An open-pore MFI zeolite nanosheet-modified separator with Li-ion flux regulation for lithium-metal batteries.

Separator modification has become one of the most facile and promising methods to inhibit Li dendrite formation. Herein, an open-pore MFI zeolite nanosheet-modified polyacrylonitrile (open-pore MFI NSs@PAN) separator was prepared via the combination of vacuum filtration and the electrospinning technique. The straight channels in the MFI NSs, the fluid channels formed by the stacking of the MFI NSs and the interconnected network channels formed by the interweaving of the PAN nanofibers jointly constructed a micro/nano pore structure, which provides sufficient Li+ transport channels and enables uniform Li+ flux. Consequently, the open-pore MFI NSs@PAN separator-based cell delivers a stable and uniform Li deposition, demonstrating a more stable cycle-life and better rate capability. Redistributing Li+ flux through straight channel zeolite nanosheets provides a powerful method for suppressing Li dendrites, presenting enormous potential for promoting the commercial application of lithium metal batteries.

Polyacrylonitrile/UV329/titanium oxide composite nanofibrous membranes with enhanced UV protection and filtration performance.

Ultraviolet (UV) radiation is extremely dangerous to humans and can contribute to immunosuppression, erythema, early ageing and skin cancer. UV protection finishing may greatly influence the handling and permeability of fabrics, while UV-proof fibres can guarantee close contact between UV-resistant agents and fabric without affecting the handling of the fabric. In this study, polyacrylonitrile (PAN)/UV absorber 329 (UV329)/titanium dioxide (TiO2) composite nanofibrous membranes with complex, highly efficient UV resistance were fabricated via electrospinning. UV329 was included in the composite to further strengthen the UV resistance properties via absorption function, while TiO2 inorganic nanoparticles were added to provide UV shielding function. The presence of UV329 and TiO2 in the membranes was confirmed using Fourier-transform infrared spectroscopy, which also showed the absence of chemical bonds between PAN and the anti-UV agents. The PAN/UV329/TiO2 membranes exhibited a UV protection factor of 1352 and a UVA transmittance of 0.6%, which indicate their extraordinary UV resistance properties. Additionally, filtration performance was investigated in order to expand the application field of the UV-resistant PAN/UV329/TiO2 membranes, and the composite nanofibrous membranes showed a UV filtration efficiency of 99.57% and a pressure drop of 145 Pa. The proposed multi-functional nanofibrous membranes have broad application prospects in outdoor protective clothing and window air filters.

Fluorine-Free Hydrophobic Modification and Waterproof Breathable Properties of Electrospun Polyacrylonitrile Nanofibrous Membranes.

Waterproof breathable functional membranes have broad application prospects in the field of outdoors textiles. The fluorine-containing microporous membranes of the mainstream functional products easily cause harm to the environment, and thus, the fluorine-free environmental nanofibrous membranes are an important development direction for functional membranes. In this subject, the electrospun polyacrylonitrile nanofibrous membranes were first hydrophobically modified by amino functional modified polysiloxane (AMP), followed by in situ cross-linking modified with 4, 4'-methyl diphenylene diisocyanate (MDI). The fluorine-free modification by AMP altered the surface of the membranes from hydrophilic to hydrophobic, and greatly improved the waterproof properties with the hydrostatic pressure reaching to 87.6 kPa. In addition, the formation of bonding points and the in situ preparation of polyuria through the reaction between the isocyanate in MDI and the amino group in AMP, could improve the mechanical properties effectively. When using AMP with the concentration of 1 wt% and MDI with the concentration of 2 wt%, the relatively good comprehensive performance was obtained with good water resistance (93.8 kPa), modest vapor permeability (4.7 kg m-2 d-1) and air permeability (12.7 mm/s). Based on these testing data, the modified nanofibrous membranes had excellent waterproof and breathable properties, which has future potential in outdoor sports apparel.

In situ deposition of nano Cu2O on electrospun chitosan nanofibrous scaffolds and their antimicrobial properties.

In order to obtain a synergistic antimicrobial effect of cuprous oxide nanoparticles (Cu2O NPs) and chitosan (CS) nanofibers, the nano Cu2O/CS nanofibrous scaffolds were synthesized in situ via two subsequent steps of chelation and reduction. The Cu2+ were stably chelated on CS nanofibrous scaffolds through the coordination of amino group (-NH2) and hydroxyl group (-OH) on CS with Cu2+, and then the chelated Cu2+ were reduced to nano Cu2O by Vitamin C under alkaline conditions. And by the measurements of XRD, XPS and FTIR-ATR, the results showed that Cu2O NPs were successfully deposited on the CS nanofibrous scaffolds. SEM clarified that the particle size of Cu2O gradually decreased and the shape changed from cubic to irregular with the increase of CuSO4 concentration. With the CuSO4 concentration of 0.02 and 0.04 mol·L-1, the Cu2O/CS nanofibrous scaffolds presented outstanding hydrophilicity and antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) comparing to the CS nanofibrous scaffolds, meanwhile, they possessed good biocompatibility. This kind of nanofibrous scaffolds deposited with nano Cu2O would have broad application prospects in the field of antibacterial biomaterials.

