Vertical Columnar Block-Copolymer-Templated Mesoporous Silica via Confined Phase Transformation

Platschek, Barbara; Petkov, Nikolay; Himsl, Dieter; Zimdars, Silvia; Li, Zhuo; Köhn, Ralf; Bein, Thomas

doi:10.1021/ja803102y

Cited by 45 publications

(79 citation statements)

References 33 publications

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“…Lithium chloride was chosen as the inorganic additive because of its significant effect on the micellar hydration and gelation behavior of PEO-PPO-PEO triblock copolymers in solution. 55,56 The added LiCl indeed had a striking impact on the phase behavior, as the resulting PMO/AAM composites now showed a mesophase with the cubic Im 3m structure (body centered cubic), which is different from the original 2D hexagonal circular mesophase obtained without salt addition. The 2D-SAXS pattern of F127-cubic-200 Bp-PMO (F127-cubic sample calcined at 200 C) shows the typical reflections assigned to the cubic Im 3m phase (Fig.…”

Section: F127-cubic Bp-pmomentioning

confidence: 92%

“…43 Another reason for the absence of shrinkage might be the added inorganic ions, which have been observed to increase the chemical interactions between organic silica mesophases and the AAM channel surface. 55 The nitrogen sorption isotherm (Fig. 6) of F127-cubic-250 Bp-PMO (F127-cubic sample calcined at 250 C) shows the type IV shape with a broad hysteresis loop that is attributed to the existence of bottlenecks connecting pores in the cubic system.…”

Section: F127-cubic Bp-pmomentioning

confidence: 99%

“…The presence of Li + ions and Cl À ions can change the micellar hydration behavior of the pluronic F127 solution and thus change the curvature of the micelles. 55,56,58,59 Specifically, on the one hand, the Cl À ion has the effect of dehydrating hydrophilic groups of F127 micelles and thus decreasing the curvature of F127 micelles. On the other hand, hydrated Li + ions can form complexes with the PEO chains in the micellar corona region, [58][59][60] which can enlarge the hydrophilic head groups of the F127 micelles.…”

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Hierarchically structured biphenylene-bridged periodic mesoporous organosilica

Keilbach

Kienle

et al. 2011

J. Mater. Chem.

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Novel composites of highly ordered and stable biphenyl-bridged periodic mesoporous organosilica (PMO) materials confined within the pores of anodic alumina membranes (AAM) were successfully synthesized by evaporation-induced self-assembly (EISA). 4,4 0 -Bis(triethoxysilyl)biphenyl (BTEBP) was used as a precursor in combination with the ionic surfactant cetyltrimethylammonium bromide (CTAB) or triblock-copolymer F127 as structure-directing agents. The resulting mesophases were characterized by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM).With ionic CTAB as a structure directing agent, samples with a mixture of the 2D-hexagonal columnar and a lamellar mesophase were obtained within the AAM channels. When using the nonionic surfactant F127, mesophases with a 2D-hexagonal circular structure were formed in the AAM channels. Additionally, a cubic Im 3m phase could also be obtained with the same nonionic surfactant after the addition of lithium chloride to the precursor solution. The stability of both the circular and cubic biphenylene-bridged PMO against calcination temperatures of up to 250 C was confirmed by NMR spectroscopy. Nitrogen sorption in the porous composite membrane shows typical type IV isotherms and narrow pore size distributions. All the biphenyl PMO/AAM composites show fluorescence due to the existence of biphenyl chromophores in the stable organosilica framework.

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Section: F127-cubic Bp-pmomentioning

confidence: 92%

Section: F127-cubic Bp-pmomentioning

confidence: 99%

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confidence: 99%

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Hierarchically structured biphenylene-bridged periodic mesoporous organosilica

Keilbach

Kienle

et al. 2011

J. Mater. Chem.

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“…Recently we and others have shown that mesoporous silica channels can be successfully aligned using highly oriented nature of the PAAs membranes [89] shown in figure 8. Samples with a columnar hexagonal 2D structure along the vertical channels of the AAM can be produced with ionic CTAB as template.…”

