Air- and Moisture-Stable Indium Salan Catalysts for Living Multiblock PLA Formation in Air

We introduce an air- and moisture-stable hydroxy-bridged indium salan complex as a highly active and controlled catalyst for the ring-opening polymerization of cyclic esters in air. The reversible activation of this complex with linear and branched alcohols leads to immortal polymerization, allowing the controlled formation of block copolymers in air. It is the only reported example of a living catalyst that remains controlled after multiple exposures to ambient air at high temperatures. Although the prevalent catalyst for ring-opening polymerization, tin octanoate, is robust, it does not promote controlled polymerization. Our indium catalyst is exceptional in being both robust and controlled.