Triblock Copolymer Template Research Articles

Syntheses of NiO nanoporous films using nonionic triblock co-polymer templates and their application to photo-cathodes of p-type dye-sensitized solar cells

We prepared nanoporous NiO films from NiCl 2 in water/ethanol mixed solution, using a series of polyethyleneoxide–polypropyleneoxide–polyethyleneoxide (PEO–PPO–PEO) triblock co-polymers as template, and examined them as p-type NiO electrodes sensitized with a merocyanine dye. Triblock co-polymers with high PEO/PPO ratio leaded to three-fold higher photocurrent in comparison with low PEO/PPO polymers. Use of high PEO/PPO templates resulted in NiO membrane structure formed by uniformly distributed NiO nano particles with small interparticle voids, giving large surface area for dye adsorption, while low PEO/PPO templates resulted in larger void volume and less surface area. Photocurrent under simulated solar light was sum of the currents generated by NiO direct excitation and by dye-sensitization at spectra below 450 nm and from 450 to 590 nm, respectively.

Monodisperse Particles of Bifunctional Periodic Mesoporous Organosilica

Monodisperse particles of periodic mesoporous organosilica (PMO) with ethane- and phenylene-bridging groups were prepared using 1,2-bis(triethoxysilyl)ethane (BTEE) and 1,4-bis(triethoxysilyl)benzene (BTEB) organosilica precursors, and a Pluronic P123 poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) triblock copolymer template under slightly acidic conditions. Highly ordered monodisperse particles having hexagonal mesostructure (p6mm) and coiled shape were obtained only for the BTEE/BTEB molar ratios between 70:30 and 60:40. The average external diameter of these coiled particles was about 2−3 μm, whereas the diameter of mesopores present in these particles was about 7.4 nm.

Calcination and thermal degradation mechanisms of triblock copolymer template in SBA-15 materials

The calcination under air and degradation under inert atmosphere of as made SBA-15 surfactant templated mesostructured silica materials were studied using a combination of N 2 sorption at −196 °C, mass spectrometry (MS) monitored temperature programmed oxidation and degradation, thermogravimetric analysis (TGA), 13C MAS NMR and Fourier transform infrared (FTIR) spectroscopy. The characterization of the materials treated at different temperatures under oxidative and inert atmospheres indicated that both processes follow stepwise mechanisms. SBA-15 materials exhibit three families of pores: primary main mesopores, complementary intrawall mesopores (>2 nm) and intrawall micropores (<2 nm). Under oxidative atmosphere, the primary mesopores and the larger framework intrawall pores are first emptied below 200 °C with the production of volatile organic compounds (VOCs). This step is followed by an oxidation of the PEO chains from the intrawall micropores (<2 nm) producing CO 2 by combustion. Under inert atmosphere, the degradation of the organic template also begins first in the primary mesopores. However, an increase in the pore diameter up to 550 °C indicates that the complete liberation of primary mesopores is much slower than for calcination under air and occurs simultaneously with the removal of the PEO chains occluded within framework micropores.

Multifunctional periodic mesoporous organosilicas prepared with block copolymer: Composition effect on morphology

Bi- and trifunctional periodic mesoporous organosilica (PMO) materials were prepared using 1,4-bis(triethoxysilyl)benzene, 2,5-bis(triethoxysilyl)thiophene, and 1,2-bis(triethoxysilyl)ethane organosilica precursors, and a P123 PEO–PPO–PEO triblock copolymer template under a low acidic condition. PMO powders were observed to have an ordered hexagonal ( p6 mm) mesostructure with pore diameters in the range of 5.8–6.4 nm and displayed rod-(thiophene/ethane-rich PMOs) and rope-type (phenylene-rich PMOs) morphologies with different aspect ratios as the composition of organosilica precursors.

Synthesis and characterization of large-pore FDU-12 silica

Large-pore FDU-12 (LP-FDU-12) silicas with face-centered cubic structures of spherical mesopores of diameter 16–26 nm were synthesized using Pluronic F127 triblock copolymer template. The materials were characterized using small-angle X-ray scattering and nitrogen adsorption. The initial temperature range suitable for LP-FDU-12 synthesis was shown to be much wider than that reported earlier (7–15 °C vs. 14–15 °C). However, the degree of structural ordering was lower and the pore size distribution was broader in case of temperatures of 7–9 °C. The removal of the template by calcination resulted in a significant shrinkage (unit-cell parameter decrease by 10–16%) and afforded samples with low adsorption capacity, unless the synthesis involved a hydrothermal treatment in an HCl solution, which reduced the shrinkage and significantly increased the pore volume. The selection of time and temperature of the acid treatment allowed us to adjust the pore diameter of LP-FDU-12. However, the broadening of pore size distribution was observed for excessively long treatments at 130 °C. The treatment at 130 °C allowed us to tailor the pore entrance size in LP-FDU-12.

