Triblock Copolymer F127 Research Articles

Successful entrapment of carbon dots within flexible free-standing transparent mesoporous organic-inorganic silica hybrid films for photonic applications

The effective entrapment of Carbon dots (CDs) into a polymer-silica hybrid matrix, formed as free standing transparent flexible films, is presented. The composite's synthesis, characterization, device application and properties -mechanical, thermal and optical- are being provided and discussed. CDs of 3nm mean size with strong photoluminescence are embedded into a silica matrix during the sol-gel procedure, using tetraethyl orthosilicate as the precursor and F127 triblock copolymer as the structure directing agent under acidic conditions. The final hybrid nanostructure forms free standing transparent films that show high flexibility and long term stable CDs luminescence indicating the protective character of the hybrid matrix. It is crucial that the photoluminescence of the hybrid's CDs is not seriously affected after thermal treatment at 550°C for 30min. Moreover, the herein reported hybrid is demonstrated to be suitable for the fabrication of advanced photonic structures using soft lithography processes due to its low shrinkage and distortion upon drying, both attributable to its porosity. Finally, it is reported that addition of F127 ethanolic solution in aqueous solution of CDs induces a blue-shift of their photoluminescence.

Flexible, cathodoluminescent and free standing mesoporous silica films with entrapped quasi-2D perovskites

The effective entrapment of hybrid organic-inorganic semiconductors (HOIS) into mesoporous polymer-silica hybrid matrices, formed as free standing flexible films, is presented for the first time. A blend of quasi-2D HOIS, simply synthesized by mixing two-dimensional (2D) and three dimensional (3D) HOIS, exhibiting strong photoluminescence, is embedded into porous silica matrices during the sol-gel synthesis, using tetraethylorthosilicate as precursor and Pluronic F-127 triblock copolymer as structure directing agent, under acidic conditions. The final nanostructure hybrid forms flexible, free standing films, presenting high cathodoluminescence and long stable excitonic luminescence, indicating the protective character of the hybrid matrix towards the entrapped perovskite. A significant result is that the photoluminescence of the entrapped HOIS is not affected even after films’ prolonged exposure to water.

Magnetic mesoporous carbon composites incorporating hydrophilic metallic nanoparticles for enrichment of phosphopeptides prior to their determination by MALDI-TOF mass spectrometry

Magnetic mesoporous carbon composites incorporating hydrophilic metallic nanoparticles were synthesized from resol, ZrO(NO3)2, ferric acetylacetonate, and triblock copolymer F127. The method involves a multi-component co-assembly strategy associated with direct carbonization. The resulting carbon material is shown to be useful as a metal oxide affinity chromatography (MOAC) material for enrichment of phosphopeptides owing to its large mesoporous (4.8 nm) surface area (442 m2 g−1), large pore volume (0.37 cm3 g−1) and excellent hydrophilicity. The metallic iron and ferric oxide particles modified on the mesoporous carbon exert a magnetic force and, in combination with the metallic zirconia, is a viable MOAC material for enrichment of low-abundance phosphopeptides. Because of metal chelation between metallic nanoparticles and the phosphate groups of phosphopeptides, the zirconia/magnetic mesoporous carbon displays high selectivity even at a phosphopeptide/nonphosphopeptide molar ratio of 1:500. As little as 1.5 fmol of phosphopeptides become detectable. The MOAC was successfully applied to the identification by MALDI-TOF MS of phosphopeptides in human serum and nonfat milk.

Incorporating poly(3-hexyl thiophene) into orthogonally aligned cylindrical nanopores of titania for optoelectronics

