CO-Controlled One-Pot Synthesis of AB, ABA Block, and Statistical Terpolymers from β-Butyrolactone, Epoxides, and CO.

Terpolymerizations of (rac)-β-butyrolactone (BBL), cyclohexene oxide (CHO), and carbon dioxide were realized in one-pot reactions utilizing a Lewis acid BDI-Zn-N(SiMe) (1) catalyst. The type of polymerization can be regulated and switched between ring-opening polymerization (ROP) of BBL and CHO/CO copolymerization by the presence of CO in the reaction mixture. Applying 3 bar CO to the three-component system leads to similar reaction rates for copolymerization and ROP and therefore to a terpolymer with a statistical composition, whereas 40 bar CO affords exclusive copolymerization of CHO/CO. Two-dimensional NMR spectroscopy and polarimetry provided a deeper understanding of the underlying mechanism. Furthermore, copolymerization of cyclopentene oxide (CPO) and CO was performed, resulting in the highest reported TOF of 3200 h together with 99% polycarbonate selectivity. Terpolymerizations of CPO/CO and BBL were successfully conducted using the established reaction pathways.