Phase transition behavior of pentylcyanobiphenyl liquid crystal containing n-dodecyl-2-hydroxy-1-naphthaldimine

Abstract

The present work focuses on the phase transition behavior of a thermotropic liquid crystal incorporating a Schiff base having a terminal alkyl chain of 12 carbons, such as, n-dodecyl-2-hydroxy-1-naphthaldimine (SB). Given its interesting molecular structure, the SB was chosen as doping agent for a liquid crystal of cyano-biphenyl type, such as, 4-cyano-4′-n-pentyl-biphenyl (5CB). The study of the guest–host systems, at different concentrations of the solute, was performed using differential scanning calorimetry and UV–visible spectroscopy, equipped with the hot compartment. The fusion and the nematic – isotropic transition temperatures as well as the enthalpies ΔH⁰ and entropies ΔS⁰ variations of the 5CB-based systems were determined from their spectral data. The thermal properties and orientational order parameters were also determined for the pure and SB doped 5CB, as well as the activation energy for the guest system. The filamentary texture was observed by polarized light optical microscopy for both the pure and Schiff base-doped 5CB.

Graphical Abstract

Keywords:

• Liquid crystal
• nematic-isotropic transition
• guest–host effect
• azomethine compound
• order parameter
• activation energy

Acknowledgements

The authors gratefully acknowledge the support of « la Direction Générale de la Recherche Scientifique et du Développement Technologique d’Algérie » for sponsoring this work. The authors are thankful to the Doctors R.C. Hiorns and A. Khoukh (University of Pau & Pays Adour, UPPA, Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Matériaux) for NMR analysis and Dr Salima Saidi-Besbes (Université Oran 1 Ahmed Benbella) for carrying out MOP observations.

Disclosure statement

The authors report there are no competing interests to declare.