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The surfaces of materials fabricated from stainless steel are challenging to functionalize with antimicrobial moieties. This work demonstrates that stainless steel surfaces can be modified with an N-halamine-based copolymer in order to obtain antimicrobial activity. In this regard, a copolymer (HACM) of 2-acrylamido-2-methyl-1-(5-methylhydantoinyl)propane and 3-cloro-2-hydroxypropyl methacrylate was synthesized and grafted onto a stainless steel surface via covalent attachment. Synthesized monomers and copolymers were characterized by NMR, FTIR, and XPS spectral analyses. Upon treatment with dilute bleach, the stainless steel surfaces were rendered antimicrobial, possessing a sufficient amount of chlorine content and excellent stability and durability. The modified stainless steel samples inactivated 6 logs of Staphylococcus aureus and Escherichia coli O157:H7 bacteria within 15 min of contact time. Stabilities of the coatings toward washing and UVA exposure were also studied. The stainless steel samples ...

Disinfecting, nonbleaching compound 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) was uniformly coated onto polypropylene melt-blown nonwoven fabrics having basis-weights of 22 and 50 g/m(2) in order to impart antimicrobial properties via a pad-dry technique. The antimicrobial efficacies of the tested fabrics loaded with MC compound were evaluated against bioaerosols of Staphylococcus aureus and Escherichia coli O157:H7 utilizing a colony counting method. It was determined that both types of coated fabrics exhibited superior antimicrobial efficacy upon exposure to aerosol generation for 3 h. The effect of the coating on air permeability was found to be minimal. Samples were stable for a 6 month time period when they were stored in darkness. However, when the fabrics were exposed to fluorescent light, partial chlorine loss was observed. The MC-coated fabrics exhibited great potential for use in protective face masks and air filters to combat airborne pathogens.

Anionic and cationic N-halamine polyelectrolytes were synthesized, characterized and then immobilized onto melt-blown polypropylene fabrics having two different basis-weights. The coatings were rendered biocidal upon exposure to dilute sodium hypochlorite solution. The effect of single and multilayer deposition of the polyelectrolytes on the surfaces was investigated in terms of chlorine loadings, rechargeabilities, antimicrobial efficacies, and air permeabilities. It was found that all of the coatings provided remarkable biocidal efficacies with about six log reductions of bacteria within two min of contact time on filters having higher basis-weight, whereas slower inactivation was observed for lower-basis weight filters due to diminished surface areas and numbers of active halogen atoms. The antimicrobial coatings reduced the air permeabilities of the filters somewhat; however, the air permeabilities of the coated swatches were comparable to those of most protective textiles.

A novel macroporous cross-linked antimicrobial resin containing quaternarized N-halamine groups, poly(1-chloro-5,5-dimethylhydantoinyl-3-ethyl-p-ethenylphenylmethyl dimethylammonium chloride) (Cl-PSQH), has been synthesized by a facile three-step reaction. The as-prepared resins were characterized by FT-IR, X-ray photoelectron spectroscopy, and zeta-potential measurement. Antimicrobial tests showed that Cl-PSQH was capable of about a 7-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 1 min of contact. Also, its regenerability and preliminary storage stability were investigated.

A new hydantoin-containing N-halamine homopolymer was synthesized and characterized. The polymer was coated onto polyethylene terephthalate (PET) and PET/cotton fabric by a pad-dry procedure, and the coated fabrics were rendered biocidal by exposure to dilute household bleach. The chlorinated fabrics inactivated about six logs of Staphylococcus aureus and Escherichia coil O157:H7 within 30-60 min of contact time. The coatings on both surfaces were rechargeable and exhibited adequate stabilities toward washing and UVA light exposure. It was found that the coatings provided superior UVA light stabilities on PET surfaces; whereas, more rapid biocidal activity was observed for the PET/cotton fabrics. (C) 2013 Elsevier B.V. All rights reserved.

