Direct ring-opening of lactide with amines: application to the organo-catalyzed preparation of amide end-capped PLA and to the removal of residual lactide from PLA samples

Amide end-capped PLA can be efficiently prepared by taking advantage of the ability of amines to ring-open lactide. A two-step one-pot strategy has been developed in which primary or secondary amines are reacted with an excess of lactide prior to the addition of the ROP catalyst, DBU. Amide-functionalised PLA of different structures (linear, telechelic, star-shaped etc.) have been prepared using polyfunctional amines as initiators. Primary amines supported on resins also readily react with lactide, and this has been applied to remove unreacted monomer from PLA samples without affecting the polymer properties.