Molecular motions in liquid crystal BBBA (4O.4): QENS study Original Research Article

Molecular rotational motions in butyloxybenzylidine butylanilene as studied by quasielastic neutron scattering technique in the smectic B and smectic A phases are reported. The end chain (butyl group) and the core of the liquid crystal are found to undergo rotational motions, independent of each other. Both of these are best described by the jump rotation, with N=12 equivalent sites on a circle or uniaxial rotational diffusion. Reorientation times, τ1, equal to 6.1×10−11±1.6×10−11 and 1.8×10−11±0.6×10−11 s are obtained for the core group and end chain, respectively, in the smectic B phase. The geometry of rotation has been found to be unchanged in the smectic A phase and the corresponding reorientation times equal to 4.1×10−11±1.2×10−11 and 1.6×10−11±0.5×10−11 s, respectively, are obtained.