Surface Hydrophobic Characteristics Research Articles

Improving the Mechanical, Thermoelectric Insulations, and Wettability Properties of Acrylic Polymers: Effect of Silica or Cement Nanoparticles Loading and Plasma Treatment.

The acrylic polymer composites in this study are made up of various weight ratios of cement or silica nanoparticles (1, 3, 5, and 10 wt%) using the casting method. The effects of doping ratio/type on mechanical, dielectric, thermal, and hydrophobic properties were investigated. Acrylic polymer composites containing 5 wt% cement or silica nanoparticles had the lowest abrasion wear rates and the highest shore-D hardness and impact strength. The increase in the inclusion of cement or silica nanoparticles enhanced surface roughness, water contact angle (WCA), and thermal insulation. Acrylic/cement composites demonstrated higher mechanical, electrical, and thermal insulation properties than acrylic/silica composites because of their lower particle size and their low thermal/electrical conductivity. Furthermore, to improve the surface hydrophobic characteristics of acrylic composites, the surface was treated with a dielectric barrier discharge (DBD) plasma jet. The DBD plasma jet treatment significantly enhanced the hydrophobicity of acrylic polymer composites. For example, the WCA of acrylic composites containing 5 wt% silica or cement nanoparticles increased from 35.3° to 55° and 44.7° to 73°, respectively, by plasma treatment performed at an Ar flow rate of 5 L/min and for an exposure interval of 25 s. The DBD plasma jet treatment is an excellent and inexpensive technique for improving the hydrophobic properties of acrylic polymer composites. These findings offer important perspectives on the development of materials coating for technical applications.

Efficient olefin epoxidation with high turnover rates over ordered mesoporous silica nanoparticles with uniform manganese sites

Olefin epoxidation has been studied over a series of mesoporous manganese silicate nanoparticles and tBuOOH. Partial substitution of Si by Mn in silica framework leads to highly dispersed, distorted Mn(III) sites, confirmed by various physicochemical analyses. High conversion and stable styrene oxide, stilbene oxide and epoxy cyclohexane yield have been achieved with MS75 with 1:1.5 ratio of olefin: oxidant. However, at faster reaction rates lower styrene oxide yield is observed at lower Mn-containing catalyst (MS100). High TON, TOF over manganese sites shows accessible monomeric Mn sites. Attributed to high reactant density at redox-active Mn silicate sites due to facile diffusion across shallow pore depth channels of nanoparticulate om-MSx and surface hydrophobic characteristics. The catalysts were found to be stable under recycling and filtration experiments. The excellent stability against leaching of active manganese species indicates stable sites and good textural properties in om-MSx, essential for extended activity.

Polydopamine/poly(sulfobetaine methacrylate) Co-deposition coatings triggered by CuSO4/H2O2 on implants for improved surface hemocompatibility and antibacterial activity

Implanted biomaterials such as medical catheters are prone to be adhered by proteins, platelets and bacteria due to their surface hydrophobicity characteristics, and then induce related infections and thrombosis. Hence, the development of a versatile strategy to endow surfaces with antibacterial and antifouling functions is particularly significant for blood-contacting materials. In this work, CuSO4/H2O2 was used to trigger polydopamine (PDA) and poly-(sulfobetaine methacrylate) (PSBMA) co-deposition process to endow polyurethane (PU) antibacterial and antifouling surface (PU/PDA(Cu)/PSBMA). The zwitterions contained in the PU/PDA(Cu)/PSBMA coating can significantly improve surface wettability to reduce protein adsorption, thereby improving its blood compatibility. In addition, the copper ions released from the metal-phenolic networks (MPNs) imparted them more than 90% antibacterial activity against E. coli and S. aureus. Notably, PU/PDA(Cu)/PSBMA also exhibits excellent performance in vivo mouse catheter-related infections models. Thus, the PU/PDA(Cu)/PSBMA has great application potential for developing multifunctional surface coatings for blood-contacting materials so as to improve antibacterial and anticoagulant properties.

