Quaternized Nylon-6 Polymers via Ring-Opening Polymerization of Cyclic Lysine Derivatives: A Versatile Antibacterial Platform

Nylon-6, while commercially essential, has proven challenging to endow with persistent antibacterial properties due to the lack of efficient and facile synthetic approaches. Poly(ε-lysine) derivatives have attracted considerable research attention due to their structural backbone similarity to that of nylon-6. Capitalizing on this structural similarity, herein, we achieved hydrophobicity-tunable quaternized nylon-6 polymers through rational design of side-chain structures in lysine-derived cyclic monomers and controlled quaternization reactions. By precisely controlling the quaternization process, amphiphilic quaternized nylon-6 polymers with adjustable hydrophobicity and cationic charge density were successfully prepared, enabling systematic evaluation of their broad-spectrum antimicrobial properties. Notably, enhanced hydrophobicity was found to significantly improve antibacterial efficacy against both Escherichia coli and its biofilms, with the amphiphilic polymers demonstrating superior antimicrobial performance. Furthermore, these amphiphilic quaternized nylon-6 polymers exhibited a thermoresponsive behavior. This work proposes a new design strategy for antimicrobial nylon-6 polymers, enabling the simultaneous enhancement of antibacterial functionality and the incorporation of temperature-responsive properties.