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Design, synthesis and characterization of a linear hydrogen bonded homologous series
Authors:C. KavithaN. Pongali Sathya Prabu  M.L.N. Madhu Mohan
Affiliation:Liquid Crystal Research Laboratory (LCRL), Bannari Amman Institute of Technology, Sathyamangalam 638401, India
Abstract:A linear hydrogen bonded liquid crystalline homologous series has been synthesized and characterized. Hydrogen bond is formed between p-n-dodecyloxy benzoic acid and various p-n-alkyl benzoic acids whose alkyl chain vary from octyl to ethyl. Synthesized complexes are characterized by FTIR, 1H NMR and 13C NMR studies for inferring the formation of hydrogen bonds. Polarizing Optical Microscopy (POM) and DSC studies reveal various mesophases and their corresponding transition temperatures along with respective enthalpy values. All the seven synthesized complexes exhibit rich liquid crystalline mesomorphism. A new phase namely smectic X has been observed in five of the complexes with a narrow thermal range. This phase has been characterized by optical textural, DSC, tilt angle and helicoidal pitch studies. Smectic X is sandwiched between traditional smectic C and re-entrant smectic C (designated as CR) phases. Homeotropic transition in nematic phase is observed in all the mesogens and thus these materials can be used as thermally controlled optical shutters. Tilt angle in smectic C, smectic X and smectic CR phases have been experimentally elucidated for all the mesogens.
Keywords:Hydrogen bonded liquid crystals   Smectic X   Re-entrant smectic C   Homeotropic transition   Thermally controlled optical shutter
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