An upper limit to the N-halamine to cationic salt ratio for antibacterial action on cellulose

In a synergistic unit of N -halamine and cationic salt, an increased ratio of the N -halamine elicited a higher biocidal efficacy. However, the upper limit to the N -halamine content where the synergism is not impaired because of the diminished role of the cationic salt is still unknown. Herein, 4 N -halamine sites, one more than the current maximum, were combined with 1 cationic salt in a composite unit for the evaluation of the effect of such a ratio on synergism. Briefly, 4-aminopyridine was quaternized with 1-chlorohexane to form a cationic pyridinium. Uramil and the cationic pyridinium were successively bonded to allylsuccinic anhydride via ammonolysis and amidation to form a product with 1 cationic salt and 4 N–H bonds as N -halamine precursors. The allylic C=C of the product subsequently reacted with Si–H of poly(methylhydrosiloxane) via hydrosilylation to prepare a polysiloxane that was interpenetrated into cotton cellulose at 50 °C and 28 MPa in supercritical CO 2 . Chlorination of N–H bonds transformed each polysiloxane pendant to the target composite unit that existed in a 71 nm modification layer on the interpenetrated cotton. Antibacterial tests showed that the designed composite units completely eradicated ~ 10 7  CFU of Staphylococcus aureus and Escherichia coli in 15 min, an efficacy between those of a counterpart with only 4 corresponding N -halamine sites and a reported unit with 1 N -halamine and 1 cationic center under comparable conditions, which suggested that the increase of N -halamine to such a ratio did not further benefit synergism. Evaluations of biocidal stability and rechargeability indicated that the modifier was chemically robust and scCO 2 interpenetration produced a durable connection between the modifier and cellulose. Graphical The alternative text for this image may have been generated using AI.