Biofunctionalization of poly(ethylene terephthalate) (PET) is crucial to its medical and biomedical
applications such as surgical drapes, vascular grafts and ligament prostheses. To furnish PET with an alkynyl
handle, N-(2-methylbut-3-yn-2-yl)acrylamide (MBAA) underwent photo-initiated copolymerization with
N,N-methylenebisacrylamide (MBA) in methanol-swollen PET surface to form a 3-dimensional interpenetrating network
(IPN). The alkynyl handle terminated surface was denoted as PMBAA-PET. A region-selective modification could be
achieved using an engraved mask during the photo-initiated copolymerization.

We previously reported that covalently joining an amide-based N-chloramine with a quaternary ammonium
compound (QAC) can yield a new composite biocide with faster inactivation of various bacteria. Importantly, the
composite biocide was found to reduce the risk for potential bacterial resistance associated with QAC. However,
similar to other N-chloramines and QACs, this high-performance composite biocide becomes less potent against
pathogenic bacteria in the presence of high protein fluids. In this study, we substituted the amide-based
N-chloramine moiety in the previously reported composite biocide with a secondary amine-based N-chloramine to
improve the biocidal efficacy in biological fluids. The N–Cl bond in the synthesized tetramethylpiperidine-based
composite biocides is more stable in a high protein medium (HPM) than that in the hydantoin (amide)-based composite
biocides. The composite biocide,
2-[4-(1-chloro-2,2,6,6-tetramethyl-piperidin-4-yloxymethyl)-[1,2,3]triazol-1-yl]-ethyl-dodecyl-dimethyl-ammonium
chloride (6a), showed the best antibacterial activity in both phosphate-buffered saline and HPM among various
composite biocides and benzyldodecyldimethylammonium chloride used in this study.