Superelastic, Breathable, and High-Barrier Nanofibrous Membranes with Biomimetic ECM Structure for Toxic Chemical Protection

UV-Cured Highly Crosslinked Polyurethane Acrylate to Serve as a Barrier against Chemical Warfare Agent Simulants

Ultraviolet (UV) curing is an efficient and environmentally friendly curing method. In this paper, UV-cured polyurethane acrylates (PUAs) were investigated as potential military coatings to serve as barriers against chemical warfare agents (CWAs). Seven UV-cured PUA coatings were formulated utilizing hydroxyethyl methacrylate-capped hexamethylene diisocyanate trimer (HEMA-Htri) and trimethylolpropane triacrylate-capped polycarbonate prepolymer (PETA-PCDL) as the PUA monomers. Isobornyl acrylate (IBOA) and triethyleneglycol divinyl ether (DVE-3) were employed as reactive diluents. Gas chromatography was utilized to investigate the constitutive relationships between the structures of the PUA coatings and their protective properties against simulant agents for CWAs, including dimethyl methylphosphonate (DMMP), a nerve agent simulant, and 2-chloroethyl ethyl sulfide (CEES), a mustard simulant. The glass transition temperature (Tg) and crosslinking density (υe) of PUAs were found to be crucial factors affecting their ability to serve as barriers against CWAs. The incorporation of IBOA units led to enhanced Tg and barrier performance of the PUAs, resulting in a DMMP retention of less than 0.5% and nearly 0 retention of CEES. However, an excessive introduction of polycarbonate chains decreased the υe and barrier performance of the PUAs. These findings may offer valuable insights for enhancing the protection of UV-cured PU coatings against CWAs.

Dehydrated Biomimetic Membranes with Skinlike Structure and Function

Novel vapor-permeable materials are sought after for applications in protective wear, energy generation, and water treatment. Current impermeable protective materials effectively block harmful agents but trap heat due to poor water vapor transfer. Here we present a new class of materials, vapor permeable dehydrated nanoporous biomimetic membranes (DBMs), based on channel proteins. This application for biomimetic membranes is unexpected as channel proteins and biomimetic membranes were assumed to be unstable under dry conditions. DBMs mimic human skin's structure to offer both high vapor transport and small molecule exclusion under dry conditions. DBMs feature highly organized pores resembling sweat pores in human skin, but at super high densities (>1012 pores/cm2). These DBMs achieved exceptional water vapor transport rates, surpassing commercial breathable fabrics by up to 6.2 times, despite containing >2 orders of magnitude smaller pores (1 nm vs >700 nm). These DBMs effectively excluded model biological agents and harmful chemicals both in liquid and vapor phases, again in contrast with the commercial breathable fabrics. Remarkably, while hydrated biomimetic membranes were highly permeable to liquid water, they exhibited higher water resistances after dehydration at values >38 times that of commercial breathable fabrics. Molecular dynamics simulations support our hypothesis that dehydration induced protein hydrophobicity increases which enhanced DBM performance. DBMs hold promise for various applications, including membrane distillation, dehumidification, and protective barriers for atmospheric water harvesting materials.

Ultralight and Superelastic Gd2O3/Bi2O3 Nanofibrous Aerogels with Nacre-Mimetic Brick-Mortar Structure for Superior X-ray Shielding

The widespread use of X-rays has prompted a surge in demand for effective and wearable shielding materials. However, the Pb-containing materials currently used to shield X-rays are commonly bulky, hard, and biotoxic, severely limiting their applications in wearable scenarios. Inspired by the nacre, we report on ultralight, superelastic, and nontoxic X-ray shielding nanofibrous aerogels with microarch-engineered brick/mortar structure by combining polyurethane/Bi₂O₃ nanofibers (brick) and Gd₂O₃ nanosheets (mortar). The synergistic attenuation effect toward X-rays from the reflection of microarches and absorption of Bi/Gd elements significantly enhances the shielding efficiency of aerogels, and microarches/robust nanofibrous networks endow the materials with superelasticity. The resultant materials exhibit integrated properties of superior X-ray shielding efficiency (91-100%), ultralow density (52 mg cm^-3), large stretchability of 800% reversible elongation, and high water vapor permeability (8.8 kg m^-2 day^-1). The fabrication of such novel aerogels paves the way for developing next-generation effective and wearable X-ray shielding materials.

Waterproof, breathable and infrared-invisible polyurethane/silica nanofiber membranes for wearable textiles

Waterproof and breathable membranes, which have great potential in applications such as membrane distillation, self-cleaning, and multifunctional clothing, have attracted a lot of attention due to their superior performance. Superhydrophobic and infrared-invisible polyurethane (PU)/silica (SiO₂) nanofiber microporous membranes were prepared by facile electrospinning and a hydrothermal-assisted sol-gel method. Compared with pure PU nanofiber membranes, silica nanoparticles act as an adhesion layer, which can provide the rough surface and low surface energy of fibrous membranes. Therefore, the grafted PU/SiO₂ nanofiber membrane was endowed with a good superhydrophobic effect, and its water contact angle (WCA) reached 161°. The nanofiber membrane exhibited comfortable waterproof and breathable properties, in which the air permeability and water vapor transfer rate was 5.18 mm s^-1 and 7.85 kg m^-2 d^-1, respectively. When the PU/SiO₂ nanofiber membrane was irradiated by infrared light, the surface of the fiber membrane showed a green, low-temperature state. These waterproof and breathable nanofiber membranes with superhydrophobic properties could be used in anti-icing, outdoor concealment, and camouflage applications.