The incorporation of hole conducting polymer poly(3-hexyl thiophene) (P3HT) into the 8–9 nm cylindrical nanopores of titania is investigated using films with a unique orthogonally oriented hexagonal close packed mesostructure. The films are synthesized using evaporation induced self-assembly (EISA) with Pluronic triblock copolymer F127 as the structure directing agent. The orthogonally oriented cylindrical nanopore structure was chosen over a cubic structure because confinement in uniform cylindrical channels is hypothesized to enhance hole conductivity of P3HT by inducing local polymer chain ordering. Orthogonal orientation of the cylindrical nanopores is achieved by modifying the substrate (FTO-coated glass slides) with crosslinked F127. After thermal treatment to remove organic templates from the films, P3HT is infiltrated into the nanopores by spin coating a 1 wt% P3HT solution in chlorobenzene onto the titania films followed by thermal annealing under vacuum at 200 °C. The results show that infiltration is essentially complete after 30 min of annealing, with little or no further infiltration thereafter. A final infiltration depth of ∼14 nm is measured for P3HT into the nanopores of titania using neutron reflectometry measurements. Photoluminescence measurements demonstrate that charge transfer at the P3HT-TiO2 interface improves as the P3HT is infiltrated into the pores, suggesting that an active organic-inorganic heterojuction is formed in the materials.

Effects of High Pressure on Internally Self-Assembled Lipid Nanoparticles: A Synchrotron Small-Angle X-ray Scattering (SAXS) Study

We present the first report on the effects of hydrostatic pressure on colloidally stabilized lipid nanoparticles enveloping inverse nonlamellar self-assemblies in their interiors. These internal self-assemblies were systematically tuned into bicontinuous cubic (Pn3m and Im3m), micellar cubic (Fd3m), hexagonal (H2), and inverse micellar (L2) phases by regulating the lipid/oil ratio as the hydrostatic pressure was varied from atmospheric pressure to 1200 bar and back to atmospheric pressure. The effects of pressure on these lipid nanoparticles were compared with those on their equilibrium bulk, nondispersed counterparts, namely, inverse nonlamellar liquid-crystalline phases and micellar solutions under excess-water conditions, using the synchrotron small-angle X-ray scattering (SAXS) technique. In the applied pressure range, induced phase transitions were observed solely in fully hydrated bulk samples, whereas the internal self-assemblies of the corresponding lipid nanoparticles displayed only pressure-modulated single phases. Interestingly, both the lattice parameters and the linear pressure expansion coefficients were larger for the self-assemblies enveloped inside the lipid nanoparticles as compared to the bulk states. This behavior can, in part, be attributed to enhanced lipid layer undulations in the lipid particles in addition to induced swelling effects in the presence of the triblock copolymer F127. The bicontinuous cubic phases both in the bulk state and inside lipid cubosome nanoparticles swell on compression, even as both keep swelling further upon decompression at relatively high pressures before shrinking again at ambient pressures. The pressure dependence of the phases is also modulated by the concentration of the solubilized oil (tetradecane). These studies demonstrate the tolerance of lipid nanoparticles [cubosomes, hexosomes, micellar cubosomes, and emulsified microemulsions (EMEs)] for high pressures, confirming their robustness for various technological applications.

Synthesis of Hollow Platinum–Palladium Nanospheres with a Dendritic Shell as Efficient Electrocatalysts for Methanol Oxidation

Engineering the size, composition, and morphology of platinum-based nanomaterials can provide a great opportunity to improve the utilization efficiency of electrocatalysts and reinforce their electrochemical performances. Herein, three-dimensional platinum-palladium hollow nanospheres with a dendritic shell (PtPd-HNSs) are successfully fabricated through a facile and economic route, during which SiO2 microspheres act as the hard template for the globular cavity, whereas the triblock copolymer F127 contributes to the formation of the dendritic shell. In contrast with platinum hollow nanospheres (Pt-HNSs) and commercial platinum on carbon (Pt/C) catalyst, the novel architecture shows a remarkable activity and durability toward the methanol oxidation reaction (MOR) owing to the coupled merits of bimetallic nanodendrites and a hollow interior. As a proof of concept, this strategy is also extended to trimetallic gold-palladium-platinum hollow nanospheres (AuPdPt-HNSs), which paves the way towards the controlled synthesis of other bi- or multimetallic platinum-based hollow electrocatalysts.

Flexible Epoxy Resin Formed Upon Blending with a Triblock Copolymer through Reaction-Induced Microphase Separation.

