Study of phase behavior in a system of linear hydrogen-bonded carboxylic acid homologues

Abstract

The system of hydrogen-bonded liquid crystals formed from binary mixtures p-nheptyloxybenzoic (I) acid and p-n-undecloxybenzoic (II) acid has been investigated by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction, and scattering and dielectric measurements. The TÀX phase diagram was obtained for this system. All mixtures show enantiotropic smectic and nematic phases. The crystalline phase represents a (a, b) solid solution. At the 2:1 ratio of I to II, an intermediate phase À co-crystal g À is formed. The co-crystal g possesses a much wider mesophase range than the corresponding initial components. In contrast to mixtures based on the solid solutions having a positive anisotropy, the co-crystal shows a negative dielectric anisotropy in the mesophase.

An FT-IR spectroscopic study of the role of hydrogen bonding in the formation of liquid crystallinity for mixtures containing bipyridines and 4-pentoxybenzoic acid

“…However, the presence of open dimers and catemer-like strands, see Fig. 8, stabilises the layered arrangements and hence, strongly promotes smectic phases, 67,68 see Fig. 14.…”

Cocrystals in Systems with Alkyloxybenzoic Acids: Formation Tendencies

“…Ранее были получены фазовые диаграммы, а также исследованы жидкокристаллические свойства бинарных систем, состоящих из гомологов ОБК с разным типом мезоморфизма: п-н-гептилоксибензойная -п-н-ундецилоксибензойная кислоты (7ОБК-11ОБК); п-н-гексилоксибензойная -п-ноктилоксибензойная кислоты (6ОБК-8ОБК) [23][24][25]. Установлено, что в системе 7ОБК-11ОБК при соотношении компонентов 2:1 образуется промежуточная фаза (сокристалл γ).…”