Construction of pyridinium/N-chloramine polysiloxane on cellulose for synergistic biocidal application

Cotton cellulose was modified with polysiloxane with dual antimicrobial groups of pyridinium and N-chloramine (N-Cl) to endorse enhanced synergistic biocidal ability. A new compound, 4-oxo-N-(pyridin-4-yl)pentanamide (OPPA), that contains precursors of both pyridinium and N-chloramine was synthesized via amidation of 4-oxopentanoic acid and 4-aminopyridine. The molecules of OPPA were connected to cotton cellulose using poly(methylhydrosiloxane) (PMHS) as linker through hydrosilylation reaction between some Si–H groups of PMHS and hydroxyl groups of cellulose and some other Si–H groups and ketone carbonyl groups of OPPA. The OPPA on cellulose was transformed into its biocidal counterpart after quaternization of the pyridine to pyridinium and chlorination of the amide N–H to N-chloramine. The synthetic procedures and modification results were characterized with Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy. The pyridinium/N-chloramine polysiloxane layer on cellulose was estimated to be 77 nm by weight and provided powerful and synergistic antibacterial capacities against model species of Escherichia coli and Staphylococcus aureus. The stability of the polysiloxane modifier layer and the rechargeability of lost chlorine were promising under repeated washing, long-term storage, and UV irradiation. The presented pyridinium/N-chloramine polysiloxane layer showed advantages over many of the current systems containing either cationic salt or N-chloramine due to the synergism.