In this study, we used diglycidyl ether bisphenol A (DGEBA) as a matrix, the ABA block copolymer poly(ethylene oxide–b–propylene oxide–b–ethylene oxide) (Pluronic F127) as an additive, and diphenyl diaminosulfone (DDS) as a curing agent to prepare flexible epoxy resins through reaction-induced microphase separation (RIMPS). Fourier transform infrared spectroscopy confirmed the existence of hydrogen bonding between the poly(ethylene oxide) segment of F127 and the OH groups of the DGEBA resin. Small-angle X-ray scattering, atomic force microscopy, and transmission electron microscopy all revealed evidence for the microphase separation of F127 within the epoxy resin. Glass transition temperature (Tg) phenomena and mechanical properties (modulus) were determined through differential scanning calorimetry and dynamic mechanical analysis, respectively, of samples at various blend compositions. The modulus data provided evidence for the formation of wormlike micelle structures, through a RIMPS mechanism, in the flexible epoxy resin upon blending with the F127 triblock copolymer.

Worm-hole structured mesoporous carbon monoliths synthesized with amphiphilic triblock copolymer

In the present work, mesoporous carbon monoliths with worm-hole structure had been synthesized through hydrothermal reaction by using amphiphilic triblock copolymer F127 and P123 as templates and resole as carbon precursor. Synthesis conditions, carbonization temperature and pore structure were studied by Fourier transform infrared, thermogravimetric analysis, transmission electron microscopy and N2 adsorption–desorption. The results indicated that the ideal pyrolysis temperature of the template is 450 °C. The organic ingredients were almost removed after further carbonized at 600 °C and the mesoporous carbon monoliths with worm-hole structure were obtained. The mesoporous carbon synthesized with P123 as single template exhibited larger pore size (6.6 nm), higher specific surface area (747 m2 g−1), lower pore ratio (45.9 %) in comparison with the mesoporous carbon synthesized with F127 as single template (with the corresponding value of 4.9 nm, 681 m2 g−1, 49.6 %, respectively), and also exhibited wider pore size distribution and lower structure regularity. Moreover, the higher mass ratio of template P123/resole induced similar pore size, larger specific surface area and lower pore ratio at the same synthesizing condition. It was also found that the textural structure of mesoporous carbon was affect by calcination atmosphere.

Co-templating Synthesis of Bimodal Mesoporous Silica for Potential Drug Carrier

Bimodal mesoporous silica is prepared by co-templating method using PEO-b-PLA diblock copolymer and F127 triblock copolymer. The pore size distribution of the mesoporous silica is bimodal, based on small angle X-ray scattering, transmission electron microscopy, and nitrogen adsorption-desorption isotherms analyses, and can be divided into the larger pores, originating from PEO-b-PLA, and the smaller pores, originating from F127. In addition, we are able to ascertain that the F127 triblock copolymer not only produces the smaller pores, but also acts as a swelling agent in the formation of the larger pores. This novel bimodal mesoporous silica is further successfully employed as a drug-carrier for doxorubicin in ambient conditions.

Controllable synthesis of mesoporous carbon nanospheres with uniform size by a facile one-pot aqueous strategy under highly acidic conditions

Because of the uncontrollable cross-linking rate of carbon precursors and the serious macroscopic phase separation during the organic–organic self-assembly process, the synthesis of mesoporous carbon nanospheres (MCNs) with uniform diameter<200 nm remains a challenge. In this study, we developed a direct acid-assisted, aqueous self-assembly method to synthesize such uniform MCNs with particle and pore sizes of ∼100 and ∼3.5 nm, respectively, by fine-tuning the volume ratio of ethanol/water under a high concentration of triblock copolymer F127 (7.9 × 10−4 mol L−1). The formation of uniform spheres was affected by the polymerization rate of carbon precursors and macroscopic phase separation, which are closely related to the amount of ethanol and F127. The highly acidic conditions could partially protonate carbon precursors and template, quickly inducing the self-assembly process with resorcinol/formaldehyde as carbon precursors and F127 as a morphology-controlling and interface-stabilizing agent. Because of their high surface area, large pore size, and nanoscaled and uniform spherical characteristics, the obtained MCNs loaded with the poorly water-soluble model drug itraconazole (ITZ) apparently increased the dissolution and release rates of ITZ.