Completely amorphous cellulose biosynthesized in agitated culture at low temperature.

The morphology and structure of the biosynthesized cellulose are related to the culture methods and conditions. In order to investigate the detail culture conditions, the Gluconacetbacter xylinum 1.1812 (ATCC 23767) strains were cultivated in static culture at 12 and 30 °C, and agitated culture at 12 °C. The cellulose samples were analyzed by FESEM, FTIR, CP/MAS 13C NMR, WAXRD and TGA. The cellulose membrane produced in static medium at 30 °C is made up of the microfibrils with a width of 60-90 nm, which has highest crystallinity index and the most content of cellulose Iα. The cellulose membrane produced in static medium at 12 °C is accumulated by the pellicles with a thickness of ~10 nm and a width of 700-3000 nm, which is cellulose I crystalline structure. The macroscopic sphere-like cellulose produced in agitated culture at 12 °C is composed of flat, strongly twisted cellulose bands with a width of 700-1200 nm, and reveals completely amorphous structure which exhibits only the diffuse X-ray diffraction pattern, lack of characteristic crystalline peaks. This work provides a new method to prepare amorphous cellulose.

Functional modification of breathable polyacrylonitrile/polyurethane/TiO2 nanofibrous membranes with robust ultraviolet resistant and waterproof performance.

Exploiting high-added-value textiles equipped with multiple functionalities like ultraviolet (UV) resistance, waterproofness, and thermal-moisture comfort is facing tremendous demand by a more discerning consumer market. However, the major challenge is to realize the equilibrium among the multifunction. Herein, a new attempt of fabricating superhydrophobic electrospun polyacrylonitrile (PAN)/polyurethane (PU)/titanium dioxide (TiO2) nanofibrous membranes has been tried, and the membranes exhibited multifunction of UV resistance, waterproofness and breathability by coating modification with 2-hydroxy-4-n-octoxybenzophenone (UV531) and fluorinated acrylic copolymer (FAC). TiO2 NPs as inorganic blocker and UV531 as organic absorber were utilized to impart the excellent double UV resistant function for the modified nanofibrous membranes. The hydrophobic coating with FAC endowed the pristine membranes with enhanced superhydrophobic wettability and the advancing contact angle was 152.1°. Regulating the addition amount of TiO2 NPs, the UV531 and FAC concentration, the multiple functionalities of the modified PAN/PU/TiO2 were systemically optimized: robust tensile strength (14.6MPa), good ultraviolet protection factor of 1485, modest waterproofness (62kPa), and moisture breathability (12.9kgm-2 d-1). The equilibrium among the multifunction of the as-prepared membranes indicated their diverse possibilities can be used in various applications, including high-altitude garments, protective clothing, covering materials, self-cleaning materials, and other medical products.

Environmentally Friendly and Breathable Fluorinated Polyurethane Fibrous Membranes Exhibiting Robust Waterproof Performance.

Waterproof and breathable membranes that provide a high level of protection and comfort are promising core materials for meeting the pressing demand for future upscale protective clothing. However, creating such materials that exhibit environmental protection, high performance, and ease of fabrication has proven to be a great challenge. Herein, we report a novel strategy for synthesizing fluorinated polyurethane (C6FPU) containing short perfluorohexyl (-C6F13) chains and introduced it as hydrophobic agent into a polyurethane (PU) solution for one-step electrospinning. A plausible mechanism about the dynamic behavior of fluorinated chains with an increasing C6FPU concentration was proposed. Benefiting from the utilization of magnesium chloride (MgCl2), the fibrous membranes had dramatically decreased maximum pore sizes. Consequently, the prepared PU/C6FPU/MgCl2 fibrous membranes exhibited an excellent hydrostatic pressure of 104 kPa, a modest water vapor transmission rate of 11.5 kg m-2 d-1, and a desirable tensile strength of 12.4 MPa. The facile fabrication of PU/C6FPU/MgCl2 waterproof and breathable membranes not only matches well with the tendency to be environmentally protective but also fully meets the requirements for high performance in extremely harsh environments.