Multiple Functionalization of Mesoporous Silica in One‐Pot: Direct Synthesis of Aluminum‐Containing Plugged SBA‐15 from Aqueous Nitrate Solutions

AbstractAluminum‐containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X‐ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al‐containing plugged silicas possess well‐ordered hexagonal mesostructures with high surface areas (700–860 m2 g–1), large pore volume (0.77–1.05 cm3 g–1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma–atomic emission spectrometry results show that 0.7–3.0 wt % aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43–60% aluminum species are incorporated into the skeleton of the Al‐containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al‐containing plugged silica has a similar morphology to that of traditional SBA‐15. Furthermore, the Al‐containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities.

Preparation of 3D cubic ordered mesoporous bioactive glasses

3D body centered cubic ( I m 3 ¯ m ) and highly ordered mesoporous bioactive glasses (MBGs) were synthesized by evaporation-induced self-assembly (EISA) in the presence of a nonionic triblock copolymer template, EO 100PO 65EO 100 (F127). The influences of the concentration of F127, the reaction time, the heat-treated temperature, and the composition on the formation of the 3D cubic ordered MBGs were investigated. The 3D cubic MBGs have a large specific surface area (∼520 m 2 g −1) and pore volume (0.51 cm 3 g −1) with uniformly distributed pore size (5.4 nm). The formation of a long-range cubic mesostructure largely depends on the concentrations of F127 and CaO. The 3D cubic structure of the MBG shows relatively good thermal structural stability up to 800 °C because of the compositional homogeneity.

C60−PMO: Periodic Mesoporous Buckyballsilica

Here we report the first documented synthesis of a periodic mesoporous organosilica (PMO), that contains a multiply bonded C60 moiety integrated into the silica channel walls of the material, dubbed C60-PMO. This is accomplished through the acid-catalyzed co-assembly, of C60(NHCH2CH2CH2Si(OEt)3)x and tetraethylorthosilicate (TEOS) with a polyethyleneoxide-polylpropyleneoxide-polyethyleneoxide triblock copolymer template. The percentage of C60 in the final material was estimated to be a minimum of 63 vol %, but potentially as high as 91 vol %. The effects of the synthesis conditions on the mesostructure of the resulting materials are examined. In particular, we demonstrate that the C60 is uniformly distributed throughout the entire sample by the use of energy dispersive X-ray fluorescence (EDX) analysis and an OsO4 label bonded to the C60.

Periodic Mesoporous Organosilicas with Multiple Bridging Groups and Spherical Morphology

Bi- and trifunctional periodic mesoporous organosilicas (PMOs) with phenylene, thiophene, and ethane bridging groups were synthesized using 1,2-bis(triethoxysilyl)ethane (BTEE), 1,4-bis(triethoxysilyl)benzene (BTEB), and 2,5-bis(triethoxysilyl)thiophene (BTET) organosilica precursors and a poly(ethylene oxide)-poly(D,L-lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) triblock copolymer template under low acidic conditions. The PMO samples with different concentrations of organic bridging groups were obtained in the form of spherical particles having average diameters of 2-3 mum and 2D hexagonal (p6m) mesostructure with pore diameters of 7.3-8.4 nm. The particle morphology and chemistry of pore walls were tailored using different mixtures of organosilica precursors. Adsorption and structural properties of the aforementioned PMOs have been studied by nitrogen adsorption and small-angle X-ray scattering, whereas their framework chemistry was quantitatively analyzed by solid-state 13C and 29Si MAS NMR.

Disordered mesoporous silica low- k thin films prepared by vapor deposition into a triblock copolymer template film

Mesoporous silica films have been prepared by a vapor phase method using tetraethoxysilane (TEOS) in a batch reactor and in a continuous flow reactor. The TEOS molecules penetrated into a triblock copolymer films and then a triblock copolymer/silica composite structure was formed. A two dimensional grazing-incidence small angle X-ray scattering pattern and field emission scanning electron microscopy images of the films indicated that the films possess ordered and disordered regions. The tortuous pore channels in the wormhole-like disordered structure run parallel to the film surface. The mesostructured triblock copolymer/silica composite films were treated with a trimethylethoxysilane (TMES) vapor before and after calcination. The vapor infiltration treatments effectively improved mechanical strength and hydrothermal stability of the films. The dielectric constant of the TMES-treated mesoporous silica films was reduced into the 1.5–1.7 range.