Mesoporous Trimetallic PtPdRu Spheres as Superior Electrocatalysts.

Mesoporous Trimetallic PtPdRu Spheres with well-defined spherical morphology and uniformly sized pores were synthesized in an aqueous solution using ascorbic acid as the reducing agent and triblock copolymer F127 as the pore directing agent. These mesoporous PtPdRu spheres exhibited enhanced electrocatalytic activity compared to commercial Pt black, resulting in a ∼4.9 times improvement in mass activity for the methanol oxidation reaction. The excellent electrocatalytic activity and stability are due to the unique mesoporous architecture and electronic landscape between different elements.

Enhanced Binding of Phenosafranin to Triblock Copolymer F127 Induced by Sodium Dodecyl Sulfate: A Mixed Micellar System as an Efficient Drug Delivery Vehicle.

In this study, we explored the interaction of a cationic phenazinium dye, phenosafranin (PSF, here used as a model drug), with pluronic block copolymer F127, both in the presence and in the absence of the anionic surfactant sodium dodecyl sulfate (SDS), which forms mixed micelles with F127. We applied both steady-state and time-resolved spectroscopic techniques, along with isothermal titration calorimetry (ITC), to demonstrate the binding of the probe PSF to both the pluronic and F127/SDS mixed micelles. Dynamic light scattering (DLS) study revealed that, upon interaction with SDS, the hydrodynamic diameter (dH) of F127 micelles decreased due to the formation of the mixed micelles. The PSF penetrated to the more hydrophobic interior of the mixed micellar system as compared to F127 micelles alone. Micropolarity and fluorescence-quenching experiments revealed that PSF is more deeply seated in the case of F127/SDS mixed micelles. Through a partition coefficient, lifetime measurements, and time-resolved anisotropy experiments, we also established that the partitioning of the probe within the F127 micelles in the presence of SDS is almost double than that in its absence. ITC data corroborates the fact that the binding of PSF is the strongest and most thermodynamically favorable when mixed micelles are formed, which enables our system to serve as an excellent drug delivery vehicle when compared to F127 alone.

Synthesis of mesoporous sulfur-doped Ta2O5 nanocomposites and their photocatalytic activities

Mesoporous sulfur (S)-doped Ta2O5 nanocomposites have been synthesized for the first time through the sol-gel reaction of tantalum chloride and thiourea in the presence of a F127 triblock copolymer as structure directing agent. The as-formed mesophase S-doped Ta2O5 hybrid gels were calcined at 700°C for 4h to obtain mesoporous S-Ta2O5 nanocomposites. The experimental results indicated that the surface area of the S-doped Ta2O5 was up to 50m2g−1 and the pore diameter was controllable in the range of 3–7.7nm. The S-doped Ta2O5 nanocomposites behave as superior visible light-sensitive photocatalysts and the 1.5at.% S-doped Ta2O5 (S1.5) photocatalyst exhibited excellent photocatalytic activity of ∼92% for the photodegradation of methylene blue, identical to 80% TOC removal after three hours illumination under visible light. The photodegradation rate of S1.5 photocatalyst showed 3.4 times higher than the undoped Ta2O5 due to their narrow bandgap, large surface area, mesostructure and well crystalline state. The S1.5 photocatalyst could be recycled at least five times without an apparent decrease in its photocatalytic efficiency, indicating its high stability for practical applications. To the best of our knowledge, this is the first report that demonstrates one-step synthesis of mesoporous S-doped Ta2O5 nanocomposites as an efficient photocatalysts under visible light illumination.