Robust Fluorine-Free Superhydrophobic Amino-Silicone Oil/SiO2 Modification of Electrospun Polyacrylonitrile Membranes for Waterproof-Breathable Application.

Superhydrophobic waterproof-breathable membranes have attracted considerable interest owing to their multifunctional applications in self-cleaning, anti-icing, anticorrosion, outdoor tents, and protective clothing. Despite the researches pertaning to the construction of superhydrophobic functional membranes by nanoparticle finishing have increased drastically, the disconnected particle component is easy to fall off from the membranes under deformation and wear conditions, which has restricted their wide use in practice. Here, robust superhydrophobic microporous membranes were prepared via a facile and environmentally friendly strategy by dip-coating amino-silicone oil (ASO) onto the electrospun polyacrylonitrile (PAN) membranes, followed by SiO2 nanoparticles (SiO2 NPs) blade coating. Compared with hydrophilic PAN membranes, the modified membranes exhibited superhydrophobic surface with an advancing water contact angle up to 156°, after introducing ASO as low surface energy substance and SiO2 NPs as filler to reduce the pore size and construct the multihierarchical rough structure. Varying the concentrations of ASO and SiO2 NPs systematically, the PAN electrospun membranes modified with 1 wt % ASO and 0.1 wt % SiO2 NPs were endowed with good water-resistance (74.3 kPa), relative low thermal conductivity (0.0028 W m-1 K-1), modest vapor permeability (11.4 kg m-2 d-1), and air permeability (20.5 mm s-1). Besides, the inorganic-organic hybrid coating of ASO/SiO2 NPs could maintain its superhydrophobicity even after 40 abrasion cycles. The resulting membranes were found to resist variations on the pH scale from 0 to 12, and retained their water repellent properties when exposed to harsh acidic and alkali conditions. This facile fabrication of durable fluorine-free superhydrophobic membranes simultaneous with good waterproof-breathable performance provides the advantages for potential applications in self-cleaning materials and versatile protective clothing.

Tailoring Water-Resistant and Breathable Performance of Polyacrylonitrile Nanofibrous Membranes Modified by Polydimethylsiloxane.

The demand of water-resistant and breathable materials applied to a separation medium and protective garments is steadily increasing. Typical approaches to obtain these functional materials are based on hydrophobic agents and porous substrates with small fiber diameter, tiny pore, and high porosity. However, a fluorinated hydrophobic finishing agent usually employed in providing effective waterproofness is limited with respect to their environmental persistence and toxic potential. Herein, with the aim to keep a balance between the water-resistance and breathability as well as mechanical properties, we fabricate a novel fluoride-free functional membrane by electrospun polyacrylonitrile (PAN) nanofibers modified with polydimethylsiloxane (PDMS). As determined by morphological, DSC, and FT-IR analyses, the curing reaction of PDMS macromolecules formed an abundance of hydrophobic adhesive structures, which improved the waterproof performance dramatically and imparted relative good breathability at the same time. By systematically tuning the curing temperature as well as the concentration of PDMS, the modified PAN membranes with 4 wt % PDMS possessed good water-resistance (80.9 kPa), modest vapor permeability (12.5 kg m-2 d-1), and air permeability (9.9 mm s-1). Compared with pristine PAN membranes, the modified membranes were endowed with enhanced tensile stress of 15.7 MPa. The good comprehensive performance of the as-prepared membranes suggested their potential applications in protective clothing, membrane distillation, self-cleaning materials, and other medical products. Furthermore, the proposed relationship between porous structure and waterproof/breathable property as one considerable principle is applicable to designing functional membranes with different levels of protective and comfortable performance.

Superamphiphobic nanofibrous membranes for effective filtration of fine particles.

The worldwide demands are rising for an energy-efficient and cost-effective approach that can provide advanced nanofibrous membranes with high filtration performance and superior antifouling properties. Here we report a novel synthesized fluorinated polyurethane (FPU) modified nanofibrous membrane optimized to achieve oil and non-oil aerosol particle filtration. By employing the FPU incorporation, the polyacrylonitrile/polyurethane (PAN/PU) composite membranes were endowed with superhydrophobicity with a water contact angle of 154° and superoleophobicity with an oil contact angle of 151°. Morphology, surface wettability, porous structure, and filtration performance could be manipulated by tuning the solution composition as well as the hierarchical structure. Furthermore, the as-prepared membranes can capture, for the first time, a range of different oil aerosol particles in a single-unit operation, with >99.9% filtration efficiency, by using the combined contribution of fiber diameter and surface roughness acting on the objective particles. Exemplified here by the construction of superamphiphobic nanofibrous membrane, numerous applications of this medium includes high efficiency particulate air filters, ultra-low penetration air filters, and respiratory protection equipment.