Phototriggered Ring-Opening Polymerization of a Photocaged l-Lysine -Carboxyanhydride to Synthesize Hyperbranched and Linear Polypeptides.

Increasing efforts are being made on controlled photopolymerization methodologies; however, the previous polymerization systems need additional photoactive initiators or catalysts. The controlled synthesis of the hyperbranched polypeptide is still challenging, and developing a photopolymerization method to prepare a hyperbranched polypeptide is urgent for constructing biodegradable polymers and biomaterials. Without addition of any initiator/catalyst, we combine the inimer (initiator + monomer) ring-opening polymerization (ROP) and photocaged chemistry to prepare hyperbranched and linear polypeptides. The photocaged Nε-(-nitrobenzyloxycarbonyl)-l-lysine--carboxyanhydride possesses intrinsic photosensitivity and will be transformed into an activated AB* inimer-type α-amino acid -carboxyanhydride (NCA) containing a primary ε-amine, which further triggers ROP to produce linear and/or hyperbranched polypeptides in one pot and at room temperature. The microstructure and topology of the resulting polypeptide were clarified by means of mass spectroscopy and various NMR techniques including H NMR, H, H-COSY, and quantitative C NMR. By tuning the UV irradiation time or intensity, this methodology can produce a linear polypeptide with a high of 109 kDa and/or (hyper)branched counterparts with tunable 's of 1.4-73.5 kDa and degree of branching of 0.09-0.60.