The outstanding advantages of N-halamine materials over other antimicrobial materials are their durable and rechargeable antimicrobial properties, as well as their efficacies in inactivating a broad spectrum of pathogens. Theoretically, the oxidative chlorine of antimicrobial cotton coated with N-halamine hydantoin diol can be restored upon loss of its biocidal efficacy after exposure to ultraviolet light. In this work nano-titania particles were added into the coating solutions containing N-halamine diol and 1,2,3,4-butanetetracarboxylic acid (BTCA), and the coatings were applied to produce antimicrobial cellulose with improved UV stability. The treated cotton fabrics were characterized by FT-IR, SEM, XRD, and XPS. The effects of the coatings on tensile strength and wrinkle recovery angle were investigated. Biocidal efficacies of fabrics coated with hydantoin diol and diol/TiO2 against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) were determined using a modified AATCC 100-1999 method and showed excellent antimicrobial properties against these two bacterial species within a brief contact times. It was found that the addition of Nano-TiO2 in the antimicrobial coatings, especially rutile titanium dioxide, could improve the UV light stability of the chlorinated fabrics coated with hydantoin diol significantly. The UV light stability of N-halamine coatings were enhanced with increasing amounts of rutile TiO2.

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.

A novel heterocyclic N-halamine acetate homopolymer was synthesized and characterized by ATR-IR, NMR and MALDI-TOF spectroscopy and TGA and DSC analysis. The homopolymer was coated onto poly(lactic acid) (PLA) meltblown nonwoven fabric, and the surfaces were rendered biocidal upon exposure to dilute sodium hypochlorite solution. The coatings were quite stable versus UVA and florescent light exposure. Moreover, they exhibited long-term shelf-life stability, and they were rechargeable when oxidative chlorine on the surfaces was partially exhausted after three months storage. It was found that the chlorinated fabrics exhibited effective antimicrobial activity with about six logs inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 30 min of contact time. The coated PLA possesses potential for use in antimicrobial food packaging, filters, and hygiene products.

N-(hydroxymethyl) acrylamide (NMA) was immobilized on cotton surfaces through etherification, and then methacryla- mide (MA) was grafted onto the treated surface. The coatings were characterized by ATR-IR spectroscopy and were rendered biocidal upon exposure to dilute household bleach. The treated fabrics were challenged with Gram-negative and Gram-positive bacteria; both NMA and NMA/MA-treated fabrics inactivated about 8 logs of Escherichia coli O157:H7 and Staphylococcus aureus within only 5 min of contact time. The coatings were also quite stable toward ultraviolet (UVA) light exposure and repeated laundering. More- over, a substantial improvement in wrinkle recovery angle was obtained for the NMA/MA-treated fabrics. The new acyclic acrylamide N-halamine coating should be less expensive to produce and use than previous cyclic N-halamine coatings developed in these labora- tories. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 4405-4410, 2013

A vinyl N-halamine acrylamide monomer was copolymerized with silane-, epoxide-, and hydroxyl group-containing monomers. The resultant copolymers were coated onto cotton fabric through hydrolysis of alkoxy groups with formation of silyl ether bonding, opening of the epoxide ring and subsequent reaction with hydroxyl groups on cellulose, and by crosslinking between the hydroxyl groups on the copolymer and on cellulose, respectively. The coatings were rendered biocidal upon exposure to dilute household bleach solution. All of the coatings provided complete inactivation of about six log of Staphylococcus aureus and Escherichia coli O157:H7 within minutes of contact time. The effects of the aforementioned tethering groups on wash fastness and ultraviolet light exposure were also studied.

