Mesomorphic Behavior of Symmetrical and Unsymmetrical Azomethines with Two Imine Groups

• Published in: Materials Vol. 2; no. 1; pp. 38 - 61
• Main Authors: Iwan, Agnieszka, Janeczek, Henryk, Jarzabek, Bozena, Rannou, Patrice
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2009; Molecular Diversity Preservation International
• Subjects: Behavior; Carbon; Hydrocarbons; Investigations; liquid crystals; Microscopy; nematic and smectic phases; Polymorphism; Schiff bases; Symmetrical and unsymmetrical azomethines
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma2010038

Seven symmetrical azomethines with two imine groups (HC=N) were synthesized by condensation of the benzene-1,4-dicarboxaldehydewith five amines (first group: A1-A5) and of the 2,5-thiophenedicarboxaldehyde with two amines (second group: AT1-AT2). Additionally, two unsymmetrical azomethines were obtained by a two step condensation of benzene-1,4-dicarboxaldehydewith pyren-1-amine(1st step) (abbreviated hereinafter as AP1) and then AP1 was reacted with4-dodecylaniline or 4-hexadecylaniline (2nd step) (third group: AP1A-AP1B). Liquid crystalline properties of the azomethines were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and UV-vis spectroscopy in the function of temperature [UV-vis(T)]. The Wide-Angle X-ray Diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Mesomorphic behavior was observed for symmetrical and unsymmetrical azomethines, obtained from the benzene-1,4-dicarboxaldehyde and symmetrical ones prepared from 2,5-thiophenedicarboxaldehyde and different amineshaving aliphatic chains. Based on the POM and DSC measurements the following mesophases were detected: nematic, smectic A, smectic C, smectic F (I), smectic G (J).