With the growth of oil production and transportation, there is greater potential for accidental oil spills. Here we fabricated a robust superhydrophobic and superoleophilic carbon nanotube/poly(dimethylsiloxane)-coated polyurethane sponge for the continuous absorption and expulsion of oils and organic solvents from water surfaces. When applied in conjunction with a vacuum system, this sponge could separate great amounts of oils-up to 35000 times its own weight-from water in a one-step process and could also separate surfactant-free water-in-oil emulsions with high efficiency (oil purity: >99.97 wt %), making it a promising candidate material for use in oil-spill cleanups.
In this paper, we report a simple and an inexpensive method for fabricating superhydrophobic/superoleophilic mesh films from microstructured ZnO coatings. The microstructured ZnO coatings, which do not contain any fluorinated compounds, maintain their superhydrophobicity and superoleophilicity after ultraviolet irradiation and display environmental stability. Furthermore, those microstructured ZnO-coated mesh films exhibit good selectivity (even underwater) and excellent recyclability, making them promising candidates for many potential applications, including liquid-liquid separation, water treatment, and liquid transportation.
Four main-chain type polybenzoxazine precursors were synthesized from the Mannich-type polycondensation of biphenol A, paraformaldehyde, and four typical aromatic diamines: 1,4-phenylenediamine, 4,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl ether, and 2,2-bis[4-(4-aminophenoxy)phenyl] propane. The solvent effect on the polycondensation was examined. We found that polybenzoxazine precursors prepared in toluene/ethanol exhibit higher purity, higher molecular weight, and lead to better thermal properties after curing than those prepared in chloroform, as recommended by Takeichi's group (T. Takeichi et al., Polymer, 2005, 46, 12172). The cured polybenzoxazine films prepared by these polybenzoxazine precursors display unusual flexibility, extremely high T-g, and low surface energy. They show T-g values as high as 272-353 degrees C (DMA data), coefficients of thermal expansion as low as 39-49 ppm/degrees C, contact angles as high as 100-102 degrees, and surface energy as low as 17.7-24.5 mJ m(-2)
How low can you go? Polybenzoxazines can display surface free energies which are even lower than that of pure poly(tetrafluoroethylene). The contact angles and surface free energies were monitored during the polymerizations (see graph for an example). These materials are cheaper to prepare and easier to process than fluoropolymers.
In this study, we report on a simple two-step casting process designed to create a stable superhydrophobic surface. This method possesses the advantages of being both simple and inexpensive as well as utilizing non-fluorine-containing compounds. Most interestingly, we found that the as-prepared surface possesses superhydrophobic properties not only for pure water but also for corrosive water under both acidic and basic conditions. Furthermore, the superhydrophobic polybenzoxazine surfaces had excellent environmental stability with regard to both heating and organic solvent treatment in terms of the contact angle to water.
In this study, we found that poly(vinyl phenol)/polybenzoxazine (PVPh/PBZ) copolymers feature low surface energies when they possess a minimal number of intermolecular hydrogen-bonding interactions. For example, PVPh/PBZ = 30/70 exhibits an extremely low surface energy of 16.8 mJ/m2 after thermal curingeven lower than that of poly(tetrafluoroethylene) (22.0 mJ/m2)based on calculations performed using a two-liquid geometric method. Infrared spectroscopic analyses indicated that a decrease in the degree of intermolecular hydrogen bonding in the PVPh/PBZ copolymers resulted in a lower surface free energy. An increase in the intermolecular hydrogen bonding did, however, enhance the thermal properties, namely, the glass-transition temperature, the thermal decomposition temperature, and the char yield. The manipulation of intermolecular hydrogen-bonding interactions is a unique and simple approach toward preparing low-surface-energy materials without the need to employ fluoropolymers or silicones.
Two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (PMMA-POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique. The miscibility and specific interaction behaviors of PMMA-POSS and PMMA with phenolic resin were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). FTIR results reveal that at least three competing equilibriums are present in the phenolic/PMMA-POSS blend: self-association of phenolic (hydroxyl-hydroxyl), hydroxyl-siloxane interassociation between phenolic and POSS, and hydroxyl-carbonyl interassociation between phenolic and PMMA. Among these blends, single and higher T g s of these phenolic/PMMA-POSS blends were observed than the corresponding phenolic/PMMA blends at same composition, revealing that a stronger interassociation interaction of hydroxyl-siloxane than the hydroxyl-carbonyl interaction. Furthermore, we also found the screening effect in phenolic/LPMMA-POSS blends that tends to significantly decrease the hydrogen bond formation of the hydroxyl-carbonyl interassociation.
The hydrophilicity of bis(3-allyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane(B-ala) polybenzoxazine film and superhydrophobic polybenzoxazine-hybrid surface can be controlled through UV exposure to change the ratio of intra- to intermolecular hydrogen bonds. A fraction of the intramolecular hydrogen bonding of the as-cured sample will convert into intermolecular hydrogen bonding upon UV exposure and thus results in an increase of hydrophilicity. This simple method allows for manipulating the hydrophilicity at selected regions on a superhydrophobic polybenzoxazine hybrid surface to create a patterned surface with superhydrophobic and superhydrophilic regions. Additionally, we have found that the superhydrophobic polybenzoxazine-silica hybrid surface exhibits good adhesion of water droplets after UV exposure, which can be served as a "mechanical hand" to transfer water droplets from a superhydrophobic surface to a hydrophilic one.
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