Immobilization of Candida Antarctica lipase B on epoxy modified silica by sol-gel process

An epoxy-functionalized silica support was prepared through 3-glycidoxypropyltrimethoxylsilane(KH560)modified silica sol in the presence of triblock copolymer F127 (F-560-S). The surface chemistry, micromorphology and pore structure of the supports were characterized by TG, FTIR, SEM and N2 adsorption-desorption, which showed that the BET surface areas and pore volumes of epoxy-activated supports increased with the addition of F127. The Candida Antarctica Lipase B (CALB) was immobilized on the resulting carrier by covalent link. The lipase absorbed amounts were 58mg/g support and 375mg/g support on the normal silica (N-S) and modified silica (F-560-S), respectively. The immobilized lipases were examined as biocatalysts for transesterification of 1-phenethanol and vinyl acetate in nonaqueous medium. Solvents and temperature were investigated for influence of morphology and KH560 on the immobilized lipase. The catalytic activity of the CALB immobilized on F-560-S was improved in various solvents, especially in polar solvents. The immobilized CALBs maintained high activity, while the control experiment using free lipase gave very low ester production in the temperature range of 0–60°C. Furthermore improved thermal stability of CALB immobilized on F-560-S compared to the CALB on N-S was observed. The CALB immobilized on F-560-S exhibited high operational stability in organic media which still retained 88.3% of its original activity for 12h consecutive 7 runs.

Surfactant-Assisted Hydrothermal Synthesis of Cobalt Oxide/Nitrogen-Doped Graphene Framework for Enhanced Anodic Performance in Lithium Ion Batteries

In this work, the composites of nitrogen-doped graphene framework and Co3O4 nanoparticles with adjustable morphologies (NG/Co3O4) were fabricated via a surfactant-assisted hydrothermal route for first time. Three different surfactants including triblock copolymer F127, cetyltrimethyl ammonium bromide and sodium dodecyl sulfate are involved in the hybrid-assembly of graphene oxide, o-phthalonitrile and cobalt acetate in water/ethanol. Among the obtained samples, the one using F127 (NG/Co3O4-F127) manifests the most homogeneous distribution of Co3O4 NPs with the size of∼15nm in the macropore-walls formed by NG. As the anode material in lithium ion battery (LIB), NG/Co3O4-F127 exhibits excellent electrochemical performance, which is superior to the other composites and most of the previously reported Co3O4 based anode materials in LIBs.

Synthesis and characterization of calcium oxyboroapatite with bimodal porosity

Calcium oxyboroapatite with bimodal porosity and proposed general formula (CaO) x (PO2.5) y (BO1.5) z with 10 ≥ x ≥ 9, y ≥ 4 and z ≥ 1.6 have been prepared for the first time, by thermal processing of sol–gel-derived glass. F-127 triblock copolymer was incorporated in the sol–gel reactions as the structure directing agent under acidic conditions, whereas tributyl borate, triethyl phosphate and calcium nitrate were used as precursors for the glass structure. The prepared materials were chemically analyzed and characterized by X-ray diffraction (XRD), infrared absorption and Raman scattering spectroscopic techniques, where the related XRD patterns clearly revealed growth of rich in boron oxyboroapatite phase with increasing temperature. The oxyboroapatite phases treated at high temperatures exhibited bioactivity after soaking in simulated body fluid (SBF) solution within a few hours and these were observed by μ-Raman and scanning electron microscopy (SEM). Moreover, the external morphology of these materials has been directly observed with SEM microscopy before and after the immersion in SBF. Furthermore, mercury intrusion porosity measurements were taken in order to investigate the porosity, showing bimodal meso- and macro-porosity.

Synthesis of Xylylene-Bridged Periodic Mesoporous Organosilicas and Related Hollow Spherical Nanoparticles.

A variety of organosilicas with p-xylylene bridging groups in the framework were synthesized using Pluronic F127 triblock copolymer as a micellar template under moderately acidic conditions in the presence of xylene as a micelle swelling agent. The resulting materials were characterized by using nitrogen adsorption, small-angle X-ray scattering, transmission electron microscopy, and (29)Si and (13)C cross-polarization magic angle spinning NMR. As the ratio of the organosilica precursor to Pluronic F127 was decreased, the structure evolved from highly ordered periodic mesoporous organosilica (PMO) to weakly ordered PMO, loosely aggregated hollow organosilica nanospheres, and finally to a significantly aggregated disordered structure. The highly ordered PMO with primarily face-centered cubic structure was effectively a closed-pore material. However, the weakly ordered variant exhibited large-diameter (∼15 nm) spherical mesopores, which were accessible after calcination under appropriate conditions or after extraction. The hollow nanospheres had readily accessible, uniform inner cavities whose size was readily tunable by adjusting the amount of the swelling agent used. It was also possible to convert the organosilica nanospheres into hollow silica nanospheres with inaccessible (closed) mesopores. The formation of distinct well-defined morphologies with spherical mesopores for an organosilica with large bridging groups in the framework shows that block-copolymer-surfactant templating is a powerful and versatile method for controlling the nanoscale structures of these remarkable materials.