The antimicrobial compounds 1-chloro-3,5,5-trimethylhydantoin and 3-chloro-1,5,5-trimethylhydantoin (1 and 2, respectively) have been synthesized and examined via a joint experimental and computational study. The measured rate of loss of oxidative chlorine in the absence and presence of exposure to UVA irradiation determined 2 to be less stable than 1. An interesting migration reaction was observed during UVA irradiation that featured the production of chlorine rearrangement and dechlorinated compounds. Two novel hydrogen atom transfer reaction (HATR) mechanisms have been proposed: (1) an intramolecular process in which a hydrogen atom undergoes a series of sigmatropic shifts, and (2) an intermolecular pathway in which a radical abstracts a hydrogen atom from a neighboring molecule. Density functional theory (DFT) calculations at the UB3LYP/6-311G++(2d,p) theory level have been employed to elucidate the preferred reaction pathway. Both proposed HATR mechanisms predicted 2 to possess a lower free energy of activation, ΔG(‡), relative to 1 in accordance with the experimental stability measurements. However, the intermolecular route had an overall lower absolute ΔG(‡) and was more consistent with measured product ratios in solution. The intermolecular reaction pathway, unlike the intramolecular route, also predicted the lack of formation of a migration product featuring a Cl covalently bonded to a methylene group at the 5-position of the hydantoin moiety, which was verified by NMR experiments.

To achieve biocidal properties, a cyclic N-halamine precursor, 7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]-decane-2,4-dione (TTDD), was synthesized and introduced into nanosized polyacrylonitrile fibrous mat by an electrospinning technique. It was rendered antimicrobial by exposure to dilute hypochlorite solution. Synthesis routes and characterization data are presented. Scanning electron microscopy (SEM) demonstrated that the ultrafine fiber possessed average diameter 414 nm (from 240 to 650 nm). The chlorinated nanofibrous composites provided about 4.9 log reductions of both Gram-positive bacteria Staphylococcus aureus (ATCC 6538) and Gram-negative bacteria Escherichia coli O157:H7 (ATCC 43895) within 5 min of contact time. This is indicative of promising possible applications in the filtration of water and air. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Three heterocyclic N-halamine structures containing amine, amide, or both functional groups were immobilized onto cotton fabric through epoxide tethering. The coatings were rendered biocidal upon exposure to dilute household bleach solution. The coatings exhibited superior biocidal functionality with complete inactivation of about 6 logs of Staphylococcus aureus and Escherichia coli O157:H7 within 2–10 min contact time depending on the structure. Moreover, the coatings were quite stable against repeated laundering so that recharging was not even necessary after 50 washing cycles. Stability of the coatings against ultraviolet light exposure was studied with a comparison of the amide- and amine-containing N-halamines.

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.

The composite fibers of cellulose, starch, and a commercial hindered amine light stabilizer have been produced in various concentrations of the components using 1-butyl-3-methylimidazolium chloride as the spinning solvent in order to evaluate their physical properties. The composite fibers allowed desirable properties of both polymers to be retained, while producing fibers of reasonable physical properties. The halogenated hindered amine light stabilizer exhibited remarkably good resistance towards repeated ultraviolet light irradiation and halogenation cycles.

A new N-halamine acrylamide monomer having 31 wt.% chlorine loading capability was synthesized and then copolymerized with a tethering siloxane monomer in several feed ratios. The resulting copolymers were coated onto cotton fabric and rendered biocidal upon treatment with 1% household bleach. The halogenated coated fabrics provided a total of 8-logs inactivation of both Gram-negative and Gram-positive bacteria within 5 min of contact time. The equimolar and siloxane-rich copolymers were noticeably stable on cotton fabric toward washing cycles, as only 10% of the copolymers were hydrolyzed from the cotton surface after the equivalent of 50 machine washes. The halogenated coated fabrics lost about half of the chlorine slowly within 24 h under UVA light irradiation with some decomposition observed.

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.

Phenyl substitution at position 5 on the hydantoin ring of a series of N-halamine derivatives, including an antimicrobial siloxane used for coating surfaces, has been employed to better understand the biocidal activities and stabilities of these compounds in the presence of water and exposure to ultraviolet irradiation. This phenyl derivatization of the hydantoin ring at its 5 position does, in fact, affect the antimicrobial efficacy of the siloxane against Staphylococcus aureus and Escherichia coli O157:H7, and its stability toward hydrolyses and ultraviolet light exposure. The phenyl substitution caused weakening of the N-Cl bond at the 1 position on the hydantoin ring, leading to an increase in biocidal activity but a decrease in stability. Model compounds were studied experimentally and theoretically at the (U)B3LYP/6-311++G(2d,p) level of theory in order to better explain the observations. It was found that the phenyl moiety at position 5 on the hydantoin ring can interact with the oxidative chlorine atom bonded to the amide nitrogen atom at position 1 which then results in a less stable N-Cl bond.

