Synthesis, assembled structure, and chiroptical properties of amino acid-based amphiphilic block copolymers containing carbazole moiety

Novel amphiphilic block copolymers composed of amino acid-based hydrophilic segment and carbazole-containing hydrophobic segment were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. N-Ethyl-3-vinylcarbazole (E3VC) was employed as a carbazole-containing monomer, which can be regarded as a styrene derivative. N-Acryloyl-l-proline methyl ester (A-Pro-OMe) was selected as an amino acid-containing monomer, which is a disubstituted acrylamide with proline moiety in the side chain. Chain extension from poly(A-Pro-OMe) to E3VC could be well controlled under suitable conditions and provided block copolymers with as-designed chain structures and low polydispersities. The block copolymers were also synthesized by RAFT polymerization of A-Pro-OMe using poly(E3VC) as a macro-chain transfer agent (macro-CTA). In both cases, the dithiobenzoate- and dithiocarbamate-terminated CTAs were compared, in terms of the polymerization rate, polydispersity of the product, controlled character, and block efficiency. We investigated the relationship between the ordered structures, optoelectronic and chiroptical properties of the resulting block copolymers, which were evaluated by dynamic light scattering (DLS), UV-vis, fluorescent, and CD measurements.