ZnGA/DMC catalysts for the synthesis of high molecular weight poly(propylene carbonate): The crucial role of water treatment

Zinc glutarate (ZnGA) is a prominent catalyst for the production of CO 2 -based poly(propylene carbonate). The original catalysts, ZnO-GA ( Cat 1 ) and ZnAc 2 -GA ( Cat 3 ), were prepared using ZnO and ZnAc 2 as Zn sources, respectively. ZnO-GA-H 2 O ( Cat 2 ) and ZnAc 2 -GA-H 2 O ( Cat 4 ) were prepared by water treatment of Cat 1 and Cat 3 , respectively. After water treatment, both Cat 2 and Cat 4 showed enhanced performance for copolymerization of CO 2 and propylene oxide. The characterizations demonstrated that H 2 O is a critical component that not only improves the crystallinity and external surface area of ZnGA, but also increases the number of surface Zn-OH groups. By adding a portion of cyanide, further modification on Cat 4 resulted in a group of ZnAc 2 -GA-H 2 O/DMC catalysts ( m-Cat 4 ). The polymerization reached a high yield of 1729 g poly/g Cat and a selectivity of 98.7 % at molar ratio of DMC/ZnGA = 1: 10 ( t = 24 h; T = 70 °C; P = 4 MPa). The modified ZnGA/DMC catalyst exhibited remarkable yield and selectivity for the copolymerization of CO 2 and propylene oxide to produce high molecular weight alternating copolymers (2.3 × 10 5 g/mol).