Synthesis of chiral micelles and nanoparticles from amino acid based monomers using RAFT polymerization

Homopolymers of tbutyl acrylate (PtBuA) and a monosubstituted acrylamide (PAM) having an amino acid moiety in the side chain, N-acryloyl-(L)-phenylalanine methyl ester 1, have been synthesized by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. Diblock copolymers of these homopolymers were also synthesized by chain extending PtBuA with monomer 1 and after modification, using simple acid deprotection chemistries of the acrylate block to afford a poly (acrylic acid) block, an optically active amphiphilic diblock copolymer was isolated. The optically active amphiphilic diblock copolymers, which contain chiral amino acid moieties within the hydrophobic segment, were then self-assembled to afford spherical micelles which were subsequently crosslinked throughout the shell layer to afford robust chiral nanoparticles. The hydrodynamic diameters (Dh) of the block copolymer micelles and nanoparticles were measured by dynamic light scattering (DLS) and the dimensions of the nanoparticles were determined using tapping-mode atomic force microscopy (AFM) and transmission electron microscopy (TEM).