Fluorocarbon-assisted surface orientation of N-halamine groups on cellulose in supercritical CO2: An effective and eco-friendly approach for developing higher biocidability

Preferential segregation of N-halamine structure to top surface to better contact with bacteria is demonstrated to be an effective tactic for achievement of higher biocidability. 5-Allylbarbituric acid and its fluorinated derivative, formed by sacrificing a imide hydrogen to tether a 4-perfluorohexylbutyl segment via nucleophilic substitution, were synthesized and separately attached to (50% methylhydrosiloxane)-dimethylsiloxane block copolymer (P(MHS-DMS)) via hydrosilylation. Chlorination of N-H bonds originating from barbituric acid produced two N-halamine polysiloxanes that were interpenetrated into cellulose to form coatings with similar morphology and thickness. Although containing similar to 50% less total content of chlorine than its nonfluorinated counterpart, polysiloxane with fluorinated pendants exerted faster inactivation against Staphylococcus aureus and Escherichia coli due to the orientation of its N-halamine groups on top surface with the assistance of the lowsurface-tension 4-perfluorohexylbutyl segment as verified by depth profiling using angle-dependent X-ray photoelectron spectroscopy (ADXPS). Design biocide with proper surface segregation ability therefore paves a new way for improved antibacterial efficacy. The stability and rechargeability of the biocidability of the coatings are satisfactory under washing cycles, UV irrigation, and storage.