Self-Decontaminating Fibrous Materials Reactive toward Chemical Threats

Nonleaching Biocidal N-Halamine-Functionalized Polyamine-, Guanidine-, and Hydantoin-Based Coatings

Fibrous materials with inherent antimicrobial properties can help in real-time deactivation of microorganisms, enabling multiple uses while reducing secondary infections. Coatings with antiviral polymers enhance the surface functionality for existing and potential future pandemics. Herein, we demonstrated a straightforward route toward biocidal surface creation using polymers with nucleophilic biguanide, guanidine, and hydantoin groups that are covalently attached onto a solid support. Biocidal poly(N-vinylguanidine) (PVG) and poly(allylamine-co-4-aminopyridine-co-5-(4-hydroxybenzylidene)hydantoin) (PAH) were introduced for coating applications along with commercially available polyvinylamine (PVAm) and poly(hexamethylene biguanide) (PHMB). Nonleaching coatings were created by first fabricating bifunctional siloxane or isocyanate precursor coatings on the cotton, nylon-cotton, and glass fiber fabric, followed by the polymer attachment. The developed grafting methods ensured the stability of the coating and the reuse of the material while maintaining the biocidal properties. Halogenation of polymer-coated fabric was conducted by aqueous solutions of sodium hypochlorite or in situ generation of hypobromous acid (HOBr), resulting in surfaces coated by N-halamines with high contents of active > N-Cl or > N-Br groups. The polymer-coated fabrics were stable in multiple laundry cycles and maintained hydrophilic character after coating and halogenation. Halogenated polymer-coated fabrics completely inactivated human respiratory coronavirus based on a contact-killing mechanism and were shown to be reusable after recharging with bromine or chlorine.

Multifunctional polymeric guanidine and hydantoin halamines with broad biocidal activity

Prolonged and excessive use of biocides during the coronavirus disease era calls for incorporating new antiviral polymers that enhance the surface design and functionality for existing and potential future pandemics. Herein, we investigated previously unexplored polyamines with nucleophilic biguanide, guanidine, and hydantoin groups that all can be halogenated leading to high contents of oxidizing halogen that enables enhancement of the biocidal activity. Primary amino groups can be used to attach poly(N-vinylguanidine) (PVG) and poly(allylamine-co-4-aminopyridine-co-5-(4-hydroxybenzylidene)hydantoin) (PAH) as well as a broad-spectrum commercial biocide poly(hexamethylene biguanide) (PHMB) onto a solid support. Halogenation of polymer suspensions was conducted through in situ generation of excess hypobromous acid (HBrO) from bromine and sodium hydroxide or by sodium hypochlorite in aqueous solutions, resulting in N-halamines with high contents of active > N-Br or > N-Cl groups. The virucidal activity of the polymers against human respiratory coronavirus HCoV-229E increased dramatically with their halogenation. Brominated PHMB-Br showed activation activity value > 5 even at 1 mg/L, and complete virus inhibition was observed with either PHMB-Br or PAH-Br at 10 mg/mL. Brominated PVG-Br and PAH-Br possessed fungicidal activity against C. albicans, while PHMB was fungistatic. PHMB, PHMB-Br and PAH polymers demonstrated excellent bactericidal activity against the methicillin-resistant S. aureus and vancomycin-resistant E. faecium. Brominated polymers (PHMB-Br, PVG-Br, PAH-Br) were not toxic to the HeLa monolayers, indicating acceptable biocompatibility to cultured human cells. With these features, the N-halamine polymers of the present study are a worthwhile addition to the arsenal of biocides and are promising candidates for development of non-leaching coatings.

Functionalized reactive polymers for the removal of chemical warfare agents: A review

Protection from and removal of chemical warfare agents (CWAs) from the environment remains a global goal. Activated charcoal, metal oxides, metal organic frameworks (MOFs), polyoxometalates (POMs) and reactive polymers have all been investigated for CWA removal. Composite polymeric materials are rapidly gaining traction as versatile building blocks for personal protective equipment (PPE) and catalytic devices. Polymers are inexpensive to produce and easily engineered into a wide range of materials including films, electro-spun fibers, mixed-matrix membranes/reactors, and other forms. When containing reactive side-chains, hydrolysis catalysts, and/or oxidative catalysts polymeric devices are primed for CWA decontamination. In this review, recent advances in reactive polymeric materials for CWA removal are summarized. To aid in comparing the effectiveness of the different solid catalysts, particular attention is paid to the stoichiometric ratio of reactive species to toxic substrate (CWA or CWA simulant).

