A Simple Post-Polymerization Modification Method for Controlling Side-Chain Information in Digital Polymers

International audienceA three-step post-polymerization modification procedure was studied for the design of digitally-encoded poly(phosphodiester)s with controllable side-groups. Sequence-defined precursors were synthesized, either manually on polystyrene resins or automatically on controlled pore glass supports, using two phosphoramidite monomers containing either terminal alkynes or triisopropylsilyl (TIPS)-protected alkyne side-groups. Afterwards, these polymers were modified by stepwise copper-catalyzed azide-alkyne cycloaddition (CuAAC). The terminal alkynes were first reacted with a model azide compound and, after deprotection of the TIPS groups, the remaining alkynes were reacted with another organic azide. This simple method allows quantitative side-chain modification, thus opening up interesting avenues for the preparation of a wide variety of digital polymers. Yet, optimized protocols reported herein shall be followed. For instance, the use of iodine in iterative phosphoramidite chemistry may result in the formation of unwished iodo-acetylenes. Practical solutions to bypass that problem are reported herein