The Magic of Organocatalytic Synergism in Switchable Polymerization: One-pot Synthesis of Block Copolymers with Programmable Sequences and Compositions

Switchable polymerization is emerging as a powerful tool to construct block copolymers directly from mixtures of monomers. However, current achievements typically iterate between two polymerization cycles to afford products with fixed sequences and compositions. Herein, we report the triethylborane/1,8-diazabicyclo[5.4.0]undec-7-ene (Et 3 B/DBU) pair-mediated four-component switchable polymerization of propylene oxide (PO), CO 2 , phthalic anhydride (PA), and racemic lactide ( rac -LA), which enables the on-demand synthesis of four different block copolymers, i.e. , poly(propylene phthalate)- b -polylactide (PPE- b -PLA), PPE- b -PLA- b -poly(propylene carbonate) (PPC), PPE- b -PPC- b -PLA, and PPE- b -PPC- b -poly(propylene oxide) (PPO), through rationally modulating the Lewis pair (LP) ratio. Core to this protocol is that increasing the loading of Et 3 B accelerates the ring-opening of PO while impeding the reactivity of rac -LA, thus allowing for fine-tuning of the thermodynamic and kinetic of the switchable polymerization. Therefore, the four polymerization cycles involving PO/PA ring-opening copolymerization (ROCOP), PO/CO 2 ROCOP, rac -LA ring-opening polymerization (ROP), and PO ROP can be connected and discriminated in precisely programmed manners.