Synthesis and self-assembly of dendritic-helical block copolypeptides

Abstract

Dendritic-helical diblock copolypeptides, dendritic poly(L-lysine)-b-poly(γ-benzyl-L-glutamate) (PBLG-Lys) were synthesized up to 4th generation of dendritic poly(L-lysine). PBLG was synthesized by conventional ring-opening polymerization of γ-benzyl-L-glutamate-N-carboxyanhydride with heptyl amine as an initiator. The N-terminus of this PBLG was used for further coupling reactions with N_α,N_ε-bis(t-butoxycarbonyl)-L-lysine pentafluorophenylester. These block copolypeptides possess well-defined 3-D structures in solution, and they self-assemble into a fibrous structure via a nanoribbon mechanism in toluene. Amphiphilic block copolypeptides were obtained after deprotecting BOC groups at the periphery of the lysine dendrimer block. Due to the well-defined size and structure of the dendritic lysine block and well-defined α-helical conformation of the PBLG block, the block copolypeptides showed a generation-dependent self-assembly behavior in aqueous solution.