Stable electrically conductive, highly flame-retardant foam composites generated from reduced graphene oxide and silicone resin coatings.

To acheive flexible polyurethane (PU) foam composites with stable electrical conductivity and high flame retardancy involved first coating of graphene oxide (GO) onto PU foam surfaces and then chemically reducing the GO with hydrazine to form reduced GO (RGO). The RGO-coated PU foam is then dipped into a solution containing silicone resin (SiR) and silica nano-particles and cured. The resulting composites (PU-RGO-SiR) show superior flame retardancy, thermal stability and mechanical stability relative to the PU starting materials or PU coated with either RGO or SiR alone. The electrical conductivity of the PU-RGO-SiR composites (as high as 118 S m-1 at room temperature) could almost be retained but with small loss of 9.5% of the original value after 150 cyclic compression. When the samples were subjected to a temperature range from -50 to 400 °C, the electrical conductivity could remain constant at -50 °C, 25 °C, 100 °C, 200 °C, and even at 300 °C and 400 °C; the electrical-conductivity exhibited mild vibration but the vibration range was not beyond 5.6%. Flame retardancy tests show that the limiting oxygen index (LOI) increases from 14.7% for the pure foam to 31.5% for PU-RGO-SiR, and the PU-RGO-SiR composites exhibit a 65% reduction in the peak heat release rate (pHRR) and a 30% reduction in total smoke release (TSR). Thus, stable electrically conductive and highly flame-retardant foam composites have potential applications even in a variety of harsh conditions like high temperature, flame, organic solvents, and external compression.

Facile UV-Induced Surface Covalent Modification to Fabricate Durable Superhydrophobic Fabric for Efficient Oil-Water Separation.

In this work, a durable superhydrophobic fabric was fabricated by using a facile UV-induced surface covalent modification strategy. 2-isocyanatoethylmethacrylate (IEM) containing isocyanate groups can react with the pre-treated hydroxylated fabric, producing IEM molecules covalently grafted onto the fabric's surface, and the double bonds of IEM and dodecafluoroheptyl methacrylate (DFMA) underwent a photo-initiated coupling reaction under UV light radiation, resulting in the DFMA molecules further grafting onto the fabric's surface. The Fourier transform infrared, X-ray photoelectron spectroscopy and scanning electron microscopy results revealed that both IEM and DFMA were covalently grafted onto the fabric's surface. The formed rough structure and grafted low-surface-energy substance contributed to the excellent superhydrophobicity (water contact angle of ~162°) of the resultant modified fabric. Notably, such a superhydrophobic fabric can be used for efficient oil-water separation, for example a high separation efficiency of over 98%. More importantly, the modified fabric exhibited excellent durable superhydrophobicity in harsh conditions such as immersion in organic solvents for 72 h, an acidic or alkali solution (pH = 1-12) for 48 h, undergoing laundry washing for 3 h, exposure to extreme temperatures (from -196° to 120°), as well as damage such as 100 cycles of tape-peeling and a 100-cycle abrasion test; the water contact angle only slightly decreased from ~162° to 155°. This was attributed to the IEM and DFMA molecules grated onto the fabric through stable covalent interactions, which could be accomplished using the facile strategy, where the alcoholysis of isocyanate and the grafting of DFMA via click coupling chemistry were integrated into one-step. Therefore, this work provides a facile one-step surface modification strategy for preparing durable superhydrophobic fabric, which is promising for efficient oil-water separation.

One-Step Covalent Surface Modification to Achieve Oil-Water Separation Performance of a Non-Fluorinated Durable Superhydrophobic Fabric.

In this work, a durable superhydrophobic fabric was fabricated by a facile covalent surface modification strategy, in which the anchoring of 10-undecenoyl chloride (UC) onto the fabric through the esterification reaction and covalent grafting of n-dodecyl-thiol (DT) via thiol-ene click chemistry were integrated into one step. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurement results demonstrated that UC and DT were covalently grafted onto the fabric surface. The formed gully-like rough structure by the grafted UC and DT on the fabric surface together with the inherent microfiber structure, combined with the grafted low-surface-energy materials of UC and DT, gave the resultant modified DT-UC@fabric superhydrophobic performance. The superhydrophobic DT-UC@fabric was used for separation of oil-water mixtures; it exhibited high separation efficiency of more than 98%. In addition, it presented excellent durability against mechanical damage; even after 100 cyclic tape-peeling and abrasion tests, the DT-UC@fabric could preserve superhydrophobic performance, which was ascribed to the formed covalent interactions between the fabric surface and the grafted UC and DT. Therefore, this work provided a facile, efficient strategy for fabricating superhydrophobic composites with excellent durability, which exhibited a promising prospect in the application of self-cleaning and oil-water separation.

Room Temperature Co-Precipitation Synthesis of Magnetite Nanoparticles in a Large pH Window with Different Bases.

Magnetite nanoparticles (Fe3O4) represent the most promising materials in medical applications. To favor high-drug or enzyme loading on the nanoparticles, they are incorporated into mesoporous materials to form a hybrid support with the consequent reduction of magnetization saturation. The direct synthesis of mesoporous structures appears to be of interest. To this end, magnetite nanoparticles have been synthesized using a one pot co-precipitation reaction at room temperature in the presence of different bases, such as NaOH, KOH or (C2H5)4NOH. Magnetite shows characteristics of superparamagnetism at room temperature and a saturation magnetization (Ms) value depending on both the crystal size and the degree of agglomeration of individual nanoparticles. Such agglomeration appears to be responsible for the formation of mesoporous structures, which are affected by the pH, the nature of alkali, the slow or fast addition of alkaline solution and the drying modality of synthesized powders.

2,3,4,5-Tetraphenylsilole-based conjugated polymers: synthesis, optical properties, and as sensors for explosive compounds.

A series of linear 2,5-tetraphenylsilole-vinylene-type polymers were successfully synthesized for the first time. The tetraphenylsilole moieties were linked at their 2,5-positions through a vinylene bridge with p-dialkoxybenzenes to obtain polymer PSVB and with 3,6-carbazole to obtain polymer PSVC. For comparison, 2,5-tetraphenylsilole-ethyne-type polymer PSEB was also synthesized, in which the vinylene bridge of PSVB was replaced with an ethyne bridge. Very interestingly, the bridging group (vinylene or ethyne) had a significant effect on the photophysical properties of the corresponding polymers. The fluorescence peak of PSEB at 504 nm in solution originated from the emission of its silole moieties, whereas PSVB and PSVC emitted yellow light and no blueish-green emission from the silole moieties was observed, thus demonstrating that the emissions of PSVB and PSVC were due to their polymer backbones. More importantly, the 2,5-tetraphenylsilole-ethyne polymer exhibited a pronounced aggregation-enhanced emission (AEE) effect but the 2,5-tetraphenylsilole-vinylene polymer was AEE-inactive. Moreover, both AEE-active 2,5-tetraphenylsilole-ethyne polymer and AEE-inactive 2,5-tetraphenylsilole-vinylene polymers were successfully applied as fluorescent chemosensors for the detection of explosive compounds.