Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.

Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

Structures and properties of liquid crystalline phases formed by bent-core molecules are reviewed. At least eight phases designated as B1–B8 have been found, being unambiguously distinguished from phases formed by usual calamitic molecules due to a number of remarkable peculiarities. In addition to B1–B8 phases, smectic A-like phases and biaxial nematic phases formed by bent-core molecules are also reviewed. The most attractive aspects of this new class of liquid crystals are in polarity and chirality, despite being formed from achiral molecules. The bent-core mesogens are the first ferroelectric and antiferroelectric liquid crystals realized without introducing chirality. Spontaneous chiral deracemization at microscopic and macroscopic levels occurs and is controllable. Moreover, achiral bent-core molecules enhance system chirality. The interplay between polarity and chirality provides chiral nonlinear optic effects. Further interesting phenomena related to polarity and chirality are also reviewed.

https://iopscience.iop.org/article/10.1143/JJAP.45.597/pdf

Bent-Core Liquid Crystals: Their Mysterious and Attractive World

An overview is given of theory and experiments on liquid crystal phases which appear in solutions of elongated colloidal particles or stiff polymers. The Onsager (1949) virial thecry for the isotropionematic transition of thin rodlike particles is treated comprehensively along with extensions to polydisperse solutions and soft interactions. Computer simulations of liquid crystal phases in hard particle fluids are summarized and used to assess the quality of statistical mechanical thwries for stiff panicles at higher dume haion-like the inclusion of higher Virial coefficients, yexpansion, scaled particle theory and density functional theory. Both computer simulations and density functional theory indicate formation of more highly ordered smectic phases. The range of experimental applicability h strongly widened by the extension of the viriai theory to wormlike chains by Khokhlov and Semenov (1981, 1982). Fmally, experimental results for a number of carefully studied, charged and uncharged colloids and polymers are summarized and wmpared to theoretical results. IE many cases the agreement is semi-quantitative.

/pdf/phase-transitions-in-lyotropic-colloidal-and-polymer-liquid-23qsyytblc.pdf

Phase transitions in lyotropic colloidal and polymer liquid crystals

Discotic Liquid Crystals.

The blue phases of cholesteric liquid crystals are liquids that exhibit orientational order characterized by crystallographic space-group symmetries. We present here a pedagogical introduction to the current understanding of the equilibrium structure of these phases accompanied by a general overview of major experimental results. Using the Ginzburg-Landau free energy appropriate to the system, we first discuss in detail the character and stability of the usual helical phase of cholesterics, showing that for certain parameter ranges the helical phase is unstable to the appearance of one or more blue phases. The two principal models for the blue phases are two limiting cases of the Ginzburg-Landau theory. We explore each limit and conclude with some general considerations of defects in both models and an exact minimization of the free energy in a curved three-dimensional space.

Crystalline liquids: the blue phases

The phase diagram of the ternary system potassium laurate-1-decanol-D$_{2}\mathrm{O}$ was studied over concentration ranges where nematic phases are likely to occur. Two uniaxial nematic phases which are separated by a biaxial nematic phase are found. In limited concentration range the following phase sequence may be observed reversibly on heating and on cooling: isotropic-uniaxial nematic (positive optical anisotropy)-biaxial nematic-uniaxial nematic (negative optical anisotropy)-biaxial nematic-uniaxial nematic (positive optical anisotropy)-isotropic.

Observation of a Biaxial Nematic Phase in Potassium Laurate-1-Decanol-Water Mixtures

Abstract Acute respiratory distress syndrome is the most severe form of acute lung injury (ALI) and is associated with significant mortality. Lipopolysaccharide (LPS)-induced injury is a valuable murine model of ALI but there is a paucity of data on lung regeneration and the role of angiogenic signaling involving vascular endothelial growth factor (VEGF). Eight-week-old male C57BL/6J mice were randomized to receive intratracheal instillation of either LPS or isovolumetric phosphate buffered saline as a vehicle control. Mice were observed at a single follow-up time-point that was either short-term (24 h or 4 days) or long-term (7 days or 4 weeks). On pulmonary function testing, LPS-treated mice had increased compliance at 4 weeks post-instillation, which correlated with decreased vascularization and with time-dependent, progressive decrease in alveolarization. Treadmill exercise tolerance testing demonstrated impaired performance at 24 h, 4 days and 4 weeks following LPS exposure. On lung protein analysis, LPS instillation decreased VEGF expression at up to 4 weeks, and decreased activation of its key receptor, VEGFR2 at 7 days and 4 weeks post-instillation. Together, these data provide insight on long-term pulmonary functional outcomes 4 weeks after ALI and identify angiogenic proteins as possible therapeutic targets following lung injury. 

/pdf/lipopolysaccharide-induced-murine-lung-injury-results-in-3f2a9g22.pdf

L. J. Yu

Papers

Observation of a Biaxial Nematic Phase in Potassium Laurate-1-Decanol-Water Mixtures

Lipopolysaccharide-induced murine lung injury results in long-term pulmonary changes and downregulation of angiogenic pathways

An in-line digestive cartridge increases enteral fat and vitamin absorption in a porcine model of short bowel syndrome.