Effect of Hydrophobicity and Temperature on the Interactions in the Mixed Micelles of Triblock Polymers [(EO76PO29EO76) and (EO19PO69EO19)] with Monomeric and Gemini Surfactants

The interactions in the mixed micelles of two triblock polymers, F68 (EO₇₆PO₂₉EO₇₆) and P123 (EO₁₉PO₆₉EO₁₉), with a series of monomeric (dodecyltrimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide) and gemini {dimethylene bis(alkyldimethyl ammonium bromide), m-2-m, where m = 10, 12 and 14} cationic surfactants were studied by surface tension and viscosity measurements in aqueous solutions at different temperatures. The mixed micellar and interfacial properties of the binary mixtures were analyzed using Clint, Rubingh, Rosen and Maeda approaches. Both F68 and P123 show weak interactions with the studied cationic surfactants at 298.15 K which become favorable (synergistic) at higher temperatures. Further, the synergistic interactions are more in mixtures of P123 than F68 at higher temperatures. A comparison of the effects of number of EO and PO blocks in triblock polymers on various physicochemical parameters of the mixed micelles has also been made. The unfavorable enthalpy changes are compensated by favorable entropy changes as a result of the hydrophobic effect. The relative viscosity (η _r) studies show that the size of the micelles formed by pure P123 is smaller than those of F68. The values of η _r for the mixed micelles of F68 show significant variation with chain length of gemini surfactants whereas no such effect is seen in mixtures with P123.     

Enhanced conductivity of polyaniline in the presence of nonionic amphiphilic polymers and their diverse morphologies

Poly(ethylene oxide) (PEO) and its copolymers have excellent affinity for protons and contribute to proton transfer. In the present study, PEO and its copolymers, poly[(ethylene oxide)₂₀‐(propylene oxide)₇₀‐(ethylene oxide)₂₀] (EO₂₀PO₇₀EO₂₀, P123) and poly[(ethylene oxide)₁₀₆‐(propylene oxide)₇₀‐(ethylene oxide)₁₀₆] (EO₁₀₆PO₇₀EO₁₀₆, F127), have been found to significantly enhance the conductivity of polyaniline (PANI). After introducing these polymers, the conductivity of PANI is markedly promoted more than two orders of magnitude compared to that of PANI without additives, from 5.2 to 667 S/m. The molecular weight of PEO affects the conductivity of PANI/PEO. The mechanism by which these amphiphilic polymers are beneficial to the conductivity of PANI is studied experimentally and theoretically. The PANI/P123 prepared in the presence of PEO block copolymer shows gradually varying morphologies containing leaflike sheets, rodlike particles, and uniform chestnutlike sphere particles. This is similar to the morphology change of micelles with surfactant concentration. PEO, P123, and F127 are further found to have a positive effect on PANI as a material for sensors or supercapacitors, since high specific capacity and fast response rate are desired qualities in sensors and supercapacitors. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45547.     

Review on the key controls of designer copolymer-silica mesophase monoliths (HOM-type) with large particle morphology,ordered geometry and uniform pore dimension

This review introduces the extensive key factors of the design of mesostructured monoliths with two- and three-dimensional (2D and 3D) geometries and large particle morphologies. Simple strategy in terms of fabrication time (within 10 min) and composition phase domains was achieved by using an instant direct-templating method of lyotropic and microemulsion phases of a variety of triblock copolymer (EO_m-PO_n-EO_m) surfactants, as we recently reported in [33] and [34]. The synthetic strategy provides realistic control over a wide range of mesophase geometries, yet maintains the long-range structural ordering, and thus improved the simplicity, significant periodicity, and high uniformity of the resultant silica monoliths. Cubic mesophases, in particular, exhibit a wide variety of mesostructured geometries when the block copolymers were used as a structure-directing agent under acidic synthesis conditions. For example, triblock copolymer (P123, EO₂₀PO₇₀EO₂₀) was used to fabricate 2D hexagonal (P6mm). Our synthesis protocol revealed that ordered 3D cubic (Fd3m), (Im3m), and (Ia3d) silica monoliths were also fabricated in large domain sizes by templating P123 copolymers. In general, key factors such as the degree of solubilization of the hydrocarbons (co-solvent), the copolymer concentrations used in the phase domains, and the copolymer molecular nature, such as EO/PO ratio, significantly affect the formation of mesostructured phases and their extended long-range ordering in the final replicas of the silica monolith frameworks. The remarkable structural findings of 2D and 3D frameworks, transparent monoliths, and micropores combined with large cage- and cylindrical-like mesopores might show their desirability in many applications.     

