Preparation and Application of Regenerable N-Halamine Biocidal Materials

Abstract

Copolymers of an N-halamine siloxane and a quaternary ammonium salt siloxane were prepared using 5,5-dimethylhydantoin and trimethylamine as functional groups. The solubility of this siloxane copolymer in water was dramatically better than that of the hydantoinyl siloxane homopolymer reported previously. The stability of the oxidative chlorine loading on cotton swatches was not affected by the presence of the very hydrophilic quaternary functional group. Utilizing the new copolymer in an antimicrobial coating application offers the advantage that no organic solvent is required when preparing a coating bath for textile materials because copolymer is adequately soluble in water whereas most siloxanes are only soluble in organic solvent. The monomers of the compounds 6-phenyl-3-(3’-triethoxysilylpropyl)-1,3,5- triazinane-2,4-dione and 6,6-dimethyl-3-(3’-triethoxysilylpropyl)-1,3,5-triazinane-2, 4-dione were synthesized and coated on the surfaces of silica gel particles and cellulose. Exposure to diluted sodium hypochlorite solutions rendered these polymers antimicrobial. The treated polymers inactivated 7 log concentrations of both Staphylococcus aureus and Escherichia coli O157:H7 with brief contact times. The coated cotton fabrics showed great stability and rechargeability following exposure to UV and ambient light. Several functionalized N-halamine monomers were synthesized for this study, namely 5-aminomethyl-5-methyl-hydantoin, 5-methyl-5-hydroxylmethylhydantoin, and 5-chlormethyl-5-methylhydantoin. The first two of theses N-halamine precursors can be coated onto cotton surfaces with the addition of the cross-linking agent butanetetracarboxylic acid (BTCA), and 5-chlormethyl-5-methylhydantoin can also be coated onto cotton surfaces with the aid of sodium hydroxide as a catalyst. All of these treated cotton swatches were rendered biocidal by exposure to halogen solutions either before or after curing the coating or material. The preparation of several new hydantoin diols and tetraols is also reported here. These were copolymerized with commercial polyol and diisocyanate to form different polyurethane films that could be painted onto a surface. Activation by chlorination produced biocidal polyurethane films.