Low concentrations of acyclic amide monomers, methacrylamide (MAM) and acrylamide (AM), were copolymerized with vinyl acetate (VAc). No significant differences between the synthesized copolymers and poly(VAc) were seen by 1H-NMR, FTIR, and DSC analysis. Biocidal films, formed by coating the copolymers onto polyester transparency slides and polyester fabric swatches, were chlorinated by exposure to sodium hypochlorite solutions. Both S. aureus and E. coli O157: H7 were completely inactivated within 1 min on the transparency slides and polyester fabric swatches derived from poly(VAc-co-MAM). The chlorine on the films was stable under UVA irradiation and the surfaces were rechargeable upon chlorine loss.

An N-halamine precursor, 3-(5'-methyl-5'-hydantoinyl)acetanilide (I), was synthesized in our laboratory and loaded onto electrospun polyacrylonitrile fiber to prepare nanosized biocidal materials, which could be rendered antimicrobial by exposure to household bleach. Differential scanning calorimetry was used to study the thermal properties of the nanofibers with and without the N-halamine precursor and its chlorinated derivative loaded. Scanning electron microscopy demonstrated that the ultrafine fibers formed with diameters from 250 to 600 nm. Chlorinated nanofibrous mats composed of the fibers were challenged with Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895); they showed promising inactivation efficacies against the two bacterial species within 5 minutes of contact. Potential uses of the antimicrobial fibers include filters for industrial water and air disinfection and protective clothing.

A new N -halamine precursor, 3-(2,3-dihydroxypropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD diol), was synthesized and bonded onto cotton fabrics. Fabrics with variable amounts of chlorine loading were prepared by using several concentrations of TTDD diol. A second N -halamine precursor, 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD siloxane), was also synthesized and bound to cotton for comparison purposes. The coated cotton fabrics contained two types of N–Cl moieties after chlorination of the amine and amide groups. Swatches with variable chlorine loadings were challenged with Staphylococcus aureus and Escherichia coli O157:H7 as a function of contact time. The biocidal test results showed that the chlorine loadings and surface hydrophobicities influenced the antimicrobial efficacies. The chlorinated swatches have also been employed to oxidize the simulant of chemical mustard to the less toxic sulfoxide derivative.

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 have been synthesized and coated on the surfaces of silica gel particles and cellulose. Exposure to diluted sodium hypochlorite solutions renders these polymers antimicrobial. The treated polymers inactivated (7 logs) 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.

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 improved over that of a hydantoinyl siloxane homopolymer developed earlier. The biocidal activity of cotton swatches coated with the copolymer was evaluated against S. aureus and E. coli O157:H7; the antimicrobial fabric with 0.23%−0.26% chlorine loading could inactivate 107 colony forming units (CFU) of bacteria within 1−5 min of contact. It was observed that a 1 wt % coating bath could provide a coating that could be chlorinated to greater than a 0.20% chlorine loading for a copolymer having a 9:1 ratio of hydantoin to quat moieties. The stability of the oxidative chlorine loading on the cotton swatches was not affected by the presence of the very hydrophilic quat functional group. Use of the copolymer in an antimicrobial coating application will be desirable because no organic s...

An N-halamine precursor containing two hydroxyl groups (diol) has been synthesized. The N-halamine diol precursor was coated onto cotton fabrics with the assistance of the cross-linking agent BTCA. The surface of the coated cotton could be rendered biocidal by exposure to dilute hypochlorite solutions. Syntheses routes, characterization data, and antimicrobial test results will be presented. The durability and rechargeability of chlorine on the coated cotton was determined according to an AATCC standard washing test. The chlorinated cotton swatches were challenged with Staphylococcus aureus ( ATCC 6538 ) and Escherichia coli O157:H7 ( ATCC 43895 ) and showed excellent efficacy against these two bacterial species within a brief time of contact. Over 70% of the chlorine lost after repeated washing or UVA irradiation could be regained upon rechlorination.

