Synthesis of biodegradable and biocompatible ABC triblock copolymers

A facile approach is offered to synthesize well-defined amphiphilic ABC triblock copolymers composed of poly(ethylene glycol) monomethyl ether (MPEO) as A block, poly(L-lysine) (PLLys) as B block, and poly(ε-caprolactone) (PCL) as C block by a combination of ringopening polymerization (ROP) and click reactions. The propargyl-terminated poly(Z-L-lysine)-block-poly(ε- caprolactone) (MPEO-PzLLys-PCL) diblock copolymers were synthesized via the ring-opening polymerization of N^ε-carbobenzoxy-L-lysine N-carboxyanhydride (Z-L-Lys NCA) in DMF at room temperature using propargyl amine as an initiator and the resulting amino-terminated poly(Z-L-lysine) then used in situ as a macroinitiator for the polymerization of ε-caprolactone in the presence of stannous octoate as a catalyst. The triblock copolymers poly(ethylene glycol) monomethyl ether -block-poly(Z-L-lysine)-blockpoly(ε- caprolactone) (MPEO-PzLLys-PCL) were synthesized via the click reaction of the propargyl-terminated PzLLys-PCL and azido-terminated poly(ethylene glycol) monomethyl ether (PEO-N₃) in the presence of CuBr and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) catalyst system. After the removal of Z groups of L-lysine units, amphiphilic and biocompatible ABC triblock copolymers MPEO-PLLys-PCL were obtained. The structural characteristics of these ABC triblock copolymers and corresponding precursors were characterized by NMR, IR, and GPC. These results showed the click reaction was highly effective. Therefore, a facile approach is offered to synthesize amphiphilic and biocompatible ABC triblock copolymers consisting of polyether, polypeptide and polyester.