Thermal analysis of hydrogen bonded benzoic acid liquid crystals

• Published in: Journal of thermal analysis and calorimetry Vol. 113; no. 2; pp. 811 - 820
• Main Authors: Sathya Prabu, N. Pongali, Madhu Mohan, M. L. N.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.08.2013; Springer
• Subjects: Acetal resins; Analytical Chemistry; Benzoic acid; Calorimetry; Chemistry; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Differential scanning calorimetry; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Hydrogen; Hydrogen bonding; Infrared spectroscopy; Inorganic Chemistry; Liquid crystals; Measurement Science and Instrumentation; Order disorder; Organic acids; Phase diagrams; Physical Chemistry; Physics; Polymer Sciences; Power law; Specific phase transitions; Thermal analysis; Transitions in liquid crystals; Order of phase transition; Tilt angle; Binary mixtures; Supramolecular hydrogen bonded liquid crystals; Smectic X; Phase transformations; Liquid crystals; Inclination; Benzoic acid derivatives; Hydrogen bonds; Supramolecular structure; Homologous series; Property structure relationship; Thermal analysis
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-012-2812-6

Novel homologous series of supramolecular hydrogen bonded liquid crystals have been investigated. Hydrogen bonds are formed between p-n octyloxy benzoic acid and various p-n alkyloxy benzoic acids whose carbon chain length varied from pentyl to dodecyl. These complexes are characterized by Fourier transform infrared spectroscopy, polarizing optical microscopy (POM), and differential scanning calorimetry (DSC). Phase diagram is constructed from POM and DSC data. The order of the phase transitions is determined by Navard and Cox ratio ( N R ). Characteristic phases like nematic, smectic C, and smectic F are identified. A new smectic ordering observed in this series is investigated by constructing phase diagram obtained from two binary mixtures of the present homologs. Inter-digitation of lamellar layers is observed to be one of the reasons for the occurrence of new smectic ordering. Optical tilt angle in smectic C phase is fitted to a power law. The magnitude of exponent of the power law is found to concur with the Mean Field theory predicted value.