Temperature and salt-induced micellization of some block copolymers in aqueous solution

Micellization of three commercial samples of ethylene oxide (EO)-propylene oxide (PO) (PEO-PPO-PEO) triblock copolymers (pluronics) P65 (EO₂₅PO₃₀EO₂₅, mw PPO=1750, %PEO=50), P85 (EO₂₅PO₄₀EO₂₅, mw PPO=2250, %PEO=50), and F88 (EO₁₀₂PO₄₀EO₁₀₂, mw PPO=2250, %PEO=80) in aqueous sodium chloride solution (0–3 M) was examined by cloud point, surface tension, dye spectral change, fluorescence, and viscosity measurements over a temperature range of 25–50°C. Salt-induced micellization and micelle growth were observed. The presence of sodium chloride enhanced hydrophobicity in the PPO moiety and reduced hydrophilicity of PEO moieties, favoring micellization at relatively lower concentrations than in water at ambient temperature. The effect of salt on micellization is similar to that of increasing temperature. The critical micelle concentrations (CMC) and critical micelle temperatures showed a marked decrease in the presence of added salt. CMC obtained by different methods were in good agreement.     

Structural Characterization of Mesoporous Silica Nanofibers Synthesized Within Porous Alumina Membranes

Mesoporous silica nanofibers were synthesized within the pores of the anodic aluminum oxide template using a simple sol–gel method. Transmission electron microscopy investigation indicated that the concentration of the structure-directing agent (EO₂₀PO₇₀EO₂₀) had a significant impact on the mesostructure of mesoporous silica nanofibers. Samples with alignment of nanochannels along the axis of mesoporous silica nanofibers could be formed under the P123 concentration of 0.15 mg/mL. When the P123 concentration increased to 0.3 mg/mL, samples with a circular lamellar mesostructure could be obtained. The mechanism for the effect of the P123 concentration on the mesostructure of mesoporous silica nanofibres was proposed and discussed.     

Properties of a Binary System Containing Anionic and Cationic Gemini Surfactants

Surface tension, fluorescence, and dynamic light scattering were used to investigate the properties of a binary surfactant system comprising an anionic gemini surfactant (DLMC) and cationic gemini surfactant (II‐12‐EO₂). Surface tension measurements afforded the critical micelle concentration (cmc) of the mixture and the values are all lower than those of pure constituent surfactants. For the mixtures of II‐12‐EO₂/DLMC, the micelle aggregation number decreases with the increase of II‐12‐EO₂, and the micropolarity of the micelle is lowest when the molar fraction of II‐12‐EO₂ is 0.5; the hydrodynamic radius (R_h) of the mixed micelle first increases and then decreases with the addition of II‐12‐EO₂, and larger micelles are obtained when the molar fraction of II‐12‐EO₂ is 0.5 or 0.7.     

Preparation and electrochemical performance studies on Cr-doped Li3V2(PO4)3 as cathode materials for lithium-ion batteries

Cr-doped Li₃V_2−xCr_x(PO₄)₃/C (x = 0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li₃V_2−xCr_x(PO₄)₃/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li₃V_2−xCr_x(PO₄)₃/C. Li₃V_1.9Cr_0.1(PO₄)₃/C compound presents an initial capacity of 171.4 mAh g⁻¹ and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li₃V_1.9Cr_0.1(PO₄)₃/C can give an initial capacity of 130.2 mAh g⁻¹ and 10.8% capacity loss after 100 cycles where the Li₃V₂(PO₄)₃/C presents the initial capacity of 127.4 mAh g⁻¹ and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x = 0.1) in V sites.     

