Synthesis and Self-Assembly of Donor−Spacer−Acceptor Molecules. Liquid Crystals Formed by Single-Component “Complexes” via Intermolecular Hydrogen-Bonding Interaction

Abstract

A series of donor-spacer-acceptor molecules, 4-{[n-(4-stilbazoyl)]alkyloxy}benzoic acid, where n is the number of carbon atoms in alkyloxy chain and equals to 6, 8, 10, and 12, respectively, for 6a-d, were synthesized. The molecular "complexes" formed by identical 6a-d molecules generated hydrogen-bonded liquid-crystalline polymers by connecting a rigid donor and a rigid acceptor of the molecules via hydrogen-bonding interaction. The thermal behaviors were studied by differential scanning calorimetry, polarizing microscopy and X-ray diffraction. The phase transition temperature of 6a-d on both cooling and heating decreased steadily with the increase in length of the spacer. The hydrogenbonding interaction in 6a-d was investigated by X-ray photoelectron spectroscopy and FT-IR spectroscopy. The intermolecular hydrogen-bonding interaction was evidenced by the fact that there were two characteristic bands at 2450 and 1920 cm -1 in the FT-IR spectra and the change in binding energy of N 1s by 0.72-0.88 eV relative to its reference compound trans-4-octyloxy-4′-stilbazole (7) were observed.

Self-assembly and supramolecular liquid crystals based on organic cation encapsulated polyoxometalate hybrid reverse micelles and pyridine derivatives

“…The detailed assignments of other absorption bands are summarized in SI. For SEP-Si/PY3, we can also see the characteristic vibration bands appearing at about 1923 and 2474 cm À1 deriving from OH stretching, and at 1697 cm À1 deriving from carbonyl stretching, confirming that the hydrogen-bonding occurs between carboxylic acid and pyridine [32][33][34]. Other bands are apparently from the characteristic vibrations of reverse micelle and pyridine.…”

“…1730 cm À1 . And two halo bands that represent intermolecular hydrogen bond emerge at 1922 and 2483 cm À1 , obviously confirming that the hydrogen-bonding between benzoic acid and pyridine derivatives still exists in the high temperature region, where LC states locate at [32][33][34][35][36][37][38][39][40][41]. In addition to the well maintained hydrogen-bonding, the vibrations of CH 2 antisymmetric and symmetric stretching move to the higher wavenumber somewhat, implying the alkyl chains of the assembly in disordered state.…”

“…S3B). This texture is a common characteristic of smectic B phase, particularly when it is obtained through directly decreasing temperature from isotropic liquid [33][34][35].…”

“…Apparently, the increase in layer distance should be derived from both the increase in molecular length of PY3 in comparison with PY2 and the order packing of the alkyl chain. The appearance of a single sharp diffraction in wide-angle region indicates the SmB phase [33][34][35]. For SEP-Si/PY5, it features a smectic phase with a periodicity of 2.9 nm during its cooling run from isotropic state, as demonstrated by the presence of equidistant diffractions in the small-angle region (Fig.…”

Self-assembly of azobenzene based side-chain liquid crystalline polymer and n-alkyloxybenzoic acids

“…If polymer containing a pendant group capable of forming hydrogen bonding * For correspondence could be used to stabilize and enhance mesomorphic property and these interactions are much stronger than dipole-dipole interaction. [17][18][19] This type of interaction possesses utility in the area of miscibility of liquid crystalline blends and in design of novel guest-host liquid crystalline systems as well. Photoisomerization of azobenzene has been used to design photochromic liquid crystals, as rod-like trans-isomer of azobenzene is known to stabilize LC phase, whereas bent shaped cis-isomer destabilizes this LC phase.…”