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Abstract
Liquid crystal trimers based on the hydrogen bonding dimerization of 4‐{n‐[4‐(4‐m‐alkoxy‐phenylazo)phenoxy]alkoxy}benzoic acid (BAm‐n) have been synthesized and characterized. Temperature‐dependent FTIR spectroscopic studies showed that the carboxylic acid groups in BAm‐n are associated to form H‐bonded cyclic dimers both in their crystalline and liquid crystalline phases. The trimers exhibited enantiotropic liquid crystalline behaviour except for BA1‐3 which showed monotropic behaviour, and the mesophases changed from nematic to smectic phase, with the increase of length of the spacer and the terminal substituents. Pronounced odd–even effects in the melting temperatures, clearing temperatures and nematic–isotropic enthalpy changes were observed.
Acknowledgements
The authors are grateful to the National Science Foundation Committee of China (project No. 50373016), Program for New Century Excellent Talents in Universities of China Ministry of Education, Special Foundation for PhD Program in Universities of China Ministry of Education (Project No. 20050183057) and Project 985‐Automotive Engineering of Jilin University for their financial support of this work.