Studies of intermolecular proton transfer, its influence on the liquid crystal properties and electrically-driven transport of chiral ions in mixtures of chiral liquid crystalline 4-phenylpyridine derivative and organic acids of various strength

• Published in: Journal of molecular liquids Vol. 336; p. 116455
• Main Authors: Duda, Łukasz, Potaniec, Bartłomiej, Czajkowski, Maciej, Fiedot-Toboła, Marta, Palewicz, Marcin, Zdończyk, Maria, Madej, Anna, Cybińska, Joanna
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2021
• Subjects: Broadening of reflection band; Chiral ionic compounds; Electro-optical reflective modulator; Proton transfer; Electro-optical reflective modulator; Broadening of reflection band; Proton transfer; Chiral ionic compounds
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.116455

[Display omitted] •New fluorinated chiral liquid crystal 4-carboxybiphenyl acids have been synthesized.•Mid-IR analysis of intermolecular proton transfer in acid + phenylpyridine mixtures.•Formation of hydrogen-bonded associates or ionic salts depending on ΔpKa.•Solubility of some of ionic acid-base mixtures in nematic liquid crystal host noted.•Bistable and reversible switching processes and reflection band shift was found. Series of organic acids with various strength were mixed with chiral liquid crystalline 4-phenylpyridine derivative and tendency of these acid-base mixtures to form either intermolecular hydrogen-bonded associates or ionic systems was characterized basing on mid-infrared absorption spectroscopy. For this purpose several liquid crystalline 4-carboxybiphenyl acids were synthesized, including two new fluorinated chiral compounds, with enhanced strength of the acid. The stoichiometric acid-base mixtures were investigated in terms of their phase types and phase transition temperatures. The acid-base mixtures were doped into nematic liquid crystal host with negative dielectric anisotropy and characterized in terms of their miscibility in twisted nematic phase at room and elevated temperature and in terms of their helical twisting power. Selected mixtures exhibiting intermolecular proton transfer, good solubility in the liquid crystal host forming twisted nematic phase and sufficient helical twisting power to observe reflection band below 2500 nm were investigated in liquid crystal cells with respect to the change of the transmission in the near-infrared range upon high amplitude AC and DC electric fields, searching for broadening of the reflection band.