Rational Design of Oil-Resistant and Electrically Conductive Fluorosilicone Rubber Foam Nanocomposites for Sensitive Detectability in Complex Solvent Environments.

Recent years have witnessed the explosive development of highly sensitive smart sensors based on conductive polymer foam materials. However, the design and development of multifunctional polymeric foam composites as smart sensors applied in complex solvent and oil environments remain a critical challenge. Herein, we design and synthesize vinyl-terminated polytrifluoropropylmethylsiloxane through anionic ring-opening polymerization to fabricate fluorosilicone rubber foam (FSiRF) materials with nanoscale wrinkled surfaces and reactive Si-H groups via a green and rapid chemical foaming strategy. Based on the strong adhesion between FSiRF materials and consecutive oxidized ketjen black (OKB) nano-network, multifunctional FSiRF nanocomposites were prepared by a dip-coating strategy followed by fluoroalkylsilane modification. The optimized F-OKB@FSiRF nanocomposites exhibit outstanding mechanical flexibility in wide-temperature range (100 cycle compressions from -20 to 200 °C), structure stability (no detached particles after being immersed into various aqueous solutions for up to 15 days), surface superhydrophobicity (water contact angle of 154° and sliding angle of ∼7°), and tunable electrical conductivity (from 10-5 to 10-2 S m-1). Additionally, benefiting from the combined actions of multiple lines of defense (low surface energy groups, physical barriers, and "shielding effect"), the F-OKB@FSiRF sensor presents excellent anti-swelling property and high sensitivity in monitoring both large-deformation and tiny vibrations generated by knocking the beaker, ultrasonic action, agitating, and sinking objects in weak-polar or nonpolar solvents. This work conceivably provides a chemical strategy for the fabrication of multifunctional polymeric foam nanocomposite materials as smart sensors for broad applications.

Green fabrication of durable foam composites with asymmetric wettability by an emulsion spray-coating method for photothermally induced crude oil cleanup.

Chemical spills, especially oil spills, are becoming an increasingly serious environmental issue. It remains a challenge to develop green techniques to prepare mechanically robust oil-water separation materials, especially those capable of separating high-viscosity crude oils. Herein, we propose an environmentally friendly emulsion spray-coating method to fabricate durable foam composites with asymmetric wettability for oil-water separation. After the emulsion, composed of acidified carbon nanotubes (ACNTs), polydimethylsiloxane (PDMS) and its curing agent, is sprayed onto melamine foam (MF), water in the emulsion is first evaporated, while PDMS and ACNTs are finally deposited on the foam skeleton. The foam composite exhibits gradient wettability and turns from superhydrophobicity of the top surface (the water contact angle reaches as high as 155.2°) to hydrophilicity of the interior region. The foam composite can be used for the separation of oils with different densities and has a 97% separation efficiency for chloroform. In particular, the photothermal conversion-induced temperature rise can reduce the oil viscosity and complete the high-efficiency cleanup of crude oil. This emulsion spray-coating technique and asymmetric wettability show promise for the green and low-cost fabrication of high-performance oil/water separation materials.

Chitosan assisted MXene decoration onto polymer fabric for high efficiency solar driven interfacial evaporation of oil contaminated seawater.

The solar-driven interfacial evaporation (SDIE) is now a promising way to solve the shortage of fresh water. However, high performance SDIE for the oil contaminated seawater remains challenging. Here, we propose a facile "chitosan assisted MXene decoration" strategy to prepare a superhydrophilic and underwater superoleophobic Chitosan/MXene/fabric (CMF) for highly efficient SDIE. Benefiting from the superhydrophilicity and excellent photo-thermal conversion performance, the CMF is served as both the solar absorber and the water transportation path. Under the light illumination with one sun intensity (1 kW·m-2), a high evaporation rate of 1.50 kg·m-2·h-1 and efficiency of 88.05% are achieved. The strong interfacial interaction and outstanding salt rejection behavior of the CMF ensure the SDIE long-term stability and durability. In addition, the underwater superoleophobic CMF can effectively and quickly repel different oils and is hence suitable for high performance SDIE of the oil-in-water emulsion and the crude oil contaminated seawater. This work provides a rational design and optimization for the SDIE system, which holds great potential in practical desalination applications.

Superhydrophobic, electrically conductive and multifunctional polymer foam composite for chemical vapor detection and crude oil cleanup.