The N-halamine monomer 3-(4'-vinylbenzyl)-5,5-dimethylhydantoin (VBDMH) was synthesized and employed to form thin films on the surfaces of polyester fibers by surface polymerization with the aid of a cationic surfactant. The coated samples were characterized by FTIR and SEM. The thin film coatings could be rendered biocidal by exposure to dilute sodium hypochlorite. The antimicrobial polyesters were challenged with Staphylococcus aureus and Escherichia coli O157:H7. Complete inactivation of S. aureus and E. coli O157:H7 was observed within 10 and 30 min of contact time, respectively. The chlorine bonded to the coatings was very stable under standard washing tests and UVA irradiation tests, and much of the lost chlorine could be regenerated by rechlorination.

Variation of alkyl substitution at position 5 on the hydantoin ring of a series of N-halamine siloxane derivatives has been employed to better understand the biocidal activities of these compounds for use in preparing antimicrobial coatings. The alkyl derivatization of the hydantoin ring at its 5 position, while an essentially constant chlorine loading is maintained at the 1 position, has shown that there is little dependence of the antimicrobial efficacy against Escherichia coli O157:H7 on the alkyl chain length, in contrast to reported observations for biocidal quaternary ammonium salt derivatives. The stabilities of the derivatives toward hydrolyses and ultraviolet light exposure have also been found to not be dependent upon the nature of the alkyl substituent group. These observations led to the conclusion that the 5,5-dimethyl derivative would be recommended for use, since it is the least expensive alternative.

The monomer 3-(4′-vinylbenzyl)-5,5-dimethylhydantoin (VBDMH) was synthesized and used to coat cotton fibers by admicellar polymerization using a cationic surfactant. The coated thin-film on cotton was characterized by FTIR and SEM. After chlorination with dilute sodium hypochlorite, the polymeric-coated cotton fabrics effectively inactivated both Staphylococcus aureus and Escherichia coli O157:H7 in relatively brief contact times. The stability and rechargeability of the coated cotton fabrics were very good as evidenced by standard washing tests.

N-halamine silane syntheses and coatings of cotton fabrics as siloxanes were addressed for a series of silanes. The coated fabrics were chlorinated by exposure to dilute sodium hypochlorite with a range of chlorine loadings from 0.20% to 0.26%. Two types of N–Cl moieties were involved in the N-halamine siloxanes, amine and amide. The siloxane-coated cotton swatches were very effective in inactivating Escherichia coli O157:H7 and Staphylococcus aureus, each in 10 min contact time. The N–Cl bond and compound stabilities under UV irradiation and ambient light exposure were also investigated. Both UV and laboratory light stability tests show that most of the chlorine on cotton coated with 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione could be regenerated after irradiation, while most of the lost chlorine from 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin and 4-[3-triethoxysilylpropoxyl]-2,2,6,6-tetramethylpiperidine could not be recovered upon rechlorination.

The hydantoin moiety is an important pharmacore, and when halogenated, hydantoin derivatives act as excellent biocides. However, there have been no computational studies concerning the chlorination mechanism for the hydantoin moiety reported. Herein we describe a computational mechanistic study of the chlorination of 5,5-dimethylhydantoin (H) at the B3LYP/6-311+G(2d,p) level. Under a 1:1 molar ratio of hydantoin and a chlorinating agent (HOCl), conproportionation is calculated to be favorable to give the N1 monochloro derivative as the major predicted product, which is in agreement with experiment. Initial direct chlorination at the N1 position is prevented by a high kinetic barrier. The first step involves the deprotonation of the hydantoin moiety (at the N3 position) which is followed by a SN2 step transferring a chloronium ion (Cl(+)) from HOCl to the ionized hydantoin anion. A mechanism is proposed where the N3 nitrogen is chlorinated first followed by the N1 position to form the dichloro derivative. When CPCM solvation free energies (ΔG(solv)) were added to the gas-phase free energies (ΔG(gas)) along the SN2 reaction path, a sudden decrease in free energy was observed due to the incipient formation of the hydroxide ion. Explicit consideration of solvation within a box of 512 water molecules led to a much more gradual free energy change along the reaction path but a very similar free energy of activation.

