Functional Polyamides: A Sustainable Access via Lysine Cyclization and Organocatalytic Ring-Opening Polymerization

Functional polyamides are very important polymers that have a variety of valuable applications. However, the effective synthesis of these polymers is still a long-going challenge. Herein, the efficient cyclization of lysine derivative was presented as a universal approach to synthesize epsilon-lactam monomers bearing pendant benzyl-protected hydroxyl, allyloxy, and oligo-ethylene glycol groups. Superbase t-BuP4-catalyzed polymerization could proceed under very mild conditions (e.g., 25 degrees C) compatible with a wide range of functional pendants, affording high molecular weight (up to 47.7 kg/mol) functional polyamides with high monomer conversion (up to 99%). Of importance, the allyloxy groups were stable toward the initiating and propagating species under mild polymerization conditions. Such an allyloxy-functionalized e-lactam and organocatalytic polymerization to well-defined allylated polyamide has not been reported in the literature and allows further incorporation of an unprecedented range of functional groups onto polyamides through the thiol-ene click reaction. The resulting functional polyamides demonstrated variable glass transition temperatures, had minimal cytotoxicity to HeLa cells, and exhibited the ability to form nanostructures in aqueous solution, suggesting their great potential for biomedical applications.