Bactericidal silicone with one quaternary ammonium salt and two N-halamine sites in the repeating unit for improved biocidability on magnetic submicrospheres

This study proves that the attraction of anionic bacteria by a cationic center to its neighboring N-halamine sites is a tactic for the design of bactericidal polymers with super biocidability. A silicone containing one cationic quaternary ammonium salt (QAS) and two imide N-halamine sites in the repeating unit was developed on SiO2/Fe3O4 submicrospheres for better antibacterial performance, larger bactericidal area and easier recyclability. Briefly, the product of nucleophilic substitution of diethyl malonate by 3-chloro-1-(N,N-dimethyl)propylamine was ammonolyzed with urea to synthesize 5-(3-(N,N-dimethyl)propyl)barbituric acid whose tertiary amine was subsequently quaternized with (3-chloropropyl) trimethoxysilane. The quaternized molecules were hydrolyzed and polymerized into a silicone layer on SiO2/Fe3O4 submicrospheres. Chlorination of the two imide N-H bonds of barbituric acid ring finalized the synthesis of the bactericidal silicone. Antibacterial tests verified that the biocidability of the integration of one QAS and two N-halamine sites was more powerful than not only non-synergistic mono-functionality but also reported combination of one QAS and one N-halamine, demonstrating that the increase in the ratio of N-halamine to QAS can generate improved biocidability. Besides, the silicone showed satisfactory biocidal stability and rechargeability.