Conformational studies of intermolecular hydorgen bonding through induced crystal G phase in nBA:7HB

Abstract

This paper exploits the physical investigation on liquid crystal complexes obtained by self-organisation of p-n-alkyl benzoic acid (nBA) mesogens with non-mesogenic materials heptyl p-hydroxy benzoate (7HB). Intermolecular interactions of the molecules result the hydrogen bond between the proton donor (COOH) of nBA and proton acceptor (OH) of 7HB. The formation of hydrogen bond is attributed to the quenching of the nematic phase and inducement of crystal G phase in liquid crystal complex. A comparative study of phase abundance is presented with respect to the pure nBAs and other hydrogen bonded liquid crystal complexes of nBAs. Thermal and phase behaviour of the complexes are determined by polarising optical microscope (POM), differential scanning calorimetry (DSC) and image moments approach. Intermolecular interactions which result the hydrogen bond in complexes are investigated using Fourier transform infrared (FTIR) spectroscopy. Molecular structure of the liquid crystal complexes in the solid phase was elucidated using powder X-ray diffraction and proton nuclear magnetic resonance (¹HNMR).

Keywords:

• alkyl benzoic acids
• polarising optical microscope
• textures
• phase transitions
• image analysis
• hydrogen bond
• FTIR
• X-ray diffraction
• ¹HNMR

Acknowledgements

The authors gratefully acknowledge UGC DRS LEVEL III program No. F.530/1/DRS/2009 (SAP-1), dated 9 February 2009, and DST FIST program No. DST/FIST/PSI – 002/2011 dated 20 December 2011, New Delhi, to the department of Physics, ANU for providing financial assistance.