melting point (T_m). The PDDL-b-PCL block copolymer was also successfully obtained by reducing the basicity of CTPB by adding benzoic acid to decrease the activity of CTPB. The present work provides an efficient catalytic system for the facile synthesis of degradable ALCPE materials via the ROP of DDL, which is beneficial for promoting the large-scale production of ALCPEs.