Lyotropic Phase Morphologies of Amphiphilic Block Copolymers

Förster, Stephan; Berton, Beate; Hentze, Hans‐Peter; Krämer, Eckart; Antonietti, Markus; Lindner, Peter

doi:10.1021/ma001923h

Cited by 102 publications

(113 citation statements)

References 71 publications

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“…Previous studies of cylindrical block copolymer micelles do report the existence of a hexagonal phase occurring at high concentrations, [24][25][26][27][28] however in all cases where the order is discussed, this appears to be a regular, translationally well-ordered phase. Another possible phase for systems of concentrated semi-flexible rods is the hexatic, which exhibits long-range sixfold orientational order but only short range translational order.…”

Section: Introductionmentioning

confidence: 83%

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

et al. 2016

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This paper presents a detailed analysis of the structure of the hexagonal phase of poly(ferrocenylsilane) (PFS)-based cylindrical micelles found at concentrations above ca. 5 wt. % in non-polar solvents such as decane. Small angle X-ray scattering indicated that the hexagonal order is not long-range. In all samples, deviations in the lower order peak positions were observed with respect to those expected for a perfect hexagonal lattice, with the degree of deviation correlating with the micelle length. Furthermore, analysis of the peak shapes and peak widths suggest that the phase possesses intermediate translational order similar to the hexatic phase. The observed features can be reproduced by amending Hosemann's paracrystal theory to include a distribution of lattice parameters to model well and poorly condensed regions. It is proposed that this distribution arises due to the bending and intertwining of individual micelles in a hexagonal lattice resulting in a kinetically-trapped phase that is initially neither perfectly hexagonal nor canonically hexatic but which anneals over time towards a perfect hexagonal lattice.

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Section: Introductionmentioning

confidence: 83%

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

et al. 2016

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“…The PB-PEO block copolymers were synthesized by a new approach developed by Förster et al [10]. Sol-gel synthesis of silica in the presence of ABC templates was carried out as described previously [5].…”

Section: Methodsmentioning

confidence: 99%

Nanoporous Silicas by Casting the Aggregates of Amphiphilic Block Copolymers: The Transition from Cylinders to Lamellae and Vesicles

et al. 1999

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The synthesis of mesoporous ceramic oxides with pore sizes between 2 and 50 nm is a recent trend in materials science. Most mesoporous silicas are prepared using ionic low molecular weight surfactants as structure-directing agents and sometimes inert oils as swelling additives.[1] This process, involving the precipitation of a surfactant-rich gel phase, is restricted to the synthesis of materials with pore sizes smaller than 8 nm, as the silica walls are too thin to support a larger-pore network. The use of bulk lyotropic liquid crystal phases of low molecular weight non-ionic surfactants [2±4] as templates partially solves the problem of mechanical stability. The wall thickness depends on the amount of inorganic precursor present in the preparation mixture, because the nanostructure is a result of directly casting the lyotropic bulk phase. However, surfactants are only available with restricted lengths of the hydrophobic chain, so that again the pore diameter is limited to approximately 4.5 nm.Casting the lyotropic phases of amphiphilic block copolymers (ABCs) is the method of choice for the synthesis of mechanically stable large-pore systems.[5] Here, the solidification of a siliceous precursor takes place in the aqueous domains of the microphase-separated medium, hence producing a monolithic cast of the original supramolecular aggregate. In addition, the ABC liquid crystal approach affords coherent porous coatings and macroscopic objects with continuous pore systems. [6] This approach was subsequently adopted by Chmelka et al., [7] who employed commercially available Pluronic-type triblock copolymers and obtained materials with pore diameters between 4.7 and 30 nm, and wall thicknesses between 3 and 5 nm. Their observations confirm the superiority of polymeric templates as porogens. [6] In this contribution, we present new non-ionic polymer templates with improved water-solubilities and a broader range of accessible molecular weights, which allows pore diameters of ceramic nanostructures to be extended beyond the known limits of this casting procedure. Templating the lyotropic aggregate structure of poly(butadiene-bethylene oxide) (PB-PEO) was studied over a wide range of block lengths, block length ratios and polymer concentration. The resulting silicas were characterized by transmission electron microscopy (TEM), porosimetry, and small-angle X-ray scattering (SAXS). The results demonstrate the great potential inherent in ABC templating as the method of choice for pore design in ceramic oxides. The polymers used in the experiments and their analytical data are summarized in Table 1. Table 1. Physical data of the amphiphilic block copolymers.[a] GPC measurement using CHCl 3 for the precursor PB (PB standard), the PEO block length is calculated from 1 H-NMR spectra (M n = number average molecular weight´10 3 kg/mol).[b] Repeat units.[c] Polydispersity, GPC in CHCl 3 , RI.The lyotropic phase behavior of the amphiphilic block copolymers in water was studied by polarized-light optical microscopy, as SAXS experime...

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“…[62][63][64] Fig. 8 depicts two unconventional phases and their nanocasting replicas, the bicontinuous sponge-like phase (Fig.…”

Section: Amphiphilic Block Copolymers As Templatesmentioning

confidence: 99%

Porous materials via nanocasting procedures: innovative materials and learning about soft-matter organization

2002

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Nanocasting, the 3D-transformation of self-assembled organic nanostructures into hollow inorganic replicas under preservation of fine structural details has recently turned out to be a versatile tool, both for the synthesis of porous media with new pore topology as well as for the characterization of the assembled structures themselves. This review gives a review on recent work describing the potential and restrictions of nanocasting using surfactants, polymers, colloids as well as supramolecular tectons as porogens.

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Lyotropic Phase Morphologies of Amphiphilic Block Copolymers

Cited by 102 publications

References 71 publications

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

Nanoporous Silicas by Casting the Aggregates of Amphiphilic Block Copolymers: The Transition from Cylinders to Lamellae and Vesicles

Porous materials via nanocasting procedures: innovative materials and learning about soft-matter organization

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