A series of new N-halamine epoxide precursors, 3-glycidyl-5,5-dialkylhydantoins (GH's), has been synthesized by a very facile and economic method. Cellulose surfaces can be treated with GH's and re...

An N-halamine precursor, m-aminophenyl hydantoin ( m-APH), which was rendered antimicrobial through exposure to chlorine bleach, was synthesized and was applied on cotton fabric using polycarboxylic acids as crosslinking agents. Particularly, 1,2,3,4-butanetetracarboxylic acid (BTCA) with m-APH treated cotton fabric resulted in the highest increased wrinkle recovery angle and chlorine content simultaneously. Durability and rechargeability were measured through an AATCC test method and antimicrobial efficacy of BTCA/ m-APH treated cotton fabric against Gram-positive and Gram-negative bacteria showed a 6 log reduction within 1 min of contact time.

N-halamine chemistry has been an important research topic in these laboratories for over two decades, offering many exciting opportunities both from practical and pedagogical points of view. One of these opportunities is in the use of polymer- and silica gel-bound N-halamines as selective oxidizing agents for organosulfur compounds. In this study, they have been employed to selectively oxidize organic sulfides including dimethyl sulfide and chloroethyl ethyl sulfide, the chemical mustard stimulant. The latter oxidation produced the less toxic sulfoxide derivative with about 70% conversion, with no sulfone produced, and only about 30% accompanying conversion to sulfoxide hydrolysis products. In this article, we report a combination of experimental and computational results.

Kevlar and Nomex are high-performance polymers which have wide varieties of applications in daily life. Recently, they have been proposed to be biocidal materials when reacted with household bleach (sodium hypochlorite solution) because they contain amide moieties which can be chlorinated to generate biocidal N-halamine functional groups. Although Nomex can be chlorinated without any significant decomposition, Kevlar decomposes under the same chlorination conditions. In this study, two mimics for each of the polymers were synthesized to simulate the carboxylate and diaminophenylene components of the materials. It was found that the p-diaminophenylene component of the Kevlar mimic is oxidized to a quinone-type structure upon treatment with hypochlorous acid, which then decomposes. However, such a mechanism for the Nomex mimic is not possible. In this paper, based upon these observations, a plausible answer will be provided to the title question.

N-halamines serve as important antimicrobial agents. Development of this class of compounds has been shown to provide benefits especially from a biocidal point of view. A novels-triazine-basedN-heterocycle, dichloro-m-aminophenyl-hydantoinyl-s-triazine (DAPHT), which could be rendered antimicrobial through exposure to diluted chlorine bleach, was synthesized and characterized by1H NMR,13C NMR, and FT-IR. A finishing method was used to apply theN-halamine precursor onto cotton fabric, and the optimum conditions for finishing were investigated. The DAPHT-treated cotton fabric had durable antimicrobial properties up to 50 standard washing cycles and was rechargeable under normal laundry/bleaching conditions. The antimicrobial efficacy against Gram-positive and Gram-negative bacteria was demonstrated.

The sterically hindered amine monomer 4-[3-triethoxysilylpropoxyl]-2,2,6,6-tetramethylpiperidine has been synthesized and covalently bonded to the surfaces of silica gel particles and cellulose (cotton) and copolymerized in a polyurethane coating formulation. Upon exposure to dilute sodium hypochlorite (household bleach), a very stable N-Cl bond is formed in situ at the hindered amine nitrogen site. This source of oxidative chlorine provides an antimicrobial function to the silica gel, cotton, and polyurethane. Stability, regenerability, and biocidal efficacy data are presented. The new N-halamine materials were remarkably effective against Staphylococcus aureus and Escherichia coli O157 : H7 in brief periods of contact. The materials should find application in water treatment and medical applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

