| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1408036 | Journal of Molecular Structure | 2015 | 9 Pages |
•Equimolar mixtures of octyloxybenzoic acid/pyridine-based compounds show smectic behaviour.•Liquid crystalline behaviour linked to the shape of the hydrogen-bonded heterocomplex.•Carbonyl IR stretching region shows the presence of free acid, acid dimers and heterocomplexes.•1:1 hydrogen-bonded heterocomplex is not formed quantitatively.•Liquid crystalline behaviour must be accounted for in terms of competing equilibria.
The phase behaviour of equimolar mixtures of 4-octyloxybenzoic acid, OOBA, and either 1-(4-butylazobenzene-4′-oxy)-6-(4-oxypyridine)pentane, BuABO5OPyr, or 1-(4-butylazobenzene-4′-oxy)-6-(4-oxypyridine)hexane, BuABO6OPyr, is reported. OOBA exhibits enantiotropic smectic C and nematic phases, whereas BuABO5OPyr and BuABO6OPyr are not liquid crystalline. Both the OOBA/BuABO5OPyr and OOBA/BuABO6OPyr equimolar mixtures show an enantiotropic smectic A phase identified using X-ray diffraction and polarised light microscopy. The liquid crystallinty of the mixtures is attributed, in part, to the formation of a 1:1 hydrogen-bonded complex between OOBA and either BuABO5OPyr or BuABO6OPyr. Differences in the transitional properties of the mixtures are accounted for in terms of the average shapes of these 1:1 complexes. Temperature dependent FTIR spectroscopy shows, however, that the formation of the complex is not quantitative in the mixtures but instead a complex mixture exists over the complete temperature range studied, involving the 1:1 complex, both cyclic and open acid dimers, free acid and hence, free BuABOnOPyr molecules.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide
