The combination of small-angle X-ray scattering and qualitative porosimetry is applied to the puzzling phenomenon of overly large specific surface areas in some mesoporous silicas. Geometrical calculations, considering the relationship between structure, lattice parameter, and specific surface area, reveal the latter to be at least 1 order of magnitude smaller than experimental values obtained from sorption experiments, indicating the presence of micropores. Selective investigation of the mesopore system reveals that up to 63% of the specific surface area is due to microporosity. A relationship between the undirected creation of porosity and supramolecular templating is discussed.
Lyotropic phase morphologies of amphiphilic poly(butadiene-b-ethylene oxide) (PB-PEO) block copolymers are studied using transmission electron microscopy, small-angle X-ray scattering, smallangle neutron scattering, and polarized optical microscopy. The PB-PEO block copolymers form type-1 lyotropic phases comprising disordered micellar solutions (L1), spheres arranged on a bcc lattice (I1), hexagonally packed cylinders (H1), and lamellae (LR). Increasing molecular weight destabilizes the I1 and H1 phases and lowers the degree of order. For high molecular weight block copolymers the increase in chain conformational entropy leads to the formation of the sponge phase (L3). The transmission electron micrographs allow a detailed analysis of packing defects and epitaxial relations of the block copolymer lyotropic phases.
This study reports the lyotropic phase behavior of two poly(ethylene oxide)-b-poly(butadiene)
diblock copolymers and their cross-linking in the mesophase under retention of the mesoscopic order.
The lyotropic phase behavior in water was characterized by polarized light microscopy and small-angle
X-ray scattering (SAXS) in the concentration range from 0 to 100 wt % and in a temperature range between
20 and 100 °C. Depending on polymer composition and concentration micellar, hexagonal, lamellar, and
cubic phases are found. Their ranges as well as pronounced coexisting phase regions were determined.
Several of these mesophases were cross-linked via γ-irradiation to form mesostructured hydrogels. It is
shown that the cross-linked polymer gel essentially maintains the parental lyotropic order, as proven by
SAXS, polarized light microscopy, and transmission electron microscopy (TEM). TEM enables imaging
of the polymer gel structure and thereby the visualization of the liquid-crystalline mesophase morphologies
in themselves. The lyotropic mesophases as well as the lyotropic gels were used as templates for the
synthesis of mesoporous silica, which is expected to give a negative solid copy of the ordered soft matter
structure. The influence of the different templates on the silica structure formation is discussed.
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