²H NMR and X-Ray Studies of a Substance Exhibiting Crystal-Like Smectic Phases

Abstract

DSC, polarizing optical microscopy and X-ray diffractometry were used to investigate the mesomorphic behaviour of 4-n-butyl-4′-acetyl-biphenyl, which resulted to exhibit a smectic E and, possibly, a smectic K phase. Additionally, ²H NMR spectroscopy was applied on a selectively deuterated sample to study the properties of alignment of the mesophases within a magnetic field, as well as to characterize molecular dynamics. Two motional processes were found to be active in the smectic E phase, namely fast π-flips of the benzene rings and molecular self-diffusion about the herringbone bidimensional lattice of the layers. No molecular overall diffusional motions were observed by either ²H NMR spectroscopy or dielectric relaxation measurements.

Keywords:

• 4-n-butyl-4′-acetyl-biphenyl
• deuterium NMR
• dielectric spectroscopy
• smectic E phase
• smectic K phase
• X-ray

Acknowledgments

This work was partially supported by the executive programme of scientific and technological co-operation between the Italian Republic and the Republic of Poland 2004–2006 (project no. 10).