Synthesis and morphological investigation of ordered SBA-15-type mesoporous silica with an amphiphilic triblock copolymer template under various conditions

Finely ordered SBA-15-type mesoporous silica materials were synthesized by templating with an amphiphilic block copolymer under various conditions, and their internal two-dimensional hexagonal mesostructures were confirmed by X-ray diffraction patterns, transmission electronic microscopy and nitrogen adsorption–desorption isotherms. Evaluation on morphological dependence of the synthetic conditions demonstrated that, for the samples synthesized through a one-step route, a variety of morphologies (e.g. short columns, spheres, hexagonal platelets, etc.) were achieved by means of adjusting acid species, reaction temperature, acidity and the concentration of inorganic salt. For the samples synthesized through a two-step route under mildly acidic conditions, the morphologies can be controlled by acidity of the solutions, and exhibits the irregularly faceted particles, the spherical ones, and the aggregated spheres by varying the pH from 1.02 to 2.61.

Preparation of mesoporous Co–B catalyst via self-assembled triblock copolymer templates

Mesoporous Co–B with worm-like morphology was firstly prepared via reduction of cobalt acetate by potassium borohydride in the presence of triblock copolymer templates. The as-prepared mesoporous Co–B was characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), and N 2 adsorption–desorption. During the hydrolysis of KBH 4, the mesoporous Co–B exhibited much higher catalytic activity than the regular Co–B. It is attributed to the larger specific surface area (163.77 m 2/g) and mesoporous channels. The average H 2 generation rate of the mesoporous Co–B was 3523 mL/min g catalyst in 1.3 wt% NaOH + 13 wt.% KBH 4 solution at 286 K, which may give a successive H 2 supply for a 571 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H 2 utilization. Furthermore, the as-prepared mesoporous Co–B with high specific surface area is expected to find applications in many catalytic hydrogenation reactions.

Preparation of Highly Ordered Mesoporous Thiophene–Silica with Spherical Macrostructure

Abstract Highly ordered mesoporous thiophene–silica powder was prepared using nonionic PEO–PLGA–PEO triblock copolymer templates and a 2,5-bis(triethoxysilyl)thiophene organosilica precursor under acidic conditions. The mesoporous thiophene–silica materials prepared with the EO16(L29G7)EO16 template were observed to have a well-defined spherical-like external morphology with a diameter of 2–5 μm, and a 2D hexagonal (p6mm) array of mesopores with a lattice constant of 9.55 nm. The thiophene–silica also displayed a large surface area of up to 1410 m2 g−1.

An Aqueous Cooperative Assembly Route To Synthesize Ordered Mesoporous Carbons with Controlled Structures and Morphology

A facile aqueous pathway has been demonstrated for the synthesis of ordered mesoporous carbon materials with hexagonal or cubic structures through the self-assembly of phenol/formaldehyde resols and triblock copolymer templates. Highly ordered mesoporous carbons FDU-16 with body-centered cubic structure (space group Im3m) have been synthesized under a basic aqueous condition by using triblock copolymer Pluronic F127 (EO106PO70EO106) as a template. Hydrocarbon (hexadecane or decane) can be used in the Pluronic P123 (EO20PO70EO20) system as a swelling agent to synthesize highly ordered mesoporous carbons FDU-15 with 2-D hexagonal (p6m) structure. The pore size of FDU-15 can be tailored from 4.1 to 6.8 nm by simply varying the hydrocarbon molecules. Mesoporous carbon materials FDU-14 with bicontinuous cubic (Ia3d) structure can be formed at a P123/phenol molar ratio higher than 0.04. A phase transformation from Ia3d to p6m occurs as the P123/phenol ratio decreases. It is proposed that the cooperative asse...

SELF-ASSEMBLY OF ORDERED SILVER NANOPARTICLE CHAINS ON TRIBLOCK COPOLYMER TEMPLATES

Poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer templates which present an in-plane cylinder pattern have been prepared by controlling the solvent evaporation rate. Then silver clusters have been deposited onto the SBS copolymer templates by low energy clusters beam deposition (LECBD) apparatus. The morphology of the sample has been characterized by AFM with tapping-mode. It is shown that silver clusters aggregate into nanoparticle chains onto the template at about 100% coverage. Optical absorption spectra reveal that the surface plasmon resonance (SPR) of silver nanoparticle chains occurs at 550 nm, being a red shift of -85 nm compared to silver nanoclusters deposited on the fused quartz substrate, and the width of SPR peak broadens.