Product evaluation of hydrothermal carbonization of biomass: semi-continuous vs. batch feeding

Interest in hydrothermal carbonization (HTC) is increasing worldwide due to its outstanding capabilities. This study introduces a novel semi-continuous feeding system to feed the biomass slurry against the high pressure of an HTC reactor. As expected in a semi-continuous operation, the biomass would be instantaneously exposed to the desired pressure and temperature, instead of a gradual increase to the desired temperature. Higher degrees of carbonization, lower cellulose crystallinity, improved hexagonal graphene sheets, surface hydrophobic characteristics, and higher thermal stability were observed at elevated temperatures in products from semi-continuous HTC when compared with products from batch operation. Reaction pathways were proposed for both batch and semi-continuous operations on the basis of physical and chemical characterization results. For HTC at 260 °C, the proposed semi-continuous system showed approximately 3% higher carbon content in the obtained hydrochar and a 25-min reduction in required time to reach 260 °C. The promising conclusion of these results is that by introducing continuous systems in HTC, not only will the time of the process cycle decrease, it will also achieve higher degrees of carbonization.

Fabrication and photoelectrocatalytic performance of C3N4-modified Ti/PbO2 anode with surface hydrophobicity

Reasonable hydrophobic anode is deemed to be a promising electrode for photoelectrocatalytic degradation of wastewater. In this study, the C3N4-modified Ti/PbO2 electrode with tunable hydrophobic characteristics is fabricated by a facile electrodeposition process. It is found that the introduction of C3N4 into the PbO2 films changed the morphology, surface hydrophilicity, and hydrophobicity of the electrode, which promotes the photoelectrochemical active areas, generating efficiency of hydroxyl radicals. In addition, introducing C3N4 into PbO2 coating can enhance oxygen evolution potential and carrier density of PbO2. Photoelectrocatalytic degradation experiments show that the addition of C3N4 can further improve the catalytic performance of PbO2 and there exists a significant photoelectric synergism in photoelectrocatalytic process. These results demonstrate that the combination of reasonable surface hydrophobic characteristics and photoelectrocatalytic is a prospective approach for wastewater treatment.

Surface properties and blood compatibility of some aliphatic/aromatic polyimide blends

AbstractTwo binary polyimide (PI) blends having a common monomer, diamine and dianhydride, were prepared. The first system was composed of PIs obtained from an alicyclic and flexible dianhydride, namely 5‐(2,5‐dioxotetrahydrofurfuryl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride (DOCDA) and two aromatic diamines, 4,4′‐oxydianiline (ODA) and p‐phenylenediamine (PPD), respectively. In the second system, ODA was combined with DOCDA and (hexafluoroisopropyldiene)diphtalic dianhydride (6FDA). Incorporation of aliphatic and asymmetric DOCDA moieties, hexafluoropropyldiene groups and ether linkages in the molecular structure of PI blends, poly(DOCDA/PPD)/poly(DOCDA‐ODA) and poly(6FDA‐ODA)/poly(DOCDA‐ODA) influenced the surface tension parameters, surface and interfacial free energy, and the work of spreading of water, maintaining the surface hydrophobic characteristics of both systems. In addition, it has been found out that surface hydrophobicity and surface roughness are properties that can be correlated with the red blood cells and platelets compatibility. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Characterization of Microbacterium sp. F10a and its role in polycyclic aromatic hydrocarbon removal in low-temperature soil

A polycyclic aromatic hydrocarbon degrading bacterium isolated from oil-polluted soil was identified as Microbacterium sp. F10a based on 16S rDNA gene sequence analysis. Plant growth promoting characteristics of the strain, degradation rate of phenanthrene and pyrene, and cell surface hydrophobicity characteristics of the strain were further characterized. The strain was also evaluated for promoting the growth of wheat and phenanthrene and pyrene removal from soil artificially contaminated with a mixture of phenanthrene (200 mg.kg-1) and pyrene (150 mg.kg-1) in pot experiments. The strain had the plant growth promoting characteristics of producing indole acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase activity and solubilizing inorganic phosphate. The strain also has a cell surface hydrophobicity that could increase the aqueous polycyclic aromatic hydrocarbon solubility. High-performance liquid chromatographic analysis showed that the degradation rates of phenanthrene (50 mg.L-1) and pyrene (20 mg.L-1) were 98% and 65%, respectively, under 28 degrees C after 7 days. Inoculation with the strain was found to significantly increase (p < 0.05) the growth of wheat and phenanthrene and pyrene removal in the unplanted or planted soils in a low-temperature environment. There were no significant differences in culturable bacterial numbers between live bacterial inoculation and dead bacterial inoculation controls in the unplanted and planted soils. However, the numbers of polycyclic aromatic hydrocarbon degrading bacteria were significantly greater in the inoculated planted or unplanted soils compared with the dead bacterial inoculation controls.

