S. D. Worley

Halamine water disinfectants

This review includes a general discussion of N‐halamine compounds which function as biocides in water. Advantages and limitations of the compounds as compared to free chlorine and other disinfectants are presented. The discussion addresses N‐halamines which are, or have been, in commercial use, but special emphasis will be placed upon two new classes of N‐halamine compounds (oxazolidinones and imidazolidinones) which are under intensive study in the laboratories of the authors. These new N‐halamine compounds are considerably more stable in water than previous ones; the factors dictating their enhanced stabilities are discussed. Potential applications for the new compounds are also addressed.

N-halamine biocidal coatings via a layer-by-layer assembly technique.

Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.

Polymeric antimicrobial N-halamine epoxides.

A new N-halamine copolymer has been prepared, characterized, and evaluated for antimicrobial efficacy, stability toward hydrolyses, and stability toward UVA degradation when covalently bound to cellulose fibers. A copolymer of 3-chloro-2-hydroxypropylmethacrylate and glycidyl methacrylate was coated onto cotton, and, after curing, was treated with an aqueous solution containing the potassium salt of 5,5-dimethylhydantoin to form a coating which became antimicrobial upon exposure to househod bleach (sodium hypochlorite). The coating inactivated S. aureus and E. coli O157:H7 within minutes of contact time and was quite stable toward washing and UVA photodegradation.

Novel n-halamine siloxane monomers and polymers for preparing biocidal coatings

SummariesPrecursor N-halamine siloxane monomers and polymers have been prepared for the purpose of functionalising the surfaces of materials in order to render them biocidal upon exposure to oxidative halogen solutions. The biocidal function can be imparted to the N-halamine moiety either before or after siloxane bonding or adhesion to the surface or material. The biocidal surfaces and materials can then be used to inactivate pathogenic micro-organisms such as bacteria, fungi and yeasts, as well as virus particles, which can cause infectious diseases, and those micro-organisms which cause noxious odours and unpleasant colouring such as mildew. Examples of surfaces and materials which can be rendered biocidal with the N-halamine siloxanes include cellulose, synthetic fibres, ceramics, plastics, polyurethanes and metals. Preparation procedures and some biocidal efficacy data on paper, cotton and polyurethane paint are discussed.RésuméDes monomères et des polymères précurseurs à N-halamine siloxane ont été préparés afin de fonctionnaliser la surface des matériaux pour les rendre biocides quand ils sont exposés à des solutions oxydatives à l’halogène. L’addition de la fonction biocide au groupe caractéristique N-halamine peut précéder ou suivre la liaison du siloxane comme elle peut précéder ou suivre l’adhésion à la surface ou au matériau. Les surfaces biocides et les matériaux peuvent alors être utilisées pour inactiver des micro-organismes pathogéniques inactifs tels que les bactéries, les champignons, les levures, et les particules de virus, qui peuvent provoquer des maladies infectieuses, aussi bien que ces microorganismes, tels que la moisissure, qui créent des odeurs nocives et la coloration désagréable. Des exemples de surfaces et de matériaux qui peuvent être traités des N-halamine siloxanes pour les rendre biocides comprennent la cellulose, les fibres synthétiques, les céramiques, les plastiques, les polyuréthanes, et les métaux. Les procédés de préparation et quelques données dans le domaine de l’efficacité biocide sur le papier, le coton, et la peinture polyuréthane sont discutés.ZusammenfassungN-Halaminsiloxanmonomere und -polymere wurden darauf vorbereitel, duch die Aussetzung an oxidierende Halogenlösungen Oberflächen eine disinfizierende Wirkung zu verleihen. Die Biozid-Wirkung kann der N-Halaminhälfte entweder vor oder nach der Bildung der Siloxanverbindung oder nach Auftragung des Anstriches auf eine Oberfläche verliehen werden. Die Biozidwirkung der Oberfläche neutralisiert sowohl Pathogene wie Bakterien, Pilze, Hefen oder Viren, als auch geruchs- und fleckbildende Mikroorganismen wie Schimmelpilze. Zu den Oberflächen, die mit N-Halaminsiloxan-Biozidanstrichen behandelt werden können, gehören Zellulosen, Synthetik-Fasern, Keramik, Plastik, Polyurethane und Metalle. Wir legen ausserdem die Herstellungsmethoden und Daten zur Effektivität der Biozide auf Papier, Baumwolle und Polyurethananstrichen dar.

