Tetrazine-norbornene click reactions to functionalize degradable polymers derived from lactidea

Post-polymerization modification of polymers derived from sustainable resources using the click reaction between tetrazines and norbornenes is shown to provide a mild and efficient route for the synthesis of functional degradable polymers. Norbornene chain-end functional poly(lactide) was synthesized using organocatalytic methods and functionalized by the addition of 3,6-di-2-pyridyl-1,2,4,5-tetrazine without degradation of the polymer backbone. The versatility of this reaction was demonstrated by the application of analogues bearing amine and poly(ethylene oxide) groups to realize aminefunctional polymers and block copolymers. Poly- (spiro[6-methyl-1,4- dioxane-2,5-dione-3,20-bicyclo- [2.2.1]hept[5]ene]) was prepared from lactide. The pendant norbornene group on the backbone of the resultant polymer was modified in a similar manner to produce functional degradable polymers and graft co-polymers.