Characteristics of an endophytic pyrene-degrading bacterium of Enterobacter sp. 12J1 from Allium macrostemon Bunge

One pyrene-degrading endophytic bacterium was isolated from plants grown in polycyclic aromatic hydrocarbon-contaminated soils and identified as Enterobacter sp. 12J1 based on the 16S rDNA gene sequence analysis. Heavy metal and antibiotic resistance, degradation of pyrene, solubilization of inorganic phosphate and cell surface hydrophobicity characteristics of the isolate were further characterized. The isolate was also evaluated for promoting plant growth of wheat and maize and pyrene removal from pyrene-amended soil in pot experiments. High-performance liquid chromatograph (HPLC) analysis showed that the degradation rate of pyrene (5 mg l −1) by the endophytic bacterial strain 12J1 was 83.8% under 28 °C for 7 days. The Enterobacter sp. 12J1 could produce indole acetic acid (IAA), siderophore and solubilize inorganic phosphate. The Enterobacter sp. 12J1 also has a cell surface hydrophobicity. In the live bacterial inoculation experiment, an increase in pyrene removal varying from 60% to 107% was observed in the planted soils treated with 100 mg kg −1 of pyrene compared with the unplanted soils. The rate of pyrene removal increased by 43–65% in the live bacterium-inoculated planted soils compared with the dead bacterium-inoculated planted soils. Although there were no significant differences in the total culturable bacterial numbers between live and dead bacterial inoculation, the numbers of pyrene-degrading bacteria were significantly greater in the live bacterium-inoculated planted or unplanted soils. The isolate could colonize the tissue (root and stem) interiors and rhizosphere soils of wheat and maize after root inoculation.

Cell surface hydrophobicity and slime production of Staphylococcus epidermidis Brazilian isolates.

The cell surface hydrophobicity of 60 isolates and three reference strains of Staphylococcus epidermidis was assayed by means of bacterial aggregation in liquid broth, phosphate-buffered saline, and in ammonium sulfate, as well as by affinity of the bacteria to n-hexadecane and polystyrene surfaces. In order to better characterize the isolates, the influence of bacterial growth time and enzyme treatment on cell hydrophobicity and the analysis of the slime production were also investigated. The strains presented the following profiles when assayed by the ammonium sulfate aggregation test (SAT): SAT < 1M, SAT 1M - <2M, SAT 2M - <4M, and SAT >or=4M. When SAT < 1M, the strains showed positive results for most of the cell surface hydrophobicity tests. None of the strains belonging to the groups with SAT >or= 1M showed spontaneous aggregation (SA), auto-aggregation (AA), or glass adherence, albeit 32 (62.7%) strains were polystyrene adherent and 42 (82.3%) presented weak adherence to n-hexadecane (>20%). The best correlation of the results was found among the AA and glass adherence tests (100%), followed by SA/ glass adherence (98%) and SA/ AA test (98%). The polystyrene adherence test and microbial adherence to n-hexadecane test (MATH) showed 78% correlation. Proteinase K treatment reduced bacterial adherence to polystyrene, but did not influence the SAT values. Three distinct groups of strains were distinguished by the polystyrene micromethod and glass tube adherence assay: 0.0-0.4 O.D. group, including non-glass adherent isolates; 0.5-0.7 O.D. group, including strains with variable profiles (adherent or non-adherent); and 0.8-1.3 O.D. group, composed of glass-adherent strains. Evaluation by a single method seemed not to reliably determine the surface hydrophobicity characteristics of S. epidermidis clinical isolates. Auto-aggregation properties of the strains that adhered to glass seemed related to slime expression, rather than cell surface hydrophobicity. Data also suggested involvement of protein components in adherence to polystyrene, but not in auto-aggregation properties assayed by SAT.

The influence of different concentrations of melatonin on the cell surface hydrophobic characteristics of Neisseria meningitidis.

The cell surface hydrophobicity of micro-organisms is a characteristic that has been associated with the colonization of mammalian epithelia and with their capacity to induce diseases. Melatonin is a hormone produced by the pineal gland that affects the immune response mechanism. This study investigated, as an expression of the virulence of Neisseria meningitidis, how its hydrophobic characteristics were affected by exposure to increasing concentrations of melatonin. An increase in the cell surface hydrophobicity of N. meningitidis was found at concentrations of 1 mmol l(-1), while lower concentrations of melatonin did not significantly affect this particular cell surface characteristic of the micro-organism. It may be concluded that melatonin clearly influences the cell surface hydrophobicity of N. meningitidis, a circumstance that should be taken into account in future studies to determine whether this hormone plays a role in the variable pathogenicity of the bacteria in different hosts.