Hydrogen bonding liquid crystalline benzoic acids with alkylthio groups: phase transition behavior and insights into the cybotactic nematic phase
| Autor: | Kazunobu Igawa, Yukito Sasaki, Hideto Tsuji, Yuki Arakawa |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Phase transition
Chemistry Stereochemistry Hydrogen bond Mesogen Electron donor 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Catalysis 0104 chemical sciences Crystallography chemistry.chemical_compound Liquid crystal Phase (matter) Materials Chemistry Alkoxy group Molecule 0210 nano-technology |
| Zdroj: | New Journal of Chemistry. 41:6514-6522 |
| ISSN: | 1369-9261 1144-0546 |
| DOI: | 10.1039/c7nj00282c |
| Popis: | A simple but novel class of hydrogen bonding liquid crystalline benzoic acids with alkylthio (or alkylsulfanyl; SR) groups was established. In general, although it is difficult for laterally non-substituted rod-like molecules with an alkylthio group to form some mesophases, the present molecules exclusively form a nematic (N) regime, owing to spontaneous carboxylic dimerization. It was found that the number of carbons in the alkylthio groups strongly correlated with transition temperatures as well as nematogenic stability: odd–even effects. Even-members displayed wider monotropic and enantiotropic N phases, despite the fact that almost all odd-members showed either none or only monotropic-narrower ones. Interestingly, their thermal transition temperatures were lower compared to those for alkoxy (OR) analogues, on account of the small angle (or large bend) of the C–S–C bond as well as the low electron density on their aromatic ring due to the weak electron donor properties of alkylthio groups. Additionally, in-depth wide-angle X-ray diffraction measurements revealed that an alkylthio analogue exhibited significantly enhanced smectic clusters formed in the N regime (or Ncyb phase) as well as the cluster type close to smectic (Sm) A, in comparison with an alkoxy analogue exhibiting a clear SmC-type cluster. The results indicate that a robust S⋯S intermolecular interaction for an alkylthio group into a mesogen affects the kind of smectic cluster in the Ncyb phase. |
| Databáze: | OpenAIRE |
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