Search

Efficient and durable thermal insulators combined with flame resistance are required for energy efficient buildings. Here, we fabricate poly(p-phenylene benzobisoxazole) (PBO) nanofiber aerogels (PBOAs) through a proton-consumption-induced gelation of PBO nanofiber sol and a controlled freeze-drying with a low cooling rate, followed by thermal cross-linking. Nanofibrous networks based on physical entanglement of nanofibers and chemical cross-linking at the junctions were obtained, leading to ultralow density (3.6-15.7 mg cm-3), high porosity (98.9-99.7%), high specific surface area (155.4 m² g-1), low thermal conductivity (26.2-37.7 mW m-1 K-1) and superelasticity under an ultimate strain of 99%. More importantly, the aerogels achieve an excellent thermal stability, including a high decomposition temperature of 650 °C and a high long-term use temperature of 350 °C. Furthermore, the PBOAs are characterized by outstanding flame resistance, reach the nonflammable level in vertical burning tests (UL-94, V-0 class), and show a limiting oxygen index (LOI) as high as 52.8%. The aerogels cannot be ignited under simulated real-scale fire conditions, leaving suppressed smoke emission and reduced potential for flame spread and fire hazards. High thermal insulation and resistance to a 1000 °C flame has been achieved by compositing PBOAs with fumed silica. Thus, the PBOAs have promising applications in energy efficient areas, such as buildings, aerospace and many other fields, especially under harsh conditions. [ABSTRACT FROM AUTHOR]

It was found that CO2 could induce the gelation of Pluronic aqueous solutions, during which the microstructure of the solution transforms from randomly dispersed spherical micelles to cubic close packed micelles. The gelation switched by compressed CO2 has many advantages and can be applied in the synthesis of porous materials. [ABSTRACT FROM AUTHOR]

Mesoporous polymers with tunable large mesopores and thin mesopore walls were synthesized through a CO2-swollen micelle templating route. The mesopore size and porosity properties of the polymers can be easily modulated by adjusting CO2 pressure. The as-synthesized mesocellular polymers are excellent candidate supports for preparing heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

In this work we prepared icosahedral gold particles using hydrogen tetrachloroaurate(iii) hydrate (HAuCl4·3H2O) as precursor and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers as both reductant and directing agent. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and UV–Vis spectroscopy. The effects of temperature, reaction time, concentration of the precursor, and structure and concentration of the copolymers on the morphology and size of the gold particles were investigated. It was demonstrated that icosahedral gold nanoparticles can be formed under a wide range of experimental conditions and the size of the obtained icosahedral particles can be tuned from 100 nm to 1 μm by varying experimental conditions. This method has some obvious advantages, such as being simple and green, and the particle size can be easily controlled. [ABSTRACT FROM AUTHOR]

In this work, the effect of CO2 on the cloud point temperature (CPT) of an aqueous solution of p-tert-octylphenoxy polyethylene (Triton X-100) was studied at different temperatures, pressures and surfactant concentrations. It was demonstrated that CO2 could reduce the CPT of the micellar solutions considerably. On the basis of this finding, we proposed a new route to separate different substances from water by combination of Triton X-100 and CO2. It was discovered that phenol or vanadium ion in aqueous solutions could be separated efficiently from water by combination of CO2 and Triton X-100. Our study also showed that the gold nanoparticles synthesized in Triton X-100 micellar solutions could be recovered using CO2 while the surfactant remained in the solution. This is attractive because recovery of gold nanoparticles is very convenient. This separation method has some unusual advantages, such as high separation efficiency, simple post-treatment process, and lower separation temperature, which is especially advantageous when temperature-sensitive substances are involved. [ABSTRACT FROM AUTHOR]

Mesoporous polyacrylamides (PAMs) with tunable porosities were synthesized in 1-alkyl-3-methylimidazolium tetrafluoroborates ([Cnmim][BF4], n = 4, 6, 8, 10). The as-synthesized PAM was used as a support for Pd nanoparticles and the Pd/PAM composite showed high catalytic activity and selectivity for the hydrogenation of p-chloronitrobenzene reaction to yield p-chloroaniline. [ABSTRACT FROM AUTHOR]

CO2can be used to separate surfactant and organic solvent completely in various surfactant/solvent solutions without contaminating the surfactants and solvents. We believe that the simple, efficient, and greener method has wide applications. [ABSTRACT FROM AUTHOR]

Here we found that CO2has high solubility in low-cost hydrocarbon surfactant liquids. [ABSTRACT FROM AUTHOR]

Monodisperse hollow silica spheres of uniform size and ordered mesoporous shells have been successfully fabricated in water/heptane/CTAB nanoemulsions induced by compressed CO2. [ABSTRACT FROM AUTHOR]

The hydrophobic IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) can be dispersed in hydrophilic IL propylammonium formate (PAF) with the aid of surfactant AOT, and [bmim][PF6]-in-PAF microemulsions are formed. [ABSTRACT FROM AUTHOR]