A water dispersible terpolymer of [2-(methacryloyloxy)ethyl]trimethylammonium chloride, glycidyl methacrylate and hydantoinyl acrylamide was synthesized and coated on poly(ethylene terephthalate) fabrics through a pad-dry-cure procedure. The coatings were rendered biocidal upon exposure to dilute household bleach solution. The halogenated fabrics exhibited great antimicrobial functionality with about six logs inactivation of S. aureus and E. coli O157:H7 within only two min of contact time. Moreover, the coatings were found to be very stable against repeated washings and UVA light exposure. It was shown that [2-(methacryloyloxy)ethyl]trimethylammonium monomer is very useful in preparing waterborne N-halamines which can impart rechargeable, effective, and stable antimicrobial coatings to poly(ethylene terephthalate) fabrics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43088.

The demand for protection against biological and chemical warfare agents has increased the need for unique protective materials. N-halamines are superior candidates for this task by having rapid inactivation rates against a broad range of microorganisms and the ability to oxidize some pesticides and warfare agents to reduce their toxicity to humans. Thus, the design of N-halamine materials having fibrous structure, high halogen loading capacity with enhanced stability, and being relatively inexpensive is very important. This study investigated the effect of acid treatment on the chlorine loading and stability of a commercial flame retardant melamine formaldehyde (MF) fiber to introduce biocidal and detoxifying properties. The fibers formed into a web were treated with diluted sulfuric acid (H2SO4) under various conditions. The fiber webs were chlorinated with household bleach, and the stability of bound chlorine was investigated. The treated fabrics have been tested against a Gram-negative bacterium and a warfare stimulant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42799.

Fibers have been produced from a blend of poly(acrylonitrile) and poly(styrene hydantoin). The fibers were extruded from a single solvent, dimethyl acetamide. The fiber properties from the blended polymers were somewhat poorer than those from the unmodified acrylic fiber, but were still acceptable. The fibers from the polymer blend could be chlorinated to produce halamines and thus rendered antimicrobial. Antimicrobial test results showed efficacy against S. aureus. The ability to regenerate the halamines (and the antimicrobial functionality) lasted through 50 home laundry washings. The chlorine absorption was shown to be proportional to the specific surface area (m2/g) of the fibers, as might be expected for hydrophobic materials which can react with aqueous reagents only on the fiber surface. Although the fibers produced here were rather larger than those typically used in clothing, the data suggest that a typical diameter fiber of the composition produced here would have a specific surface area to allow chlorine absorption approaching 0.5 %. This level of retained chlorine would certainly produce a highly satisfactory antimicrobial effect - substantially better than the experimental data shown herein.

A new N-halamine precursor, 5-methyl-5-aminomethylhydantoin (AH), was synthesized. This N-halamine precursor can be coated onto cotton surfaces with the addition of the crosslinking agent butanetetracarboxylic acid (BTCA) and rendered biocidal by exposure to halogen solutions either before or after curing the coating or material. Standard washing tests show that covalently bound AH/BTCA on the cotton swatches can survive repeated washing cycles. After 50 washing cycles, chlorinated cotton swatches had lost 98.7 % of oxidative Cl+, but after rechlorination, almost 43.5 % of Cl+ was regained. Biocidal tests indicated that the cotton swatches coated with chlorinated AH/BTCA were effective against Gram positive Staphylococcus aureus and Gram negative Escherichia coli.

A novel, durable, long lasting, N -halamine siloxane monomer precursor, 5,5′-ethylenebis[5-methyl-3-(3-triethoxysilylpropyl)hydantoin] has been prepared and characterized by 1 H-NMR and FTIR for the purpose of functionalizing the surfaces of various materials. In this work, the precursor N -halamine moiety was attached by siloxane covalent bonding to surfaces of cotton fibers. Simulated laundering tests indicated that the chlorinated N -halamine structure could survive many repeated home launderings. The materials were rendered biocidal after exposure to oxidative halogen solutions, i.e. dilute household bleach. Once chlorinated, these materials were biocidal against Staphylococcus aureus and Escherichia coli . Upon loss of the halogen from either long-term use or consumption by the microbes on the surfaces, they could be simply recharged by further exposure to dilute bleach to regain biocidal activity.

