Molecular Dynamics of p-Brome-p-n- Hexyloxybenzylidene Aniline in the Smectic B Phase by Proton NMR Relaxation

Abstract

The dynamics of a smectic B phase is studied for the p-brome-p-n-hexyloxybenzylidene aniline (6Br) by the proton NMR technique. The proton spin lattice relaxation time has been measured as a function of frequency and as a function of temperature over the whole mesomorphic phases and in the isotropic phase up to 14 C above the clearing point. The relaxation measurements for the smectic B phase are discussed in terms of potential contributions of various molecular motions, but translational self-diffusion and rotations/reorientions explain well the relaxation. In the high frequency limit the relaxation is dominated by rotations/reorientations while the translational self diffusion is dominant in the low frequency region. The results reflect the particular distribution of asymmetric molecules in the smectic layers.

Keywords:

• molecular dynamics
• smectic B
• NMR relaxation