The effect of iron incorporation on the in vitro bioactivity and drug release of mesoporous bioactive glasses

Magnetic mesoporous bioactive glasses with the composition xFe–(80−x)SiO₂–15CaO–5P₂O₅ (mol%) (Fe/MBGs) were prepared by the non-ionic block copolymer EO₂₀PO₇₀EO₂₀ (P123) surfactant as template and the evaporation-induced self-assembly process using Ca, P, Si and Fe sources. The structure, morphology and magnetic properties of Fe/MBGs were characterized by X-ray diffraction, scanning electron microscopy, infrared spectra, vibrating sample magnetometer and N₂ adsorption–desorption technique. The results show that Fe/MBGs have porous network (pore diameter of 50–100 nm), mesoporous walls (mesoporous size of 4–5 nm), and that the mesostructure, magnetic properties and in vitro bioactivity of the Fe/MBGs depend on the chemical composition. Furthermore, the Fe incorporation in the MBGs enhanced the magnetic properties, demonstrated sustained drug delivery and maintained apatite-formation ability in SBF. This means that the Fe/MBGs allowed bioactivity could improve their drug delivery capacity, thus enhancing their potential applications as bioactive filler materials for bone tissue regeneration.     

Effect of ethyleneglycol addition on the properties of P-doped NiMo/Al2O3 HDS catalysts: Part I. Materials preparation and characterization

Phosphorous-doped NiMo/Al₂O₃ hydrodesulfurization (HDS) catalysts (nominal Mo, Ni and P loadings of 12, 3, and 1.6 wt%, respectively) were prepared using ethyleneglycol (EG) as additive. The organic agent was diluted in aqueous impregnating solutions obtained by MoO₃ digestion in presence of H₃PO₄, followed by 2NiCO₃·3Ni(OH)₂·4H₂O addition. EG/Ni molar ratio was varied (1, 2.5 and 7) to determine the influence of this parameter on the surface and structural properties of synthesized materials. As determined by temperature-programmed reduction, ethyleneglycol addition during impregnation resulted in decreased interaction between deposited phases (Mo and Ni) and the alumina carrier. Dispersion and sulfidability (as observed by X-ray photoelectron microscopy) of molybdenum and nickel showed opposite trends when incremental amounts of the organic were added during catalysts preparation. Meanwhile Mo sulfidation was progressively decreased by augmenting EG concentration in the impregnating solution, more dispersed sulfidic nickel was evidenced in materials synthesized at higher EG/Ni ratios. Also, enhanced formation of the so-called “NiMoS phase” was registered by increasing the amount of added ethyleneglycol during simultaneous Ni–Mo–P–EG deposition over the alumina carrier. That fact was reflected in enhanced activity in liquid-phase dibenzothiophene HDS (batch reactor, T = 320 °C, P = 70 kg/cm²) and straight-run gas oil desulfurization (steady-state flow reactor), the latter test carried out at conditions similar to those used in industrial hydrotreaters for the production of ultra-low sulfur diesel (T = 350 °C, P = 70 kg/cm², LHSV = 1.5 h⁻¹ and H₂/oil = 2500 ft³/bbl).     