Daylight-activated fumigant detoxifying nanofibrous membrane based on thiol-ene click chemistry

Daylight-activated detoxifying nanofibrous membranes (LDNMs) are fabricated by grafting benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BD) and biological thiols successively on poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous membrane. Taking the merits of photoactivity of BD, high-reactivity of biological thiols, and high specific surface area and porosity of the nanofibrous membrane, 1,3-dichloropropene (1,3-D) can be efficiently detoxified on the LDNMs under daylight irradiation via a thiol-ene click reaction. The detoxification function of the LDNMs is "switched on" by light irradiation and continues by following a cascade of chemical attacks of thiyl radicals formed during the photoexcitation process. The resultant LDNMs present rapid detoxification rate (i.e., t1/2 =~30 min) and massive detoxification amount (i.e., ~12 mg/g) against 1,3-D vapor under ambient conditions. More importantly, the LDNMs perform a detoxification tailing effect after moving the light-irradiated membrane to a dark environment, thus ensuring the protective function in the absence of sufficient light sources. The detoxification property of the LDNMs in an outdoor environment with sunlight irradiation shows comparable results to the lab-scale outcomes, enabling them to serve as innovative materials for personal protective equipment in practical applications. The successful fabrication of LDNMs may inspire new insights into the design of protective materials providing aggressive protection.

Dual-purpose high-efficiency air filter paper loaded with reactive zirconium hydroxide for the filtration aerosols and degradation of chemical warfare agents

Traditional air filter papers can only filter toxic aerosols without the function of decontamination. If the poison stagnating in the paper is desorbed, it may pose a secondary threat to personnel and make it more difficult to dispose of the scrapped paper. Using an alkali-free glass fiber as the base material and zirconium hydroxide as the decontaminant, a self-decontaminating air filter paper that can degrade HD and VX simultaneously was successfully prepared by an intra-pulp addition method, with high filtration efficiency, low pressure drop and moderate tensile strength. The physicochemical properties were characterized by FE-SEM, EDX, XRD and TGA, and the results indicated that Zr(OH)₄ was dispersed uniformly in the paper and filled in the interstices of the glass fiber. The preparation of the composite material had no impact on the structure of fibers and Zr(OH)₄. The preparation technology of the self-decontaminating air filter paper was optimized. It was found that the paper with a fiber grammage of 50 g m⁻², the adhesive of 2% and a Zr(OH)₄ retention rate of 175.0 wt% could completely degrade HD and VX, whose conversion rate exceeded 99.0%, and had a tensile strength of 0.1193 kN m⁻¹, a filtration efficiency of 99.995%, and a pressure drop of 313.6 Pa. Using GC-MS to detect the decontamination products, it was speculated that HD mainly underwent hydrolysis and elimination reactions, VX mainly underwent hydrolysis and polymerization reactions, and their products were non-toxic or low-toxic. The reaction kinetics of HD and VX on the paper was investigated and the half-lives were 2.6 h and 16.2 min, respectively, which demonstrated an outstanding degradation performance. This work manifested for the first time that the air filter paper can be optimized as an efficient self-decontaminating material, which will open up new possibilities for the design and manufacture of multifunctional protective materials.

Dual-functional air filter paper with addition of Zr(OH)₄ was prepared by an intra-pulp addition method, whose filtration performance is maintained while the decontamination performance is added for HD and VX.