Section: Vertical Orientationmentioning

confidence: 99%

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Farrell

Petkov²,

Morris

et al. 2010

Journal of Colloid and Interface Science

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Self-assembled nanoscale porous architectures, such as mesoporous silica films (MPS), block copolymer films (BCP) and porous anodic aluminas (PAAs), are ideal hosts for templating one dimension (1 D) nano-entities for a wide range of electronic, photonic, magnetic and environmental applications. All three templates offer dimensional scalability and tunability over a wide range, with critical pore sizes for each system well below the 20 nm threshold [1][2][3]. Recently, research has progressed towards controlling the pore direction, orientation and long range order of these nanostructures through so called directed self-assembly (DSA). Significantly, the introduction of a wide range of top-down chemically and physically pre-patterning substrates has facilitated the DSA of nanostructures into functional device arrays. The following review begins with an overview of the fundamental aspects of self-assembly and ordering processes during the formation of PAAs, BCPs and MPS films. Special attention is given to the different ways of directing self-assembly, concentrating on properties such as uni-directional alignment, precision placement and registry of the self-assembled structures to hierarchal or top down architectures. Finally, to distinguish this review from other articles we focus on research where nanostructures have been utilised in part to fabricate arrays of functioning devices below the sub 50 nm threshold, by subtractive transfer and additive methods. Where possible, we attempt to compare and contrast the different templating approaches and highlight the strengths and/or limitations that will be important for their potential integration into downstream processes. ACCEPTED MANUSCRIPT 3 SECTION 1.0: SELF ASSEMBLY AND NANO-ARCHITETCURESThe diversity of self-assembled nanostructures and more importantly, their precise orientation within a thin film (fixed to a substrate) ultimately determines their function and overall application. A large population of research reports to date have focused on identifying these orientations and related periodicities, using x-ray and microscopy tools, as well the development of methods for readily manipulating nanostructures, such as pre-patterning of silicon substrates for the alignment of block copolymers (BCPs) [4] and mesoporous thin films (MTFs) [5] and altering the growth direction of porous anodic alumina (PAA) templates [6]. In this section, a brief synopsis of the mechanisms behind the self-assembly/organisation of each system and highlight nanoscale architectures (and orientations), which are important from a device perspective. Templated mesoporous thin filmsOrdered mesoporous powders were first discovered by researchers at the Mobil Petrochemical Corporation in 1992 and shortly after, sol-gel derived mesoporous silica films were fabricated [1,7].The first series of ordered mesoporous films were reported by Yang et al. in 1996 [8], prepared using initial surfactant concentrations above their critical micelle concentration (CMC). However the films prepared fil...

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“…The authors also found a strongly favorable effect of the addition of inorganic salts on the phase-formation process in combination with reduced shrinkage. [19] The kinetics of the mesostructure formation and phase transformations between the two hexagonal phases were investigated by in situ grazing-incidence smallangle X-ray scattering (GISAXS) measurements. [20] Further progress on the way to confined mesoporous organic phases was accomplished by Keilbach et al [21] by synthesizing periodic mesoporous organosilicas (PMOs) in AAM pores.…”

Section: Introductionmentioning

confidence: 99%

Cubic and Hexagonal Mesoporous Carbon in the Pores of Anodic Alumina Membranes

Schuster¹,

Keilbach²,

Köhn³

et al. 2011

Chemistry A European J

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Cubic and circular hexagonal mesoporous carbon phases in the confined environment of the pores of anodic alumina membranes (AAM) were obtained by organic-organic self-assembly of a preformed oligomeric resol precursor and the triblock copolymer templates Pluronic F127 or P123, respectively. Casting and solvent evaporation were followed by self-assembly and the formation of a condensed wall material by thermopolymerization of the precursor oligomers, thus resulting in mesostructured phenolic resin phases. Subsequent thermal decomposition of the surfactant and carbonization were achieved through thermal treatment at temperatures up to 1000 °C under an inert atmosphere. The resulting hierarchical mesoporous composite materials were characterized by small-angle X-ray scattering and nitrogen-sorption measurements. The structural features were directly imaged in TEM cross-sections of the composite membranes. For both structures, the AAM pores were completely filled and no shrinkage was observed due to strong adhesion of the carbon-wall material to the AAM pore walls. As a consequence, the pore size of the mesophase system stays almost constant even after thermal treatment at 1000 °C.

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Vertical Columnar Block-Copolymer-Templated Mesoporous Silica via Confined Phase Transformation

Cited by 45 publications

References 33 publications

Hierarchically structured biphenylene-bridged periodic mesoporous organosilica

Hierarchically structured biphenylene-bridged periodic mesoporous organosilica

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Cubic and Hexagonal Mesoporous Carbon in the Pores of Anodic Alumina Membranes

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