The leakage of chemicals (either vapors or liquids) severely threatens the environment and even people's health. It remains a great challenge to develop multifunctional and durable materials that can not only detect the chemical vapors but also clean up the liquid chemicals especially high viscous crude oil. Here, a superhydrophobic and conductive foam composite (SCFC) is prepared by decorating carbon black nanoparticles (CBNPs) onto the skeleton of the pre-swollen polymer foam under the assistance of ultrasonication. The CBNPs are firmly embedded onto the skeleton surface, exhibiting a strong interfacial adhesion and hence excellent surface stability and durability. The SCFC possesses stable vapor sensing behavior and can detect various chemical vapors with a low detection limit and good cycling performance. When used for oil/water separation, the SCFC has large oil adsorption capacity for different oils with excellent reusability. Also, the outstanding photo-thermal conversion performance of the SCFC can be used to significantly reduce the oil viscosity and hence realize efficient cleanup of the crude oil. The multifunctional SCFC has promising applications in the field of environment protection, flexible electronics, etc.

Skin-inspired thermoelectric nanocoating for temperature sensing and fire safety.

Temperature sensing enables flammable materials to respond intelligently at high temperature, which is conducive to further improving their fire safety. However, it is still challenging to develop a smart nanocoating with sensitive temperature-sensing and efficient flame retardancy. Inspired by human skin, a thermoelectric flame retardant (TE-FR) nanocoating was fabricated by combining a dermis-mimicking thermoelectric (TE) layer and an epidermis-mimicking flame retardant (FR) layer. The TE-FR nanocoating exhibited accurate temperature sensing at 100-300 ℃ and repeatable fire-warning capability. When being burned, the fire-warning response time of the TE-FR nanocoating was only 2.0 s, and it retriggered the fire-warning device within 2.8 s when it was reburned. Meanwhile, the TE-FR nanocoating exhibited outstanding flame retardancy. The coated polypropylene self-extinguished in the horizontal and vertical burning tests. Besides, its peak heat release rate, total heat release, and peak smoke production rate were significantly reduced. This work proposed an ingenious strategy to fabricate smart nanocoating for temperature sensing and fire safety, which revealed an enticing prospect in the fields of fire protection, electronic skin, and temperature monitor.

A sandwich structured drug delivery composite membrane for improved recovery after spinal cord injury under longtime controlled release.

A sandwich structured composite membrane for longtime controlled release of nerve growth factor (NGF) to repair spinal cord injury (SCI) is prepared through electrospray. In this system, PLA film is used as the sealing layer to prevent drug diffusion and provide mechanical support, PLGA microspheres as the sandwich layer to load and controlled release NGF, and chitosan (CS) film as the planting layer to seed bone marrow mesenchymal stem cells (BMSCs). The composite membrane has good biocompatibility and can effectively promote PC-12 cells to differentiate into neurons. In addition, the composite membrane can be directly applied to the injured areas without further damage. The longtime sustained release of NGF guaranteed enough requirement time for SCI repair, which will decrease the administration frequency and improve patient compliance. The administration of BMSCs coupled with the sandwich composite membrane effectively relieves SCI, decreases cavity formation, enhances neuronal regeneration and tissue repair, as well as improves the recovery of locomotor functions. Overall, this present work provides a future perspective for the treatment of SCI by the NGF-loaded sandwich composite membrane with prolonged drug release function.

Carbon nanofiber based superhydrophobic foam composite for high performance oil/water separation.

Oil spill has now been a serious environmental issue, threatening the aquatic ecosystems and even human living environment. It is still challenging to develop absorbents for efficient oil/water emulsion separation and clean-up of viscous crude oil. Here, we propose a facile method to fabricate flexible and superhydrophobic foam composites for high efficiency oil/water separation under different complex environment. Carbon nanofibers (CNFs) with a hollow structure are decorated uniformly onto the skeleton of the polydimethylsiloxane (PDMS) foam with a strong interfacial adhesion. CNFs could not only enhance the surface roughness and thus the hydrophobicity but also be served as numerous capillary tubes, improving the oil adsorption and oil/water separation performance. More importantly, the CNFs network with a strong light absorption endows the foam with superior photo-thermal conversion capability. The obtained foam composite possesses excellent corrosion resistance and can adsorb various kinds of oil with different densities. The foam composite is able to separate the oil from the emulsion with a relatively high separation efficiency. The material surface temperature is able to quickly increase under the light irradiation, which can significantly reduce the oil viscosity and hence achieve the rapid clean-up of the crude oil floating on water surface.

