Mechanochemical synthesis of poly(lactic acid) block copolymers: overcoming the miscibility of the macroinitiator, monomer and catalyst under solvent-free conditions

Solvent-free green chemical synthesis of poly(lactic acid) (PLA) block copolymers was achieved via a mechanochemical method from macroinitiators. High-speed ball-milling of the lactide, macroinitiator, and organocatalyst (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU) eliminated the need for a chemical solvent and produced a series of di-and tri-block copolymers containing PLA blocks with an excellent efficiency. High impact collisions between balls and a vessel provided sufficient mixing such that reactive chain-ends buried in polymeric domains were able to react with DBU and lactides, thus eliminating the need for chemical solvents.