Search

Liquid crystal (LC) dimers with well‐defined composition and structure arouse broad attentions for their exhibiting LC properties beyond conventional low molar mass mesogens and serving as fascinating model compounds for LC polymers. Here in this work, a series of LC dimers bridged with a phosphonic group have been synthesized through a facile free radical mediated addition reaction between hypophosphorous acid and vinyl terminated cyanobiphenyl mesogens with variant length alkyl spacers. In addition, two esterified derivatives and a group of mono‐addition homologues with a terminal phosphonic acid group have also been prepared for comparison study. All the newly synthesized compounds exhibit monotropic nematic (N) phase with typical schlieren textures except for the LC dimer with the longest eleven‐methylene spacer, which surprisingly shows twist‐bend nematic (NTB) phase directly from the isotropic state upon cooling. Moreover, the thermal transition properties such as the nematic‐isotropic transition temperatures and associated entropy changes of the series LC dimers display a modest odd‐even effect. Furthermore, both the LC dimers and the mono‐addition homologues in N phase are quite easy to achieve homeotropic alignment upon annealing thanks to the supramolecular interactions between the introduced phosphonic acid group and the hydroxylated glass surface. This work thus provides a novel synthesis strategy for a class of LC materials bridged with a phosphonic acid group prone to further functionalization, which may serve as promising vertical alignment agents and pave the way for developing a new kind of functionalized LC materials of NTB phase. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we designed a kind of aggregation‐induced emission (AIE) chiral fluorescence emitters (R/S‐BINOL‐CN enantiomers) in the aggregate state. Chiral emissive nematic liquid crystals (N*‐LCs) prepared by doping this kind of AIE‐active R/S‐BINOL‐CN enantiomers into a common achiral nematic liquid crystal (N‐LC, E7) can self‐assemble as the regularly planar Grandjean texture leading to high luminescence dissymmetry factor (glum) of aggregation‐induced circularly polarized luminescence (AI‐CPL) signal up to 0.41, which can be attributed to dipolar interactions from polar cyano groups and π–π interactions between binaphthyl moiety of the dopant R/S‐BINOL‐CN and biphenyl group of the host molecules (E7). [ABSTRACT FROM AUTHOR]

A series of meta-substituted fatty acid octaester derivatives and their transition-metal complexes of meso- tetraphenyl porphyrins (TPP-8OOCR, with R=C n−1H2 n−1, n=8, 12, or 16) have been prepared through very simple synthesis protocols. The thermotropic phase behavior and the liquid crystalline (LC) organization structures of the synthesized porphyrin derivatives were systematically investigated by a combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM), and variable-temperature small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS) techniques. The shorter octanoic acid ester substituted porphyrin (C8-TPP) did not show liquid crystallinity and its metal porphyrins exhibited an uncommon columnar mesophase. The lauric acid octaester (C12-TPP) and the palmitic acid octaester (C16-TPP) series porphyrins generated hexagonal columnar mesophase Colh. Moreover, the metal porphyrins C12-TPPM and C16-TPPM with M=Zn, Cu, or Ni, exhibited well-organized Colh mesophases of broad LC temperature ranges increasing in the order of TPPNi