Air Activated Self-Decontaminating Polydicyclopentadiene PolyHIPE Foams for Rapid Decontamination of Chemical Warfare Agents

The threat of chemical warfare agents (CWA) compels research into novel self-decontaminating materials (SDM) for the continued safety of first-responders, civilians, and active service personnel. The capacity to actively detoxify, as opposed to merely sequester, offending agents under typical environmental conditions defines the added value of SDMs in comparison to traditional adsorptive materials. Porous polymers, synthesized via the high internal phase emulsion (HIPE) templating, provide a facile fabrication method for materials with permeable open cellular structures that may serve in air filtration applications. PolyHIPEs comprising polydicyclopentadiene (polyDCPD) networks form stable hydroperoxide species following activation in air under ambient conditions. The hydroperoxide-containing polyDCPD materials react quickly with CWA simulants, Demeton-S and 2-chloroethyl ethyl sulfide, forming oxidation products as confirmed via gas chromatography mass spectrometry. The simplicity of the detoxification chemistry paired with the porous foam form factor presents an exciting opportunity for the development of self-decontaminating filter media.

Mustard Gas Surrogate Interactions with Modified Porous Carbon Fabrics: Effect of Oxidative Treatment

Removal of chemical warfare agent (CWA) surrogates by highly porous carbon textiles was investigated. The carbon cloth was modified by oxidation in a mixture of concentrated sulfuric and nitric acid. This process did not affect textile structural integrity. The surface properties of the modified textiles were investigated, and their capabilities to remove 2-chloroethyl ethyl sulfide (CEES) and diethylsulfide (EES), two mustard gas surrogates, were evaluated. The oxidized carbon textiles have a highly active surface that has the ability to form radical species. This enhances the degradation of the surrogates, and so the detoxification efficiency. The reaction products detected suggest differences in degradation mechanisms which depend on the type of fabric surface features. Thus, the oxidized surfaces eliminate CEES mainly through dehydrohalogenation, while the nonoxidized surfaces act via hydrolysis. Only the oxidized carbon has a surface active enough to react with the less reactive surrogate EES, by cleavage of the C-S bond. The surface functional groups promote not only the radical formation but also contribute to a strong adsorption of the CWA surrogates, which enhance the decomposition of these toxic species.

Carbon Textiles Modified with Copper-Based Reactive Adsorbents as Efficient Media for Detoxification of Chemical Warfare Agents

Carbon textile swatch was oxidized and impregnated with copper hydroxynitrate. A subsample was then further heated at 280 °C to form copper oxide. The swatches preserved their integrity through the treatments. As final products, they exhibited remarkable detoxification properties for the nerve agent surrogate dimethyl chlorophosphate (DMCP). Based on the amount of reactive copper phases deposited on the fibers, their adsorption capacities were higher than those of the bulk powders. After 1 day exposure to DMCP (1:1 weight ratio adsorbent/DMCP), 99% of the initial amount of DMCP was eliminated. A synergistic effect of the composite components was clearly seen. GC-MS results showed that the main surface reaction product was chloromethane. Its formation indicated hydrolysis as a detoxification path. Surface analyses showed phosphate bonding to the fibers and formation of copper chloride. The appearance of the latter species results in a clear textile color change, which suggests the application of these fabrics not only as catalytic protection agents but also as sensors of nerve agents.

MOFabric: Electrospun Nanofiber Mats from PVDF/UiO-66-NH2 for Chemical Protection and Decontamination

Textiles capable of capture and detoxification of toxic chemicals, such as chemical-warfare agents (CWAs), are of high interest. Some metal-organic frameworks (MOFs) exhibit superior reactivity toward CWAs. However, it remains a challenge to integrate powder MOFs into engineered materials like textiles, while retaining functionalities like crystallinity, adsorptivity, and reactivity. Here, we present a simple method of electrospinning UiO-66-NH₂, a zirconium MOF, with polyvinylidene fluoride (PVDF). The electrospun composite, which we refer to as "MOFabric", exhibits comparable crystal patterns, surface area, chlorine uptake, and simulant hydrolysis to powder UiO-66-NH₂. The MOFabric is also capable of breaking down GD (O-pinacolyl methylphosphonofluoridae) faster than powder UiO-66-NH_2. Half-life of GD monitored by solid-state NMR for MOFabric is 131 min versus 315 min on powder UiO-66-NH₂.