Hierarchical Self-assembly of Silver Nanocluster Arrays on Triblock Copolymer Templates

Poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer templates which present in-plane cylinders of polystyrene (PS) aligned parallel to the plane of the substrate have been prepared by a solvent-induced order-disorder phase transition method. Silver nanoclusters have been obliquely deposited onto the SBS copolymer templates at low coverage, utilizing the directed low-energy cluster beam deposition (LECBD) method. The morphology of the samples has been characterized by a tapping-mode AFM. It is shown that the silver nanoclusters form ordered linear arrays and the intercluster distance within each individual linear array is comparable to the cluster size. Optical absorption spectra indicate that the surface plasmon resonance (SPR) of the silver nanocluster linear arrays occurs at about 444.5 nm, manifesting a red shift of approximately 21.4 nm compared to the SPR absorption of silver nanoclusters deposited on a fused quartz substrate. This is attributed mainly to the near-field electrodynamic interactions between the silver nanoclusters. This hierarchical approach to create ordered nanostructures transcends the spatial limits of lithography and provides a promising route to achieve well-ordered cluster-based nanostructures.

Preparation of Self-Standing, Submillimeter-Thick Porous Titania Films with Anatase Nanocrystallites Using Evaporation-Induced Self-Assembly

Self-standing transparent submillimeter-thick (∼0.34 mm) mesoporous titania films were prepared using the evaporation-induced self-assembly (EISA) of a triblock copolymer template and titanium tetraethoxide. Performing EISA at low temperature and low humidity improved the transparency and continuity of the films. As synthesized films had a well-defined hexagonal mesostructure and the existence of both amorphous titania and anatase nanocrystallites (2 nm) was confirmed. The films that were calcined at 400°C were composed of anatase nanocrystallites (14–16 nm) and had a BET surface area of 90 m2 g−1 with 13-nm pores. The films were characterized using XRD, FE-SEM, TEM, and N2 adsorption–desorption measurements.

Fabrication of conductive metallized nanostructures from self-assembled amphiphilic triblock copolymer templates: Nanospheres, nanowires, nanorings

Various metallized nanostructures (such as rings, wires with controllable lengths, spheres) have been successfully fabricated by coating metallic nanolayers onto soft nanotemplates through simple electroless methods. In particular, bimetallic nanostructures have been obtained by using simple methods. The multiple functional polymeric nanostructures were obtained through the self-assembly of polystyrene/poly(4-vinyl pyridine) triblock copolymer (P4VP- b-PS- b-P4VP) in selective media by changing the common solvent properties. By combining field emission scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization, it was confirmed that polymer/metal and bimetallic (Au@Ag) core–shell nanostructures could be achieved by chemical metal deposition method.

Periodic Mesoporous Organosilicas with Ethane and Large Isocyanurate Bridging Groups

Bifunctional periodic mesoporous organosilica was synthesized by co-condensation of tri[3-(trimethoxysilyl)propyl]isocyanurate and 1,2-bis(triethoxysilyl)ethane in the presence of a triblock copolymer template at low acid conentrations. This PMO features high surface area, large pore volume, and channel-like ordered mesopores, the walls of which contain two types of bridging groups, ethane and isocyanurate.

Luminescent europium complexes encapsulated in cage-like cubic ordered mesoporous silica

FDU-1 is a highly ordered, large-pore silica with a cage-like mesoporous cubic structure. FDU-1 was synthesized from tetraethyl orthosilicate (TEOS) in the presence of poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) triblock copolymer (PEO–PBO–PEO) template in strongly acid media, using a microwave oven as heating source. Rare earth complexes were encapsulated in ordered mesoporous silica in order to improve their thermal stability, necessary for applications. Eu(dbm) 3 · TPPO (dbm = dibenzoylmethane and TPPO = triphenylphosphine oxide) and Eu(pic) 3 · 2Leu · 5H 2O (pic = picrate and Leu = l-leucine) were encapsulated into FDU-1 silica and modified FDU-1 silica by 3-aminopropyltriethoxysilane (APTES). Thermogravimetry/derivative thermogravimetry (TG/DTG) showed that the decomposition temperature increased after encapsulation of the complex. Small angle X-ray diffraction (SAXRD) results showed that the mesoporous silica remains ordered after the encapsulation of the europium complexes. Rutherford back-scattering spectrometry (RBS) revealed a much higher Eu encapsulation for the dibenzoylmethane complex compared to picrate and, with a weight percent similar to the nominal concentration of Eu set at the synthesis process. All infrared spectra are similar and present the profile of amorphous silica. The complexes in FDU-1 silica still present luminescence.