A Structural Parameter to Link Molecular Geometry to Macroscopic Orientation in Discotic Liquid Crystals: Study of Metalloporphyrin Tapes

Novel liquid crystalline (LC) molecules were prepared from a triply linked dimeric porphyrin tape. A series of metal complexes (1Zn, 1Pd, 1Cu, and 1Ni) and the free-base form (12H) of...

Macroscopic ordering of helical pores for arraying guest molecules noncentrosymmetrically

Helical nanostructures have attracted continuous attention, not only as media for chiral recognition and synthesis, but also as motifs for studying intriguing physical phenomena that never occur in centrosymmetric systems. To improve the quality of signals from these phenomena, which is a key issue for their further exploration, the most straightforward is the macroscopic orientation of helices. Here as a versatile scaffold to rationally construct this hardly accessible structure, we report a polymer framework with helical pores that unidirectionally orient over a large area (∼10 cm2). The framework, prepared by crosslinking a supramolecular liquid crystal preorganized in a magnetic field, is chemically robust, functionalized with carboxyl groups and capable of incorporating various basic or cationic guest molecules. When a nonlinear optical chromophore is incorporated in the framework, the resultant complex displays a markedly efficient nonlinear optical output, owing to the coherence of signals ensured by the macroscopically oriented helical structure.

SAXS and in-situ SAXS to follow the structural evolution in hybrid materials

ABSTRACTThe paper focuses on the evolution of oriented nanostructures: An orientation in real space leads to scattering intensities with a preferred orientation with respect to the azimuthal angle in reciprocal space. Thus, the macroscopic orientation of nanostructures can be obtained from SAXS patterns. The additional advantage of in-situ SAXS is that one can directly follow the development of orientated nanostructures during thermal treatment, under extreme conditions or during processing. This is shown in the following for an orientational change of pores in two very different systems, the first being the formation of pores within carbon fibers during loading at high temperatures up to 2000 °C and the second is the development of macroscopically aligned pores in mesostructured silica in the sol-gel process during shear.

Methods to determine the pressure dependence of the molecular order parameter in (bio)macromolecular fibres

Combining FTIR spectroscopy and optical microscopy enables to correct the measured dichroism for the fibres' macroscopic orientation, and hence, separating pressure effects on macroscopic and microscopic scales.

Fabrication of Organized Nanofibrous Scaffolds to Mimic the Macroscopic Curvature of the Meniscus: Structure and Mechanics

The menisci are crescent-shaped fibrocartilaginous tissues which function to transmit and distribute loads between the femur and tibia of the knee joint. As such, the meniscus experiences complex loads, including tension, compression, and shear. Meniscus function in tension arises from an organized microstructure — bundles of highly aligned collagen circumnavigate the tissue between insertion sites on the tibial plateau (1). These aligned collagen bundles endow the tissue with mechanical properties that are highly anisotropic, and highest in the primary collagen orientation (2). Commercial products to replace the meniscus lack this unique structure and organization (3,4). To address engineering the knee meniscus, we have developed aligned nanofibrous scaffolds that can recapitulate this mechanical anisotropy (5,6). However promising, fibers within these scaffolds are unidirectional, while the fibers within the native tissue have a pronounced c-shaped macroscopic organization. To mimic this macroscopic orientation, we developed a new electrospinning method to collect organized fibers on a planar spinning disc (7). The objective of this study was to quantify the structure and mechanics of nanofibrous scaffolds collected using this novel technique and compare the data to aligned scaffolds obtained from a traditional electrospinning approach. We hypothesized that these circumferentially aligned (CircAl) scaffolds would behave similarly to linearly aligned (LinAl) scaffolds on short length scales, but exhibit marked differences in mechanics as the length scale increased.