A catalyst series of zeolitic imidazole frameworks (ZIFs) with a sodalite (SOD) structure was explored as an effective heterogeneous catalyst for l -lactide polymerization into biodegradable polylactides (PLAs). The catalyst series of ZIF-8, ZIF-67, and bimetallic ZnCo-ZIF was synthesized under the green method (room temperature synthesis), which contained a variance in the metal species/contents. The chemical and physical properties of catalysts were characterized by several techniques to illustrate the relation between catalyst properties and catalytic performance. The results indicated that the metals in the ZIF structure revealed an influencing role in catalytic activities, kinetic rates, and properties of polymer products under bulk ring-opening polymerization of l -lactide. Moreover, the best performing ZIF showed potential as a heterogeneous catalyst since it could be reused at least four times without significant loss of catalytic activity.
The synthesis of high-molecular-weight poly(ε-caprolactone)s (PCLs) with enhanced mechanical properties remains challenging. Here we demonstrate the heterogeneous catalysis for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). Using a zinc-cobalt double-metal cyanide complex [Zn-Co(III) DMCC] in the presence of around 1% mol epoxides, PCLs are achieved with high number-average molecular weights ( M n s) of up to 177.7 kDa determined by the gel permeation chromatography. The [Zn]-OH active site of the complex triggers the cleavage of the epoxide at first, which is considered as the rate-determining step of the polymerization. The formed zinc-alkoxide species then initiates the ROP of ε-CL, affording most of the PCLs possessing one epoxide molecule embedded in the polymer chain and dihydroxyl terminals as revealed by the 1 H NMR and MALDI-TOF MS spectroscopy. The PCL specimen with a corrected M n of 110.4 kDa exhibits the tensile strength and elongation at break of as high as 40.2 MPa and 1060%, respectively. This work provides a facile and practical method for the synthesis of high-molecular-weight PCLs.
危险品化学品经营许可证（带存储）