Synthesis and liquid crystalline properties of hydrazide derivatives: hydrogen bonding, molecular dipole, and smectic structures

Abstract

A series of dissymmetric hydrazide derivatives with amino terminal group, N‐(4‐alkoxybenzoyl)‐N′‐(4′‐aminobenzoyl) hydrazine (Cn‐NH₂, n indicates the number of carbon atoms), were designed and synthesised, and their liquid crystalline properties were investigated by means of differential scanning calorimetry, polarised optical microscopy, and wide‐angle X‐ray diffraction. It was found that these materials showed a SmA_d phase, and intermolecular hydrogen bonding was confirmed as the driving force. Moreover, these results were further compared with those of their parent compounds, N‐(4‐alkoxybenzoyl)‐N′‐(4′‐nitrobenzoyl) hydrazine (Cn‐NO₂) and the dimers, α, ω‐bis [N‐(4‐nitrobenzoyl)‐N′‐(benzoyl‐4′‐oxy) hydrazine] alkane (Nn), and the effect of hydrogen bonding, dipole‐dipole interactions on the smectic structures is discussed.

Keywords:

• hydrogen bonding
• semi‐bilayer structure
• smectic phase
• hydrazide derivatives
• dipole–dipole interaction

Acknowledgements

Author Dr. Haitao Wang would like to thank Professor Noel A. Clark, Dr. Edgardo Garcia, Renfan Shao, and Chenhui Zhu for their helpful discussions. The authors would like to thank the referees for their valuable comments. Also, 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.