Organobase-Catalyzed Ring-Opening Copolymerization of Cyclic Anhydrides and Oxetanes: Establishment and Application in Block Copolymer Synthesis

Polyesters are a prominent class of polymer materials. The ring-opening copolymerization (ROCOP) of cyclic anhydrides and cyclic ethers has attracted attention as a method for the precise synthesis of a variety of polyesters. However, epoxides have been the primary cyclic ether employed in this method, and precise polymerization with oxetane has been challenging. This paper accomplished organobase-catalyzed ROCOP of cyclic anhydrides and oxetanes for synthesizing polyesters. By applying t-BuP2 as a catalyst for the ROCOP of phthalic anhydride (PA) and trimethylene oxide (TO), perfectly alternating P(PA-alt-TO) was obtained with predictive molecular weights ranging from 3000 to 20,000 Da and low dispersities (Đ < 1.16). A kinetic experiment on the ROCOP of PA and TO confirmed the controlled/living nature of the proposed ROCOP system. Furthermore, its remarkable tolerance for various functional groups facilitates the utilization of a wide range of monomers and initiators, resulting in polyesters with distinct glass transition temperatures (Tg, −45.4 to 60.8 °C). Moreover, this polymerization process can be seamlessly integrated with other ROCOP processes, such as the ring-opening polymerization of trimethylene carbonate, valerolactone, or l-lactide and the ROCOP of PA/epoxide; this enables the synthesis of polyester-based block copolymers in a one-pot/one-step manner, known as self-switchable polymerization. Consequently, this novel polymerization process expands the scope of the existing ROCOP approaches and paves the way to synthesizing diverse polyesters with tailored material properties.