Preparation of Zircon-Encapsulated Carbon Black Ceramic Pigment Using the Collapsed Mesoporous-Structure

The black zircon encapsulated carbon black (C@ZrSiO₄) ceramic pigment is prepared using the collapsed mesoporous-structure to improve the coverage of carbon black. In the preparation process, the tri-block copolymer (Pluronic P123, EO₂₀PO₇₀EO₂₀) is used as both the template of mesoporous zirconia and the source of carbon black under the calcination at 300 °C in Ar. Carbon black originated from P123 distributes uniformly in the mesoporous zirconia. After mixed with SiO₂ sol and re-calcinated at over 800 °C, the procedure loses gradually the mesoporous structure and reacts with SiO₂ to generate zircon. Carbon black is encapsulated completely by dense zircon. After calcined at 900 °C in air to remove the possible uncoated carbon black, the obtained pigment still has the deep black hue (L* = 24.14). This preparation method provides a simple way to prepare black ceramic pigment.

     

Promotional effect of gold added to palladium supported on a new mesoporous TiO2 for total oxidation of volatile organic compounds

Gold and palladium were supported on a mesoporous TiO₂ for total oxidation of volatile organic compounds (VOCs). Mesoporous high surface area titania support was synthesised using of Ti(OC₂H₅)₂ in the presence of CTMABr surfactant. After removing the surfactant molecules, 0.5 or 1.5 wt% of palladium and 1 wt% of gold were precipitated on the support by, respectively, wet impregnation and deposition–precipitation methods. The activity for toluene and propene total oxidation of the prereduced samples follows the same order: 0.5%Pd-1%Au/TiO₂ > 1.5%Pd/TiO₂ > 0.5%Pd/TiO₂ > 1%Au-0.5%Pd/TiO₂ > 1%Au/TiO₂ > TiO₂. Moreover, a catalytic comparison with samples based on a conventional TiO₂, shows the catalytic advantage of the mesoporous TiO₂ support. The promotional effect of gold added to palladium could be partly explained by small metallic particles (TEM), but meanly by metallic particles made up of Au-rich core with a Pd-rich shell. Moreover, the hydrogen TPR profile of 0.5%Pd-1%Au/TiO₂ shows only the signal attributed to small PdO particles. Gold also implies a protecting effect of the support under reduction atmosphere. Operando diffuse reflectance infrared fourier transform (DRIFT) spectroscopy was carried on and allowed to follow the VOCs oxidation and the formation of coke molecules, but also a metallic electrodonor effect to the adsorbed molecule which increases in the same order as the activity for oxidation reaction. The presence of coke after test was also shown by DTA–TGA by exothermic signals between 300 and 500 °C and by EPR (g = 2.003).     

Catalytic applications of sulfonic acid functionalized mesoporous organosilicas with different fraction of organic groups in the pore wall

Organosulfonic acid functionalized mesoporous organosilicas with different fraction of organic groups in the pore wall was synthesized in the presence of P123 (EO₂₀PO₇₀EO₂₀) by controlling the molar ratio of tetramethoxysilane (TMOS) to 1,2-bis(trimethoxysilyl)ethane (BTME) in the initial mixture during the co-condensation process of silane precursors in acidic medium. Structural characterizations (X-ray diffraction, nitrogen sorption analysis, and transmission electron microscopy) show that all materials have ordered hexagonal mesoporous structure with large pore diameter (7–9 nm). The existence of ethane and sulfonic acid groups in the material was verified by ²⁹Si MAS and ¹³C CP MAS NMR and X-ray photoelectron spectroscopy (XPS). The mesoporous solid acids can adsorb both water and hexane (the adsorption capacity for water and hexane is 240 and 600 mg/g, respectively) due to the existence of surface hydroxyl groups, propyl sulfonic acid group, and the ethane moiety. These mesoporous solid acids are efficient catalysts for the dehydration of 1-butanol and the hydration of propylene oxide (PO).     

