Stabilization of Amino Acid Derived Diblock Copolymer Micelles through Favorable D:L side chain interactions

Optically pure N-acryloyl-(D)-leucine methyl ester (d-Leu-OMe) (1) and N-acryloyl-(L)-leucine methyl ester (l-Leu-OMe) (2) were synthesized and studied using infrared spectroscopy and melting point analysis to determine if d−l interactions are preferential relative to d−d or l−l interactions. Reversible addition−fragmentation chain transfer (RAFT) polymerization yielded enantiopure homopolymers of d-Leu-OMe (1) and l-Leu-OMe ester (2). The two enantiopure polymers, 5 and 6, and a 1:1 w/w racemic blend of both polymers were studied using infrared spectroscopy to investigate the intermolecular interactions in the polymeric systems. Poly(tert-butyl acrylate) [P(tBuA)] macro chain transfer agents were used to synthesize two diblock copolymers from 1 and 2, respectively. Subsequent deprotection of the P(tBuA) block to poly(acrylic acid) (PAA) yielded two chiral amphiphilic diblock copolymers, 7 and 8. Both enantiopure polymers were self-assembled separately and then in a 1:1 w/w ratio, and the resulting morphologies characterized using dynamic light scattering, atomic force microscopy, transmission electron microscopy, and circular dichroism.