N-halamine biocidal coatings

Novel N-halamine siloxane and epoxide coatings are described. The coatings can be rendered biocidal by exposure to dilute bleach. Once the bound chlorine is lost from the coatings, it can be regenerated by further exposure to dilute bleach. Synthetic schemes and biocidal efficacy data are presented. The stabilities of the bound chlorine on the surfaces are also addressed. Substrates employed include sand, textiles, and paint. Potential uses for the technology are discussed.

Novel antimicrobial N-halamine polymer coatings generated by emulsion polymerization

A new class of N-halamine polymers has been synthesized. These polymers can be emulsified in water to produce coatings which, once chlorinated, act as contact disinfectants. The surfaces inactivate bacterial organisms efficiently, requiring relatively brief contact times of several minutes. The latexes can be formed by copolymerization of a N-halamine precursor monomer with other monomers in water with the aid of a surfactant, or by chemically grafting the N-halamine precursor monomer onto an emulsified polymer backbone, followed by chlorination.

Antimicrobial N-halamine modified chitosan films

The inherent antimicrobial properties and biodegradability of chitosan make it an ideal candidate for antimicrobial materials. In this study, N-halamine precursor 3-glycidyl-5,5-dimethylhydantoin (GH) was synthesized and bonded onto chitosan by a ring opening reaction between chitosan and GH. The chitosan film modified with the N-halamine precursor could be rendered biocidal after exposure to a dilute household bleach solution. Syntheses routes, characterization data, and antimicrobial test results are presented. The chlorinated films with 2.60 × 10(18) atoms/cm(2) of active chlorine were challenged with Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) and showed good efficacy against these two bacterial species with log reductions of 7.4 and 7.5 within 10 and 5 min of contact time, respectively. These films may serve as potential materials for food packaging and biomedical applications.

N-halamine copolymers for use in antimicrobial paints.

A series of copolymers containing units of a novel hydantoinylacrylamide and the sodium salt of 2-(acrylamido)-2-methylpropanesulfonic acid have been synthesized. The homopolymer of the hydantoinylacrylamide compound was insoluble in water, while the copolymers with the sulfonic acid sodium salt were water-dispersible/soluble, with the solution becoming completely transparent when the feed ratio for the copolymer contained 7 parts of the hydantoin moiety to 3 parts of the sodium sulfonate moiety. The polymers were added into a commercial water-based latex paint, and upon drying, the painted surfaces treated with the water-miscible copolymers were rendered antimicrobial following chlorination with dilute household bleach. The chlorinated homopolymer failed to provide an antimicrobial property for the paint because of its tendency to isolate into aggregates in the paint, while the completely miscible copolymers were capable of 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 5 min of contact time.

Mechanism of photolytic decomposition of N-halamine antimicrobial siloxane coatings.

Generally, antimicrobial N-halamine siloxane coatings can be rehalogenated repetitively upon loss of their biocidal efficacies, a marked advantage over coatings containing other antimicrobial materials. However, the N-halamine materials tend to slowly decompose upon exposure to ultraviolet irradiation as in direct sunlight. In this work the mechanism of photolytic decomposition for the N-halamine siloxanes has been studied using spectroscopic and theoretical methods. It was found that the N-chlorinated coatings slowly decomposed upon UVA irradiation, whereas the unhalogenated coatings did not. Model compound evidence in this work suggests that upon UVA irradiation, the N-Cl bond dissociates homolytically, followed by a Cl radical migration to the alkyl side chain connected to the siloxane tethering group. An alpha and/or beta scission then occurs causing partial loss of the biocidal moiety from the surface of the coated material, thus precluding complete rechlorination. NMR, FTIR, GCMS, and computations at the DFT (U)B3LYP/6-311++G(2d,p) level of theory have been employed in reaching this conclusion.

The Stabilities of N−Cl Bonds in Biocidal Materials

N-halamine chemistry has been a research topic of considerable importance in these laboratories for over two decades. N-halamine compounds are useful in preparing biocidal materials. There are three N-Cl moieties available in cyclic N-halamine compounds:  imide, amide, and amine. The stabilities toward the release of free halogen have been experimentally shown to decrease in the order amine > amide > imide. In this work, this generalization has been tested theoretically at the level of B3LYP/6-31+G(d) and using the conductor-like polarizable continuum aqueous solvation model with UAKS cavities. Excellent accord was observed between theory and experiment. It was also found that the imide and amide N-halamine stabilities on hydantoin rings could be reversed with substitution patterns at the 5 position.