Aggregation of Alcohols Ethoxylates in n-Heptane

The solubility and aggregation process of polyethoxylated non-ionic surfactants, of general formula C _i H_2i+1–(O–CH₂–CH₂) _j –OH with i = 6, 8, 10 and j = 3–6 (C _i EO _j ), in heptane were studied. The aggregation of C _i EO _j surfactants in heptane was investigated by using methylene blue (MB) as an absorption probe. In solutions of MB in the presence of these surfactants in heptane, at concentrations larger than the re-dissolution concentration, the UV bands associated to free MB (A ₁) and MB–EO complex (A ₂) were detected. The ratio of these intensities A ₂/A ₁, was used to study the kinetics of the complex formation in pure surfactant. The value of A ₂/A ₁ depends on the surfactant structure and the media wherein MB is dissolved, being larger in the pure surfactant than in heptane solutions. These results are explained in terms of solvent effect and aggregate structures on the complex formation.

Hydrothermal transformation of a layered aluminophosphate into a mesoporous structure

A new mesoporous aluminophosphate (AlPO₄) has been synthesized through hydrothermal transformation of a lamellar mesostructured aluminophosphate prepared in the presence of a neutral surfactant dodecylamine (DDA) under mild alkaline pH conditions and using water–ethanol mixture as the synthesis medium. Post-synthesis hydrothermal treatment was carried out at 448 K for 72 h in the presence of dilute aqueous phosphoric acid, which results this phase transformation. Lamellar and mesoporous phases of these samples were revealed from powder X-ray diffraction, SEM-EDS, transmission electron microscopic image analysis, ³¹P MAS NMR a FT IR spectroscopic studies and thermal analysis. N₂ sorption studies revealed the existence of pores with dimension of small mesopores after H₃PO₄ treatment. Pillaring of the interlayers through PO₄ units during post-synthesis hydrothermal treatment could be responsible for the transformation of lamellar to mesoporous phase.     

A novel sol–gel synthesis of mesoporous ZrO2–MoO3/WO3 mixed oxides

Mesoporous ZrO₂–MoO₃/WO₃ mixed oxides have been synthesized through a novel, convenient one step sol–gel technique. Water soluble molybdate/tungstate and zirconium (IV) carbonate complex have been employed in presence of cationic surfactant, tetradecyltrimethylammonium bromide under basic condition. The synthesized materials have shown high specific surface areas and narrow pore-size distributions which were achieved after optimization of the amount of surfactant. Mesoporous ZrO₂–MoO₃ and ZrO₂–WO₃ mixed oxides have shown specific surface areas of 228 and 275 m² g⁻¹ and pore sizes of 3.65 nm and 4.33 nm, respectively. FTIR and Raman studies prove the formation of hetero bonding in mixed oxides.     

Novel composite polymer electrolyte comprising poly(ethylene oxide) and triblock copolymer/mesostructured silica hybrid used for lithium polymer battery

Ordered mesoporous materials, due to its potential applications in catalysis, separation technologies, and nano-science have attracted much attention in the past few years. In this work, a novel PEO-based composite polymer electrolyte by using organic-inorganic hybrid EO₂₀PO₇₀EO₂₀ @ mesoporous silica (P123 @ SBA-15) as the filler has been developed. The interactions between P123 @ SBA-15 hybrid and PEO chains are studied by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and FT-IR techniques. The effects of P123 @ SBA-15 on the electrochemical properties of the PEO-based electrolyte, such as ionic conductivity, lithium ion transference number are studied by electrochemical ac impedance spectroscopy and steady-state current method. The experiment results show that P123 @ SBA-15 can enhance the ionic conductivity and increase the lithium ion transference number of PEO-based electrolyte, which are induced by the special topology structure of P123 in P123 @ SBA-15 hybrid, at the same time. The excellent lithium transport properties and broad electrochemical stability window suggesting that PEO-LiClO₄/P123 @ SBA-15 composite polymer electrolyte can be used as candidate electrolyte materials for lithium polymer batteries.     

Self-organization of stack-up block copolymers into polymeric supramolecules

Polyethylene oxide –b– polypropylene oxide -b- polyethylene oxide (EO₁₀₆PO₇₀EO₁₀₆) block copolymer self-organizes into polymeric supramolecules, characterized by NMR as phase transition from the isotropic stack-up block structure to the ordered cubic polymeric supramolecular structure. Its dependence on both temperature and copolymer concentration is clearly shown by the changes in line shape and chemical shift of the PO₇₀ block β, γ resonances.     