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.

The monomer 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin and its hydrolysis product polymer poly[3-(5,5-dimethylhydantoinylpropyl)hydroxysiloxane] were employed to functionalize the surfaces of silica gel particles in order to produce an adhered film that becomes biocidal upon chlorination with dilute sodium hypochlorite bleach. The biocidal efficacy of the functionalized silica gel was demonstrated in a cartridge filter experiment against the bacterial pathogens Staphylococcus aureus and Escherichia coli O157:H7. Complete 6 log inactivations of the two bacterial species were observed within 30 s of contact. Moreover, upon loss of biocidal activity due to depletion of bound chlorine, the coated silica gel particles could be recharged by further exposure to dilute bleach. Potential uses of the biocidal silica gel include disinfection and odor control in water treatment facilities and recirculating baths. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3448–3454, 2006

Precursor 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.

Antimicrobial coatings on a wide variety of hard and soft substrates were prepared by exposing surfaces treated with novel N-halamine siloxane precursor monomers and macro-monomers to oxidative halogen solutions. Suspensions of a range of bacterial, viral, fungal and yeast micro-organisms were applied to the halogen-charged coatings for defined intervals, before recovery and quantification of surviving microbes using appropriate neutralisation and culture techniques. The biocidal surfaces exhibited powerful, broad-spectrum antimicrobial properties, inactivating most challenge microbes in contact times measured in minutes to hours, rather than the extended contact incubation periods usually associated with substrate-bound antimicrobial agents. Antimicrobial effects were also demonstrated to prevent odour caused by bacterial generation of ammonia in an experimental simulation of a urine-soaked nappy pad. Contact times for efficacy were related to bound halogen concentrations per unit of surface area. Potential benefits of these novel rechargeable biocidal surfaces cover a range, from limiting contamination of environmental surfaces with disease agents in healthcare or food service facilities, to controlling odour and mildew in bathrooms, and preventing odour formation in incontinence pads. They also confer antimicrobial protective functions on textiles and non-woven filter media for air and water.

The monomer 3-triethoxysilylpropyl-5,5-dimethylhydantoin has been polymerized on the surfaces of sand particles to produce an adhered film that, upon chlorination with dilute sodium hypochlorite bleach, becomes biocidal. The biocidal efficacy of this coated sand has been demonstrated in a cartridge filter experiment against the bacterial pathogens Staphylococcus aureus and Escherichia coli. Complete inactivation was observed within 1 min of contact for the former bacterium and in the interval of 1–5 min for the latter. Upon a loss of biocidal activity due to the depletion of bound chlorine, the coated sand particles can be recharged by further exposure to dilute bleach. Synthetic methods and test data are presented. Potential uses of biocidal sand include disinfection and odor control in water treatment facilities and recirculating baths. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1161–1166, 2005

Crosslinked chloromethylated polystyrene beads were reacted with hydantoin and imidazolidinone derivatives to produce functionalized beads which could be rendered biocidal upon reaction with free chlorine or bromine. The biocidal efficacies of the N-chlorinated, and in one case, the N-brominated polymeric beads against Staphylococcus aureus and Escherichia coli O157:H7 in aqueous suspension have been determined. Synthetic methods and test data have been presented. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 368–372, 2004

A comparison has been made between the biocidal efficacies of N-chlorinated polymeric beads and two derivatives of polyquat beads. Biocidal effects were measured after brief contact exposures of aqueous suspensions of either Staphylococcus aureus or Escherichia coli to the water-insoluble beads. The polymeric backbone was held the same in all three types of beads, so they differed only in their biocidal derivative moieties. In all cases, functionalization of crosslinked chloromethylated polystyrene beads was performed to introduce the biocidal properties. Synthetic methods and test data will be presented. The most effective biocide, as measured by degree of inactivation in the shortest contact time of the two species of bacteria, was the N-chlorinated hydantoinyl derivative of methylated polystyrene.