Flexible and Superhydrophobic Composites with Dual Polymer Nanofiber and Carbon Nanofiber Network for High-Performance Chemical Vapor Sensing and Oil/Water Separation.

Polymer nanofiber composites with superhydrophobicity are promising for the chemical vapor sensing or oil/water separation, but it remains challenging to develop superhydrophobic, anticorrosive, and durable nanofiber composites that can achieve both the organic solvent vapor detection and oil (organic solvent)/water separation with high separation flux and excellent recyclability. Here, a flexible, stretchable, and superhydrophobic/superoleophilic nanofiber composite membrane with excellent photothermal conversion performance is fabricated by decorating carbon nanofibers (CNFs) with a hollow structure onto the polyurethane nanofibers and subsequent polydimethylsiloxane (PDMS) modification. The combination of CNFs and PDMS greatly improves the membrane's tensile strength and Young's modulus without sacrificing its stretchability. The dual polymer nanofiber and CNF network are beneficial to the chemical vapor or liquid diffusion into the membrane and thus can be used for high-performance chemical vapor sensing and oil/water separation. The nanofiber composite is responsive to different organic vapors with a low detection limit and good selectivity. Also, the material can achieve fast oil/water separation with the oil (dichloromethane) permeate flux as high as 6577.3 L m-2 h-1. In addition, the separation flux and efficiency remain stable during the 30 separated oil/water separation tests, exhibiting excellent recyclability.

Mechanically Durable, Highly Conductive, and Anticorrosive Composite Fabrics with Excellent Self-Cleaning Performance for High-Efficiency Electromagnetic Interference Shielding.

Metal-based materials have been widely used for the electromagnetic interference (EMI) shielding due to their excellent intrinsic conductivity. However, their high density, poor corrosion resistance, and poor flexibility limit their further application in aerospace and flexible electronics. Here, we reported a facile means to prepare lightweight, mechanically durable, superhydrophobic and conductive polymer fabric composites (CPFCs) with excellent electromagnetic shielding performance. The CPFC could be fabricated by three steps: (1) the polypropylene (PP) fabric was coated by a polydopamine (PDA) layer; (2) PP/PDA adsorbed the Ag precursor that was then chemically reduced to Ag nanoparticles (AgNPs); (3) PP/PDA/AgNPs fabrics were modified by one layer of polydimethylsiloxane (PDMS). The contact angle (CA) of the CPFCs could reach ∼152.3° while the sliding angle (SA) was as low as ∼1.5°, endowing the materials with excellent self-cleaning performance. Thanks to the extremely high conductivity of 81.2 S/cm and the unique porous structure of the fabric, the CPFC possessed outstanding EMI shielding performance with the maximum shielding effectiveness (SE) of 71.2 dB and the specific shielding effectiveness (SSE) of 270.7 dB cm3 g-1 in the X band. The interfacial adhesion is remarkably improved owing to the PDMS layer, and the superhydrophobicity, conductivity and EMI SE of CPFCs are almost maintained after cyclic abrasion and winding test. Also, the CPFCs can be used in a harsh environment, due to their excellent water proof property.

Ultrasonication assisted preparation of carbonaceous nanoparticles modified polyurethane foam with good conductivity and high oil absorption properties.

In this work, we report a facile, low cost and time-saving method for the fabrication of compressible, electrically conductive, oil absorptive, cost-effective and flexible polyurethane (PU) foam through ultrasonication induced carbonaceous nanoparticles (CNP) onto flexible PU foam (CNP-PU foam). SEM images showed that the CNP could be firmly anchored onto the PU foam, and made the PU foam surface much rougher. Zero-dimensional carbonaceous nanoparticles were easier to anchor onto the PU foam surface than one-dimensional nanoparticles (e.g., carbon nanotube) or two-dimensional nanoparticles (e.g., graphene oxide). The CNP-PU foam exhibited excellent elasticity and high mechanical durability even when it was subjected to 500 cyclic compression. The CNP-PU foam had excellent absorption of organic solvents up to 121 times the weight of the initial PU foam. In addition, the electrical conductivity of PU foams was considerably increased with the anchoring of CNP onto the matrix. In addition, compression experiments confirmed that the electrical conductivity of CNP-PU foams changed with their compression ratios, thus exhibiting excellent pressure sensitivity. The as-prepared materials have significant potential as oil absorbents, elastic conductors, flexible electrodes, pressure sensors, etc.