Highly regioselective and alternating copolymerization of racemic styrene oxide and carbon dioxide via heterogeneous double metal cyanide complex catalyst

摘要

The highly regioselective racemic styrene oxide and carbon dioxide (SO-CO_2) copolymers with head-to-tail (HT) contents of ca. 96% and alternating degree 99% were successfully obtained by using heterogeneous nanosized zinc-cobalt(III) double metal cyanide complex (Zn-Co(III) DMCC) catalysts. A simple catalytic pathway was presented to control the stereochemistry during the copolymerization of CO_2 with a polar epoxide. Nanolamellar catalysts were synthesized using tert-butanol, tetrahydrofuran (THF), and ethylene glycol monomethyl ether as complexing agents, respectively. Initially, bulk CO_2-SO copolymerization was carried out at 90°C using nanolamellar catalyst. The productivity of this catalyst was excellent with a nearly complete SO conversion. Increasing reaction temperatures or decreasing CO_2 pressures resulted in relatively low HT contents, which suggested that more amounts of ether units in the copolymer chain caused low HT content.