Synthesis and self-assembly of helical polypeptide-random coil amphiphilic diblock copolymer

Abstract

Three amphiphilic rod-coil diblock copolymers, poly(2-ethyl-2-oxazoline-b-/-benzyl-L-glutamate) (PEOz-b-PBLG),G), incorporating the same-length PEOz block length and various lengths of their PBLG blocks, were synthesized through a combining of living cationic and N-carboxyanhydride (NCA) ring-opening polymerizations. In the bulk, these block copolymers display thermotropic liquid crystalline behavior. The self-assembled aggregates that formed from these diblock copolymers in aqueous solution exhibited morphologies that differed from those obtained in alpha-helicogenic solvents, that is, solvents in which the PBLG blocks adopt rigid alpha-helix conformations. In aqueous solution, the block copolymers self-assembled into spherical micelles and vesicular aggregates because of their amphiphilic structures. In helicogenic solvents (in this case, toluene and benzyl alcohol), the PEOz-b-PBLG copolymers exhibited rod-coil chain properties, which result in a diverse array of aggregate morphologies (spheres, vesicles, ribbons, and tube nanostructures) and thermoreversible gelation behavior. (C) 2008 Wiley Periodicals, Inc.