Influence of reaction products of K-getter fuel additives on commercial vanadia-based SCR catalysts: Part I. Potassium phosphate

Commercial vanadia-based full-length monoliths have been exposed to aerosols formed by injection of K₃PO₄ (dissolved in water) in a hot flue gas (T > 850 °C) from a natural gas burner. Such aerosols may form when burning fuels with high K- and P-content, or when P-compounds are mixed with biomass as a K-getter additive. The formed aerosols have been characterized by using both a SMPS system and a low pressure cascade impactor, showing a dual-mode volume-based size distribution with a first peak at around 30 nm and a second one at diameters >1 μm. The different peaks have been associated with different species. In particular, the particles related to the 30 nm peak are associated to condensed phosphates, whereas the larger particles are associated to potassium phosphates. Two monoliths have been exposed during addition of 100 and 200 mg/Nm³ K₃PO₄ for 720 and 189 h, respectively. Overall, deactivation rates up to 3%/day have been measured. The spent catalysts have been characterized by bulk chemical analysis, Hg-porosimetry and SEM-EDX. NH₃-chemisorption tests on the spent elements and activity tests on catalyst powders obtained by crushing the monoliths have also been carried out. The catalyst characterization has shown that poisoning by K is the main deactivation mechanism. The results show that binding K in K–P salts will not reduce the rate of catalyst deactivation.     

Synthesis and structure of Mu-33, a new layered aluminophosphate

Mu-33, a new layered aluminophosphate with an Al/P ratio of 0.66, was obtained from a quasi non-aqueous synthesis in which tert-butylformamide (tBF) was the main solvent and only limited amounts of water were present. During the synthesis, tBF decomposed and the resulting protonated tert-butylamine is occluded in the as-synthesized material. The approximate structure was determined from data collected on a microcrystal (200 × 25 × 5 μm³) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, but the quality of these data did not allow satisfactory refinement. Therefore the structure was refined using high-resolution powder diffraction data, also collected at the ESRF. The structure (P2₁/c, a = 9.8922(6) Å, b = 26.180(2) Å, c = 16.729(1) Å and β = 90.4(1)°) consists of anionic aluminophosphate layers that can be described as a six-ring honeycomb of alternating corner-sharing AlO₄ and PO₄ tetrahedra with additional P-atoms above and below the honeycomb layer bridging between Al-atoms. The tert-butylammonium ions and water molecules located in the interlayer spacing interact via hydrogen-bonds with the terminal oxygens of the P-atoms. The characterization of this new aluminophosphate by ¹³C, ³¹P, ¹H–³¹P heteronuclear correlation (HETCOR) and ²⁷Al 3QMAS solid state NMR spectroscopy is also reported.     

Oriented polycrystalline mesoporous CeO2 with enhanced pore integrity

Mesoporous CeO₂ particles are synthesized using a sol–gel method involving Pluronic P123 or F127 tri-block copolymer and cerium acetate hydrate. Transmission electron microscopy reveals well defined meso-channels of about 10 nm in diameter and a wall framework consisting of highly oriented polycrystalline CeO₂. The [0 0 1] axis of the crystals is found to be aligned parallel to the meso-channels, and lattice coherency of [1 0 0] or [0 1 0] also exists in perpendicular plane to the channel. A cooperative self-assembly of the tri-block copolymer and Ce⁴⁺ species is believed to occur, along with the precipitation of nano-crystalline CeO₂ in the sol–gel process. It is proposed that the preferential orientation may result from a favored linkage of the low-order Miller indices {0 0 1} planes of CeO₂ to the PEO segment in the PEO–PPO–PEO tri-block copolymer micelles. The unique structural characteristics of meso-CeO₂ appear to contribute to maintaining the pore integrity during the synthesis as well as in a post-fabrication in situ TEM heating test.