Organocatalytic Copolymerization of Cyclic Lysine Derivative and ε-Caprolactam toward Antibacterial Nylon-6 Polymers

Functional polymers of nylon-6, particularly those with sustained antibacterial functions, have many practical applications. However, the development of functional ε-caprolactam monomers for the subsequent ring-opening copolymerization (ROCOP) formation of these materials remains a challenge. Here we report a t-BuP₄-mediated ROCOP of dimethyl-protected cyclic lysine with ε-caprolactam, followed by quaternization, affording antibacterial nylon-6 polymers bearing quaternary ammonium functionality with high molecular weight (up to 77.4 kDa). The antibacterial nylon-6 polymers exhibited good physical and mechanical properties and strong antimicrobial activities. At 25 mol % quaternary ammonium group incorporation, the nylon-6 polymer demonstrated complete killing of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The results from this study may provide a strategy for the facile preparation of antibacterial nylon-6 polymers to addressing the public health and safety challenges.