Amine-modified silica nanotubes and nanospheres: synthesis and CO2 sorption properties

Silica nanotubes (SNT) and silica nanospheres (SNS) were prepared in the presence of Pluronic F127 triblock copolymer.

A facile route to aqueous phase synthesis of mesoporous alumina with controllable structural properties

Mesoporous aluminas (MAs) with tunable structural properties, including BET surface area, pore volume and pore size, were successfully synthesized based on a sol–gel process via hydrolysis of aluminium isopropoxide associated with a structure-directing agent (SDA) as template in an acidic aqueous system. The effect of template type, template addition amount and inorganic aluminium precursor doping on the structural properties of the resulting MAs were systematically investigated. Four templates, including two non-ionic triblock copolymers P123 and F127, an amine based cationic quaternary surfactant cetyltrimethylammonium bromide (CTAB) and an anionic surfactant sodium dodecyl sulfate (SDS) were examined at varying amount. Three inorganic aluminium precursors, viz aluminium sulfate, aluminium nitrate and aluminium chloride, were used as the substitution aluminium sources to aluminium isopropoxide. The MAs synthesized were characterized using thermogravimetry – differential thermal analysis (TG–DTA) for decomposition and mass loss characteristics upon calcination, X-ray diffraction (XRD) for bulk crystallinity, transmission electron microscopy (TEM) for nano-scale morphology and N2 physisorption techniques for porous structural properties. For a given SDA, increasing the amount of surfactant addition markedly improved the porosity of the MA synthesized. In terms of the ability to influence the structural properties of the resulting MAs such as BET surface area, pore volume and pore size, the SDAs tested followed a descending order of F127 > P123 > CTAB > SDS. MAs with the greatest pore volumes and pore sizes with narrow PSDs were obtained when the doping ratios of Al(NO3)3, AlCl3 and Al2(SO4)3 were 15%, 30% and 2%, respectively. Depending on the type and addition amount of SDA and the aluminium precursor composition, the BET surface area, pore volume and pore size of MAs could be adjusted in the ranges of 178 m2 g−1 ∼ 358 m2 g−1, 0.4 cm3 g−1 ∼ 1.9 cm3 g−1 and 5.5 nm–30.1 nm, respectively.

The influence of poly(acrylic acid) on micellization and gelation characteristics of aqueous Pluronic F127 copolymer system

The influence of anionic homopolymer poly(acrylic acid) (PAA) of low (1800 g/mol) and high (450,000 g/mol) molecular weights on the micellization and gelation characteristics of aqueous Pluronic F127 (EO97PO69EO97) triblock copolymer (with EO = ethylene oxide and PO = propylene oxide) was studied using differential scanning calorimetry, dynamic light scattering, spectrophotometry, tube inversion technique, and rheometry. It is found that the addition of PAA decreases the critical micellization temperature (CMT) of F127 due to their association via hydrogen bonding. This association becomes stronger at temperatures ≥CMT, arising from the increased affinity between the PO units and PAA. F127-PAA complexation results in lesser PO dehydration and smaller micellization enthalpy (∆H). With increasing PAA concentration, this effect becomes stronger and more F127 bound on PAA is present in the sample, eventually leading to vanishing ΔH. In the presence of PAA, gel region of F127 decreases with increasing PAA concentration due to the order disrupting effect of PAA on the arrangement of packed micelles. Both the micellization and gelation processes of F127 in the presence of PAA are thermoreversible. The PAA effects on both processes become considerably weak at high pH.