The ring-opening polymerization (ROP) of amino acid N-carboxyanhydrates (NCA) gives rise to a broad range of synthetic polypeptides. While this process is known since the 1960s, the last decade has seen a significantly increased interest in this polymerization due to the fact that synthetic polypeptide are simplistic peptidomimetics with high potential as biomaterials. Reported examples include amphiphilic block copolymers for self-assembly into nanostructures, surface grafted polypeptides as well as complex polypeptide architectures and bioconjugates. Advances in the NCA polymerization process have facilitated the synthesis of well-defined polymer structures either by classical primary amine (nucleophile) initiation or transition metal mediated processes. An approach that has not been achieved to date is light induced initiation of NCAs. Here we report the first example of UV-initiated polymerization of NCAs. Special emphasis of this work was the demonstration that the initiation process is selective and that the polymers are structurally well-controlled. Initiation was achieved by photogeneration of the initiating secondary amine species from a photobase generator in the presence of NCA. Real-time FTIR confirmed the formation of polypeptide only in the presence of UV-light and photoinitiator, while in their absence no polymer was formed. Detailed MALDI-ToF-MS analysis proved the presence of the amine initiator as the polymer endgroup, highlighting its active role in the initiation process by the Normal Amine Mechanism (NAM).

Light-induced polyerization of N-carboxyanhydrides (NCA)

252nd National Meeting (2016)

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